"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:9ad4f1f3-97df-4c57-a3ce-5a2baa9fff40","http://resolver.tudelft.nl/uuid:9ad4f1f3-97df-4c57-a3ce-5a2baa9fff40","Local Reaction Environment Deviations within Gas Diffusion Electrode Pores for CO2 Electrolysis","Butt, E.N. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing); Hartkamp, Remco (TU Delft Complex Fluid Processing)","","2024","The local conditions inside a gas diffusion electrode (GDE) pore, especially in the electrical double layer (EDL) region, influence the charge transfer reactions and the selectivity of desired CO2ER products. Most GDE computational models ignore the EDL or are limited in their applicability at high potentials. In this work, we present a continuum model to describe the local environment inside a catalytic pore at varying potentials, electrolyte concentrations and pore diameters. The systems studied in this work are based on an Ag catalyst in contact with KHCO3 solution. Our study shows that steric effects dominate the local environment at high cathodic potentials (≪−25 mV vs pzc at the OHP), leading to a radial drop of CO2 concentration. We also observe a drop in pH value within 1 nm of the reaction plane due to electrostatic repulsion and attraction of OH− and H+ ions, respectively. We studied the influence of pore radii (1-10 nm) on electric field and concentrations. Pores with a radius smaller than 5 nm show a higher mean potential, which lowers the mean CO2 concentration. Pores with a favourable local environment can be designed by regulating the ratio between the pore radius and Debye length.","CO electrochemical reduction; gas diffusion electrode; lectric double layer; modelling; steric effects","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:7bc0145f-3e4b-4947-9617-9f71462394be","http://resolver.tudelft.nl/uuid:7bc0145f-3e4b-4947-9617-9f71462394be","A 0D Model for the Comparative Analysis of Hydrogen Carriers in Ship’s Integrated Energy Systems","Van Rheenen, E.S. (TU Delft Ship Design, Production and Operations); Padding, J.T. (TU Delft Complex Fluid Processing); Visser, K. (TU Delft Ship Design, Production and Operations)","","2024","Hydrogen carriers are attractive alternative fuels for the shipping sectors. They are zero-emission, have high energy densities, and are safe, available, and easy to handle. Sodium borohydride, potassium borohydride, dibenzyltoluene, n-ethylcarbazole, and ammoniaborane are interesting hydrogen carriers, with high theoretical energy densities. The exact energy density of these hydrogen carriers depends on the integration of heat and mass with the energy converters. This combination defines the energy efficiency and, thus, the energy density of the system. Using a 0D model, we combined the five carriers with two types of fuel cells (PEM and SOFC), an internal combustion engine and a gas turbine. This resulted in 20 combinations. Despite the limitations of the 0D model and the occasional difficulty of validating input values, this model still produces exciting findings, which are valuable for further research. For the dehydrogenation of both dibenzyltoluene and n-ethylcarbazole, an external hydrogen burner is required if no waste heat resources from the integrated system are available. For the borohydrides, on the other hand, energy integration is essential for reducing cooling power. Dehydrogenation produces substantial energy, but only a fraction of this energy can be used for internal preheating. Dehydrogenation of ammoniaborane produces less energy. Among all hydrogen carriers, both ammoniaborane and sodium borohydride provide energy densities comparable to that of marine diesel oil. In particular, ammoniaborane possesses a remarkably high energy density. Thus, we conclude, that hydrogen carriers are attractive alternative fuels that deserve more attention, including their potential performance for hydrogen imports.
D) of a single sphere subjected to uniform fluid flow consists of a series of logarithmic and power terms of the Reynolds number (Re). In this paper, we will explore the validity of the above statement for Reynolds numbers up to 106 by using a symbolic regression machine learning method. The algorithm is trained by available experimental data and data from well-known correlations from the literature for Re ranging from 0.1 to 2×105. Our results show that the functional form of CD contains powers of log(Re), plus the Stokes term. The logarithmic CD expressions can generalize (extrapolate) better beyond the training data than pure power series of Re and are the first in the literature to predict with acceptable accuracythe onset of the rapid decrease (drag crisis) of CD at high Re, but also to follow the right behaviour towards zero Re. We also find a connection between the root of the Re-dependent terms in the CD expression and the first point of laminar separation. The generalization behaviour of power-based drag coefficient equations is worse than logarithmic-based ones, especially towards the zero Re regime in which they give non-physical results. The logarithmic based CD correctly describes the physics from the low Re regime to the onset of the drag crisis. Also, by applying a minor modification in the logarithmic based equations, we can predict the drag coefficient of an oblate spheroid in the high Re regime.","Drag coefficient; Machine learning; Matched asymptotic expansions; Multi-phase flows; sphere","en","journal article","","","","","","","","","","","Offshore Engineering","","",""
"uuid:a67a6d68-3868-4ace-ae7f-358491f521f7","http://resolver.tudelft.nl/uuid:a67a6d68-3868-4ace-ae7f-358491f521f7","A note on the modelling of lubrication forces in unresolved simulations","Nijssen, Tim M.J. (TU Delft BT/Bioprocess Engineering); Ottens, M. (TU Delft BT/Design and Engineering Education); Padding, J.T. (TU Delft Complex Fluid Processing)","","2023","Lubrication forces play a major role in the behaviour of fluid–solid systems, where they affect the collisions between particles. Current implementations of lubrication forces in unresolved simulations often suffer from shortcomings, such as neglecting parts of the physics or relying on arbitrarily defined parameters. In this short communication, we propose a novel implementation, rigorously defined based on physical and numerical factors. Both particle roughness and deformation are considered, and the model accuracy is demonstrated through comparison with experimental results.","CFD-DEM; Fluid–solid systems; Lubrication force; Multiphase modelling; Unresolved simulations","en","journal article","","","","","","","","","","","BT/Bioprocess Engineering","","",""
"uuid:da431fc4-7e8e-40bb-85d8-3035909127ca","http://resolver.tudelft.nl/uuid:da431fc4-7e8e-40bb-85d8-3035909127ca","Inhomogeneities in the Catholyte Channel Limit the Upscaling of CO2 Flow Electrolysers","Blake, J.W. (TU Delft Complex Fluid Processing); Konderla, V. (TU Delft ChemE/Transport Phenomena); Baumgartner, L.M. (TU Delft ChemE/Transport Phenomena); Vermaas, D.A. (TU Delft ChemE/Transport Phenomena); Padding, J.T. (TU Delft Complex Fluid Processing); Haverkort, J.W. (TU Delft Energy Technology)","","2023","The use of gas diffusion electrodes that supply gaseous CO2 directly to the catalyst layer has greatly improved the performance of electrochemical CO2 conversion. However, reports of high current densities and Faradaic efficiencies primarily come from small lab scale electrolysers. Such electrolysers typically have a geometric area of 5 cm2, while an industrial electrolyser would require an area closer to 1 m2. The difference in scales means that many limitations that manifest only for larger electrolysers are not captured in lab scale setups. We develop a 2D computational model of both a lab scale and upscaled CO2 electrolyser to determine performance limitations at larger scales and how they compare to the performance limitations observed at the lab scale. We find that for the same current density larger electrolysers exhibit much greater reaction and local environment inhomogeneity. Increasing catalyst layer pH and widening concentration boundary layers of the KHCO3 buffer in the electrolyte channel lead to higher activation overpotential and increased parasitic loss of reactant CO2 to the electrolyte solution. We show that a variable catalyst loading along the direction of the flow channel may improve the economics of a large scale CO2 electrolyser.","CO reduction; electrolysis; gas diffusion electrode; parasitic reactions; scale up; variable catalyst loading","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:16b0753f-43d8-4c9e-9ca0-4978871757cb","http://resolver.tudelft.nl/uuid:16b0753f-43d8-4c9e-9ca0-4978871757cb","A Review of Laser-Induced Crystallization from Solution","Korede, V.B. (TU Delft Complex Fluid Processing); Nagalingam, Nagaraj (TU Delft Complex Fluid Processing); Penha, Frederico Marques (KTH Royal Institute of Technology); van der Linden, Noah (Student TU Delft); Padding, J.T. (TU Delft Complex Fluid Processing); Hartkamp, Remco (TU Delft Complex Fluid Processing); Eral, H.B. (TU Delft Complex Fluid Processing)","","2023","Crystallization abounds in nature and industrial practice. A plethora of indispensable products ranging from agrochemicals and pharmaceuticals to battery materials are produced in crystalline form in industrial practice. Yet, our control over the crystallization process across scales, from molecular to macroscopic, is far from complete. This bottleneck not only hinders our ability to engineer the properties of crystalline products essential for maintaining our quality of life but also hampers progress toward a sustainable circular economy in resource recovery. In recent years, approaches leveraging light fields have emerged as promising alternatives to manipulate crystallization. In this review article, we classify laser-induced crystallization approaches where light-material interactions are utilized to influence crystallization phenomena according to proposed underlying mechanisms and experimental setups. We discuss nonphotochemical laser-induced nucleation, high-intensity laser-induced nucleation, laser trapping-induced crystallization, and indirect methods in detail. Throughout the review, we highlight connections among these separately evolving subfields to encourage the interdisciplinary exchange of ideas.","","en","review","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:508e1ae7-a716-4576-b8c5-bf82ad9be3f2","http://resolver.tudelft.nl/uuid:508e1ae7-a716-4576-b8c5-bf82ad9be3f2","Hydrodynamics of expanded bed adsorption studied through CFD-DEM","Nijssen, Tim M.J. (TU Delft Engineering Thermodynamics); Padding, J.T. (TU Delft Complex Fluid Processing); Ottens, M. (TU Delft BT/Design and Engineering Education)","","2023","The hydrodynamics of the Expanded Bed Adsorption process is studied through simulations combining Computational Fluid Dynamics and the Discrete Element Method. A representative base case is defined, based on process design parameters commonly encountered in literature. Then, 19 other cases are defined, each representing a singular adjustment to the column design, material properties, or operating conditions. The parameters that are varied are the expansion factor, liquid viscosity, bed aspect ratio, mean particle density, width of the particle density distribution, width of the particle size distribution, column taper angle, and column alignment angle. The impact of each adjustment on the bed behaviour is discussed, using the local particle size distribution and solids dispersion coefficient as main indicators of bed stability. Optimal performance was found for an expansion factor of two to three, and the combination of particle size distribution and particle density distribution was found to greatly improve bed stability. The mixing process of the liquid and solid phases is concluded to be of highly complex nature, and cannot simply be predicted from the liquid flow velocity.","Computational fluid dynamics; Discrete element method; Expanded bed adsorption; Hydrodynamics; Liquid-solid fluidisation","en","journal article","","","","","","Funding Information: This work was supported by the Dutch Research Council NWO [grant number 729.001.002 ], and made use of the Dutch national e-infrastructure with the support of the SURF Cooperative [grant number EINF-3414 ].","","","","","Engineering Thermodynamics","","",""
"uuid:405d66fd-be30-43ab-bab8-5eb382719aec","http://resolver.tudelft.nl/uuid:405d66fd-be30-43ab-bab8-5eb382719aec","Thermodynamic and Transport Properties of H2/H2O/NaB(OH)4 Mixtures Using the Delft Force Field (DFF/B(OH)4-)","Habibi, P. (TU Delft Engineering Thermodynamics); Postma, J.R.T. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing); Dey, P. (TU Delft Team Poulumi Dey); Vlugt, T.J.H. (TU Delft Engineering Thermodynamics); Moultos, O. (TU Delft Engineering Thermodynamics)","","2023","Sodium borohydride (NaBH4) has a high hydrogen (H2 ) gravimetric capacity of 10.7 wt %. NaBH4 releases H2 through a hydrolysis reaction in which aqueous NaB(OH)4 is formed as a byproduct. NaB(OH)4 strongly influences the thermophysical properties of aqueous solutions (i.e., densities, viscosities, and electrical conductivities) and the hydrolysis reaction kinetics and conversion of NaBH4. Here, molecular dynamics (MD) simulations are performed to compute viscosities, electrical conductivities, and self-diffusivities of H2 , Na+, and B(OH)4- for a temperature and concentration range of 298-353 K and 0-5 mol NaB(OH)4/kg water, respectively. Continuous fractional component Monte Carlo (CFCMC) simulations are used to compute the solubilities of H2 and activities of water in aqueous NaB(OH)4 solutions for the same temperature and concentration range. A new force field is developed (Delft force field of B(OH)4-: DFF/B(OH)4-) in which B(OH)4- is modeled as a tetrahedral structure with a scaled charge of −0.85. The OH group in B(OH)4- is modeled as a single interaction site. This force field is based on TIP4P/2005 water and the Madrid-2019 Na+ force field. The MD simulations can accurately capture the densities and viscosities within 2.5% deviation from available experimental data at 298 K up to a concentration of 5 mol NaB(OH)4/kg water. The computed electrical conductivities deviate by ca. 10% from experimental data at 298 K for the same concentration range. Based on the molecular simulations results, engineering equations are developed for shear viscosities, self-diffusivities of H2, Na+, and B(OH)4-, and solubilities of H2, which can be used to design and model NaBH4 hydrolysis reactors.","","en","journal article","","","","","","","","","","","Engineering Thermodynamics","","",""
"uuid:c950f39c-0f4c-43a0-bd01-ddb523303968","http://resolver.tudelft.nl/uuid:c950f39c-0f4c-43a0-bd01-ddb523303968","A review of the potential of hydrogen carriers for zero emission, low signature ship propulsion systems","Van Rheenen, E.S. (TU Delft Ship Design, Production and Operations); Padding, J.T. (TU Delft Complex Fluid Processing); Slootweg, J.C. (Universiteit van Amsterdam); Visser, K. (TU Delft Ship Design, Production and Operations)","","2022","Increasing pressure on the reduction or elimination of the use of fossil fuels in shipping requires the application of new maritime fuel alternatives. Green and circular produced hydrogen as a maritime fuel in fuel cell systems offers a great solution for these concerns. A fuel cell system has a zero emission performance, solid state silent process cycle, graceful degradation and no single point of failure. From a naval perspective, these characteristics very much support operational requirements like a silent propulsion and very low thermal and acoustic signatures as well as the possibility of an air independent system. Storage of hydrogen, however, is an issue. Traditional hydrogen storage in gas or liquefied aggregation has low volumetric density, low flame point, fire and explosion risks and transport challenges. The aim of this literature review is to investigate several hydrogen carriers and evaluate their characteristics on maritime and naval performance. This includes their volumetric and gravimetric density, dehydrogenation process, safety, logistic availability and handling. Over 15 different (types of) hydrogen carriers have been researched. Borohydrides, specifically sodium borohydride appeared to have several advantages, but still has issues with its hydrogenation process and handling due to it being a solid. The liquid organic hydrogen carrier dibenzyl toluene, on the other hand, does not meet the required energy density, but does have favourable additional properties, such as easy hydrogenation and good handling. Both of these are also subject of current research and development: For example, Hydrogenious LOHC Maritime AS, in combination with �stensj? Rederi, is working on a megawatt application for maritime, which should be finished in 2025. The Dutch government funds the SH2IPDRIVE project and the European Interreg North West Europe organization funds the H2SHIPS research project to analyse the shipboard use of these hydrogen carriers and to establish the design and engineering optimization opportunities.","Hydrogen; hydrogen carriers; Solid hydrogen carriers; Liquid hydrogen carriers; Maritime transportation","en","conference paper","IMarEST","","","","","","","","","","Ship Design, Production and Operations","","",""
"uuid:ef50498a-5408-4808-846f-0ad087a68eb7","http://resolver.tudelft.nl/uuid:ef50498a-5408-4808-846f-0ad087a68eb7","Two phase modelling of Geldart B particles in a novel indirectly heated bubbling fluidized bed biomass steam reformer","Tsekos, C. (TU Delft Large Scale Energy Storage); de Voogt, D.; de Jong, W. (TU Delft Large Scale Energy Storage); Padding, J.T. (TU Delft Complex Fluid Processing)","","2022","This work focuses on the numerical modelling and experimental validation of the hydrodynamic behaviour of a novel 50 kWth indirectly heated bubbling fluidized bed steam reformer. The hydrodynamic behaviour of fluidized beds with immersed vertical tubes and complex fluidized bed geometries in general have not been thoroughly investigated in terms of numerical modelling coupled with experimental validation for pilot scale reactors. Therefore, the present study contributes to the fluidized bed hydrodynamics numerical modelling field, while investigating a novel reactor concept. Simulations were performed employing the Two-Fluid Model approach, using the Kinetic Theory of Granular Flows (KTGF) and the adjusted Syamlal O'Brien drag model. The reactor's hydrodynamic behaviour was simulated successfully, as showcased by a comparison of global hydrodynamic metrics (bed height, pressure drop) between computational and experimental results. Simulations were performed with and without considering an additional nitrogen gas feed on the side of the reactor (feeding system pressurization). Overall, for both cases, for realistic values of the particle restitution coefficient channelling of the gas flow near the reactor walls was observed. Larger bubbles appeared to be forming near the outer wall of the reactor for the no side-flow simulations. The opposite behaviour was encountered for the side-flow simulations due to stream-like behaviour of the side-flow moving up against the reactor's outer wall. The choice to limit the simulations to a 72° symmetry domain was validated, indicating the possibility of further reduction. Finally, it was argued that increasing the reactor's diameter could potentially lead to a reduction of the observed channelling of the fluidization media and improve the mixing achieved in the reactor and thus the conversion efficiency of the IHBFBSR during gasification applications.","Allothermal; CFD; Fluidized bed; Gasification; Non-standard geometry; TFM","en","journal article","","","","","","","","","","","Large Scale Energy Storage","","",""
"uuid:2e9033ee-1e79-4244-8d90-cc4a19554ef1","http://resolver.tudelft.nl/uuid:2e9033ee-1e79-4244-8d90-cc4a19554ef1","Coupling mesoscale transport to catalytic surface reactions in a hybrid model","Fan, R. (TU Delft Complex Fluid Processing); Habibi, P. (TU Delft Engineering Thermodynamics); Padding, J.T. (TU Delft Complex Fluid Processing); Hartkamp, Remco (TU Delft Complex Fluid Processing)","","2022","In heterogeneous catalysis, reactivity and selectivity are not only influenced by chemical processes occurring on catalytic surfaces but also by physical transport phenomena in the bulk fluid and fluid near the reactive surfaces. Because these processes take place at a large range of time and length scales, it is a challenge to model catalytic reactors, especially when dealing with complex surface reactions that cannot be reduced to simple mean-field boundary conditions. As a particle-based mesoscale method, Stochastic Rotation Dynamics (SRD) is well suited for studying problems that include both microscale effects on surfaces and transport phenomena in fluids. In this work, we demonstrate how to simulate heterogeneous catalytic reactors by coupling an SRD fluid with a catalytic surface on which complex surface reactions are explicitly modeled. We provide a theoretical background for modeling different stages of heterogeneous surface reactions. After validating the simulation method for surface reactions with mean-field assumptions, we apply the method to non-mean-field reactions in which surface species interact with each other through a Monte Carlo scheme, leading to island formation on the catalytic surface. We show the potential of the method by simulating a more complex three-step reaction mechanism with reactant dissociation.","","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2022-08-22","","","Complex Fluid Processing","","",""
"uuid:c94a33d2-aff0-4989-86f0-1901d9a19b2a","http://resolver.tudelft.nl/uuid:c94a33d2-aff0-4989-86f0-1901d9a19b2a","Accurate hydrodynamic force and torque correlations for prolate spheroids from Stokes regime to high Reynolds numbers","Sanjeevi, Sathish K.P. (National Energy Technology Laboratory); Dietiker, Jean F. (National Energy Technology Laboratory); Padding, J.T. (TU Delft Complex Fluid Processing)","","2022","Detailed simulations of flow around various prolate spheroids are performed using multi-relaxation time lattice Boltzmann method (LBM). The simulations are performed in the Reynolds numbers range 0.1≤Re≤2000 at different incident angles 0∘≤ϕ≤90∘ for various prolate spheroids of aspect ratios 1≤λ≤8. The Re is based on the volume equivalent sphere diameter. From the simulations, accurate correlations for average drag, lift and torque coefficients (CD, CL, and CT respectively) are proposed. The mean deviations between the correlations and the simulation data for CD, CL, and CT are 2%, 6.5%, and 4.7% respectively. Furthermore, the correlations are fitted with the physics in mind such that they can be extrapolated beyond the regimes simulated. The fits are designed such that correlations reduce to analytical (CD and CL) solutions available for prolate spheroids in the limit Re≈0. At high Re, the correlations mimic the asymptotic flattening of CD as for spheres and therefore, we expect the correlations to be valid until the critical Re (≈105). Furthermore, extensive comparison of our correlations with other high-fidelity simulations from literature demonstrate the accuracy of our work compared to other correlations from literature. This work enables researchers to perform accurate unresolved Euler-Lagrangian simulations for a wide range of elongated particles.","Drag, lift, and torque correlations; Lattice Boltzmann method; Non-spherical particles","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:86ded059-79cb-4933-809d-565aff845bd3","http://resolver.tudelft.nl/uuid:86ded059-79cb-4933-809d-565aff845bd3","New hydraulic insights into rapid sand filter bed backwashing using the Carman–Kozeny model","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht; Queen Mary University of London); de Moel, P.J. (TU Delft Sanitary Engineering; Waternet; Omnisys); Padding, J.T. (TU Delft Complex Fluid Processing); Baars, Eric T. (Waternet); Rutten, Sam B. (Hogeschool Utrecht; Wetsus, European Centre of Excellence for Sustainable Water Technology); Elarbab, Awad H.E. (Hogeschool Utrecht); Hooft, Jos F.M. (Waternet); Boek, Edo S. (Queen Mary University of London); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2021","Fluid flow through a bed of solid particles is an important process that occurs in full-scale water treatment operations. The Carman–Kozeny model remains highly popular for estimating the resistance across the bed. It is common practice to use particle shape factors in fixed bed state to match the predicted drag coefficient with experimentally obtained drag coefficients. In fluidised state, however, where the same particles are considered, this particle shape factor is usually simply omitted from the model without providing appropriate reasoning. In this research, it is shown that a shape factor is not a constant particle property but is dependent on the fluid properties as well. This dynamic shape factor for irregularly shaped grains increases from approximately 0.6 to 1.0 in fluidised state.
We found that unstable packed beds in moderate up-flow conditions are pseudo-fixed and in a setting state. This results in a decreasing bed voidage and simultaneously in a decreasing drag coefficient, which seems quite contradictory. This can be explained by the collapse of local channels in the bed, leading to a more uniform flow distribution through the bed and improving the available surface for flow-through. Our experimental measurements show that the drag coefficient decreases considerably in the laminar and transition regions. This is most likely caused by particle orientation, realignment and rearrangement in particles’ packing position.
A thorough hydraulic analysis shows that up-flow filtration in rapid sand filters under backwash conditions causes the particle bed to collapse almost imperceptibly. In addition, an improved expression of the drag coefficient demonstrated that the Carman–Kozeny model constant, however often assumed to be constant, is in fact not constant for increasing flow rates. Furthermore, we propose a new pseudo-3D image analysis for particles with an irregular shape. In this way, we can explain the successful method using optimisation of the extended terminal sub-fluidisation wash (ETSW) filter backwashing procedure, in which turbidity and peaks in the number of particles are reduced with a positive effect on water quality.","Drinking Water Treatment; Multiphase Flows; Filter-Backwash; Hydraulics Drag Relations; Particle Orientation; Dynamic Particle Shape Factors","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:0d76934d-cbc7-4294-a773-6b9d9eef5be6","http://resolver.tudelft.nl/uuid:0d76934d-cbc7-4294-a773-6b9d9eef5be6","Experimental and numerical insights into heterogeneous liquid-solid behaviour in drinking water softening reactors","Nijssen, T.M.J. (Eindhoven University of Technology); Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht; Queen Mary University of London); de Moel, P.J. (Waternet; Omnisys); Rahman, J. (Queen Mary University of London); Kroon, J.P. (Eindhoven University of Technology); Berhanu, P. (Queen Mary University of London); Boek, E.S. (Queen Mary University of London); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet); Padding, J.T. (TU Delft Complex Fluid Processing)","","2021","Liquid-solid fluidisation is frequently encountered in drinking water treatment processes, for instance in seeded crystallisation softening processes. For modest superficial fluid velocities, liquid–solid fluidisation systems are generally considered to be homogeneous, as reported in literature. However, during fluidisation experiments with calcite grains, open spaces of water can be observed between the fluidised particles, even at relatively low fluid velocities. Moreover, significant heterogeneous particle–fluid patterns are detected at higher fluid velocities. Such heterogeneous behaviour can beneficially or adversely affect the chemical crystallisation efficiency. To obtain information about voids in bulk regions, complementary Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) simulations were performed and compared with the experimental results for validation. Simulations were performed using different water inlet velocities and fractionised calcite granules obtained from full-scale reactors. Here, the results are analysed using the bed height, voidage and pressure drop of the system. Furthermore, images of the experiments and simulations are visually compared for the formation of voids. The simulations showed distinct differences in void fraction in the cross-section of the column. It is shown that throughout the range of considered water velocities, heterogeneous behaviour exists and cannot be neglected. The heterogeneity and onset of fluidisation behaviour obtained from the simulations and experimental observations were compared and found to agree reasonably well.","Fluidisation; Unsteady behaviour; Drinking water treatment; Multiphase computational fluid dynamics; Reactor performance; Void fraction distribution","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:0ff591bf-b113-4f46-9fd0-2cddb9b4cacc","http://resolver.tudelft.nl/uuid:0ff591bf-b113-4f46-9fd0-2cddb9b4cacc","A novel sensor measuring local voidage profile inside a fluidised bed reactor","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht; Queen Mary University of London); van Schaik, C. (Waternet; Hogeschool Utrecht); Hangelbroek, J.J. (Waternet); de Moel, P.J. (TU Delft Sanitary Engineering; Waternet; Omnisys); Colin, M.G. (Waternet); Amsing, M. (Bienfait); Boek, E.S. (Queen Mary University of London); Breugem, W.P. (TU Delft Multi Phase Systems); Padding, J.T. (TU Delft Complex Fluid Processing); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2021","Liquid-solid fluidisation is frequently encountered in drinking water treatment processes, often to obtain a large liquid-solid interfacial surface area. A large surface area is crucial for optimal seeded crystallisation in full-scale softening reactors. Due to crystallisation, particles grow and migrate to a lower zone in the reactor which leads to a stratified bed. Larger particles adversely affect the surface area. To maintain optimal process conditions in the fluidised beds, information is needed about the distribution of particle size, local voidage and available surface area, over the reactor height.
In this work, a sensor is developed to obtain the hydraulic state gradient, based on Archimedes’ principle. A cylindrical heavy object is submerged in the fluidised bed and lowered gradually while its weight is measured at various heights using a sensitive force measuring device.
Based on accurate fluidisation experiments with calcite grains, the voidage is determined and a straightforward empirical model is developed to estimate the particle size as a function of superficial fluid velocity, kinematic viscosity, suspension density, voidage and particle density. The surface area and specific space velocity can be estimated accordingly, which represent key performance indicators regarding the hydraulic state of the fluidised bed reactor. The prediction error for voidage is 5 ± 2 % and for particle size 9 ± 4 %.
The newly developed soft sensor is a more time-effective method for obtaining the hydraulic state in full-scale liquid-solid fluidised bed reactors.","Fluidization; Drinking water treatment; Pellet-softening; Hydrostatic soft sensor; Hydraulic state","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:298d8928-bfed-4274-8462-b92c3dcef42d","http://resolver.tudelft.nl/uuid:298d8928-bfed-4274-8462-b92c3dcef42d","Fluidisation characteristics of granular activated carbon in drinking water treatment applications","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht; Queen Mary University of London); van Schaik, C. (Waternet; Hogeschool Utrecht); Dacomba Torres, P.D.R. (Student TU Delft); de Moel, P.J. (TU Delft Sanitary Engineering); Boek, E.S. (Queen Mary University of London); Baars, E.T. (Waternet); Padding, J.T. (TU Delft Complex Fluid Processing); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2021","Granular activated carbon (GAC) filtration is an important unit operation in drinking water treatment. GAC filtration is widely used for its filtration and adsorption capabilities as a barrier for undesired organic macro- and micro-pollutants. GAC filtration consists of two successive phases: adsorption and filtration, capturing the impurities from the water in conjunction with a backwash procedure in which the suspended particles are flushed out of the system. Available literature predominantly focusses on adsorption. A less frequently discussed but nevertheless equally crucial aspect of this operation is the backwash procedure of GAC beds. To prevent accumulation of suspended particles and to avoid additional operation costs, optimal backwashing is required. Another factor is sustainability: water utilities are showing increasing interest in exploring new sustainable GAC media. As these have different bed expansion tendencies due to different GAC characteristics with varying geometries, operational developments are needed for prediction models to estimate the expansion degree during backwashing. The prediction of the bed expansion of GAC is complex as the particles are non-spherical, porous and polydisperse. Through a combination of advanced particle laboratory and fluidisation experiments, we demonstrate a new approach which leads to an improved expansion prediction model for the backwashing of GAC filters.","Drinking water treatment; Liquid-solid fluidization; Granular activated carbon; Green-based materials; Expansion characteristics; Porosity prediction modelling","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:32e54276-6e69-4899-b60a-ac745a0c42c0","http://resolver.tudelft.nl/uuid:32e54276-6e69-4899-b60a-ac745a0c42c0","Can terminal settling velocity and drag of natural particles in water ever be predicted accurately?","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht); de Moel, Peter J. (Omnisys VOF); Kaveripuram Ramasamy, S.R. (TU Delft Fluid Mechanics); Baars, Eric T. (Waternet); van Vught, Wim H. (Hogeschool Utrecht); Breugem, W.P. (TU Delft Multi Phase Systems); Padding, J.T. (TU Delft Complex Fluid Processing); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2021","Natural particles are frequently applied in drinking water treatment processes in fixed bed reactors, fluidised bed reactors, and sedimentation processes to clarify water and to concentrate solids. When particles settle, it has been found that, in terms of hydraulics, natural particles behave differently when compared to perfectly round spheres. To estimate the terminal settling velocity of single solid particles in a liquid system, a comprehensive collection of equations is available. For perfectly round spheres, the settling velocity can be calculated quite accurately. However, for naturally polydisperse non-spherical particles, experimentally measured settling velocities of individual particles show considerable spread from the calculated average values.
This work aims to analyse and explain the different causes of this spread. To this end, terminal settling experiments were conducted in a quiescent fluid with particles varying in density, size, and shape. For the settling experiments, opaque and transparent spherical polydisperse and monodisperse glass beads were selected. In this study, we also examined drinking-water-related particles, like calcite pellets and crushed calcite seeding material grains, which are both applied in drinking water softening. Polydisperse calcite pellets were sieved and separated to acquire more uniformly dispersed samples. In addition, a wide variety of grains with different densities, sizes, and shapes were investigated for their terminal settling velocity and behaviour. The derived drag coefficient was compared with well-known models such as the one of Brown and Lawler (2003).
A sensitivity analysis showed that the spread is caused, to a lesser extent, by variations in fluid properties, measurement errors, and wall effects. Natural variations in specific particle density, path trajectory instabilities, and distinctive multi-particle settling behaviour caused a slightly larger degree of the spread. In contrast, a greater spread is caused by variations in particle size, shape, and orientation.
In terms of robust process designs and adequate process optimisation for fluidisation and sedimentation of natural granules, it is therefore crucial to take into consideration the influence of the natural variations in the settling velocity when using predictive models of round spheres.","","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:9ace708f-f75f-4c31-a371-7265278acd21","http://resolver.tudelft.nl/uuid:9ace708f-f75f-4c31-a371-7265278acd21","Heat transfer from wall to dense packing structures of spheres, cylinders and Raschig rings","Moghaddam, E.M.C. (TU Delft Mechanical, Maritime and Materials Engineering); Foumeny, E.A.; Stankiewicz, A.I. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2021","This paper investigates the validity of azimuthal averaging of 3D temperature fields in the analysis of lateral heat transfer in dense particle packings. This is conducted by synthetic generation of 3D packing surrogates of spheres, cylinders and Raschig rings with tube-to-pellet diameter ratio, 3 < N < 6, using an in-house Rigid Body Dynamics packing algorithm, followed by detailed discrete pellet CFD simulations of heat transfer from wall to bed for laminar, transient and turbulent flow regimes. The CFD results of hydrodynamics and temperature fields are benchmarked against empirical correlations for pressure drop and interphase heat transfer Nusselt number, Nu, offering the best fits with correlations proposed by Eisfeld and Schnitzlein (for cylinders and spheres) and Nemec and Levec (for rings) for pressure drop, and by Gunn and Sun and coworkers for the prediction of Nu. The CFD results demonstrate that fluctuations in local temperature are completely neglected by azimuthal-averaging of 3D temperature fields over the bed volume, leading to more than 150 °C deviations from the local temperature data. Furthermore, it is found that deviations between azimuthally-averaged axial velocity profile and true local velocities are in an analogous fashion transmitted to the temperature field. This is evidenced by the coincidence of the peaks in the deviation profiles of azimuthally-averaged temperature and velocity from the local data over the bed radius. This is due to thermal disequilibrium between fluid and pellet phases which is partially omitted by the azimuthal-averaging of the 3D temperature field and basically neglected in pseudo-homogenous ker-hw models.","Azimuthal averaging; Cylinders; Fixed beds; Heat transfer; Particle-resolved CFD simulations; Raschig rings; Rigid body dynamics","en","journal article","","","","","","","","","Mechanical, Maritime and Materials Engineering","","Complex Fluid Processing","","",""
"uuid:0682c155-1d11-41f8-8d4c-105e0b38c02a","http://resolver.tudelft.nl/uuid:0682c155-1d11-41f8-8d4c-105e0b38c02a","Analytical modelling of CO2 reduction in gas-diffusion electrode catalyst layers","Blake, J.W. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing); Haverkort, J.W. (TU Delft Energy Technology)","","2021","The electrochemical reduction of CO2 on planar electrodes is limited by its prohibitively low diffusivity and solubility in water. Gas-diffusion electrodes (GDEs) can be used to reduce these limitations, and facilitate current densities orders of magnitude higher than the limiting current densities of planar electrodes. These improvements are accompanied by increased variation in the local environment within the cathode, with significant effect on Faradaic efficiency. By developing a simple and freely available analytical model of a cathodic catalyst layer configured for the production of CO, we investigate the relationships between electrode reaction kinetics, cell operation conditions, catholyte composition and cell performance. Analytical methods allow us to cover parameter ranges that are intractable for numerical and experimental studies. We validate our findings against experimental and numerical results and provide a derivation and implementation of the analytical model.","CO reduction; Electrolysis; Local pH","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:80f2e7e2-37dd-41af-8d5d-ce8d7a27f66a","http://resolver.tudelft.nl/uuid:80f2e7e2-37dd-41af-8d5d-ce8d7a27f66a","Real-time temperature measurement in stochastic rotation dynamics","Fan, R. (TU Delft Complex Fluid Processing); Zachariah, Githin T. (Student TU Delft); Padding, J.T. (TU Delft Complex Fluid Processing); Hartkamp, Remco (TU Delft Complex Fluid Processing)","","2021","Many physical and chemical processes involve energy change with rates that depend sensitively on local temperature. Important examples include heterogeneously catalyzed reactions and activated desorption. Because of the multiscale nature of such systems, it is desirable to connect the macroscopic world of continuous hydrodynamic and temperature fields to mesoscopic particle-based simulations with discrete particle events. In this work we show how to achieve real-time measurement of the local temperature in stochastic rotation dynamics (SRD), a mesoscale method particularly well suited for problems involving hydrodynamic flows with thermal fluctuations. We employ ensemble averaging to achieve local temperature measurement in dynamically changing environments. After validation by heat diffusion between two isothermal plates, heating of walls by a hot strip, and by temperature programed desorption, we apply the method to a case of a model flow reactor with temperature-sensitive heterogeneously catalyzed reactions on solid spherical catalysts. In this model, adsorption, chemical reactions, and desorption are explicitly tracked on the catalyst surface. This work opens the door for future projects where SRD is used to couple hydrodynamic flows and thermal fluctuations to solids with complex temperature-dependent surface mechanisms.","","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:bb218062-a9c8-4964-9222-d46c805d10a8","http://resolver.tudelft.nl/uuid:bb218062-a9c8-4964-9222-d46c805d10a8","Multiscale modelling of wall-to-bed heat transfer in fixed beds with non-spherical pellets: From particle-resolved CFD to pseudo-homogenous models","Mohammadzadeh Moghaddam, E. (TU Delft Large Scale Energy Storage; TU Delft Complex Fluid Processing); Foumeny, Esmail A.; Stankiewicz, A.I. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2021","We investigate forced convective heat transfer in packings of spheres, cylinders and Raschig rings, made of glass, steel and alumina, in relatively narrow tubes. A detailed comparison is made between resolved pellet-scale, azimuthally-averaged temperature profiles, and 2D-axially-dispersed pseudo-homogenous plug flow (2D-ADPF) predictions. The local temperature deviates significantly from azimuthally-averaged profiles, which in turn deviate from 2D-ADPF predictions. We show that the length dependency of effective heat transfer parameters is caused by thermal (non-)equilibrium between fluid and solid phases along the bed and not related to inadequate insulation of the calming section or the thermocouple's cross or an under-developed velocity and thermal field at the bed inlet. The influence of pellet shape and thermal conductivity and tube-to-pellet diameter ratio on ker and hw are assessed. We conclude that the models of Specchia/Baldi/Gianetto/Sicardi for all flow regimes and of Martin/Nilles for the turbulent regime are recommended for practical use for spherical particles.","Effective heat transfer parameters; Length dependency; Packing; Particle-resolved CFD Simulations; Raschig rings; Rigid Body Dynamics","en","journal article","","","","","","","","","","","Large Scale Energy Storage","","",""
"uuid:a505b373-c6c6-4b9e-80fc-4ab63c80e16c","http://resolver.tudelft.nl/uuid:a505b373-c6c6-4b9e-80fc-4ab63c80e16c","Performance of an internally cooled and heated desiccant-coated heat and mass exchanger: Effectiveness criteria and design methodology","Jagirdar, Mrinal (National University of Singapore); Lee, Poh Seng (National University of Singapore); Padding, J.T. (TU Delft Complex Fluid Processing)","","2021","Internally cooled and heated desiccant-coated heat and mass exchangers (ICHDHMX) driven by low-grade heat are very attractive owing to their energy-saving potential, especially for applications where substantial moisture removal (such as air-conditioning) is a necessity. In this paper, we derive equations for the performance of an ideal ICHDHMX, allowing us to define humidity-ratio effectiveness (εY) and relative-humidity effectiveness (εRH) such that their values approach 1 as the performance approaches that of an ideal ICHDHMX. Besides an equation-based approach, an easy-to-use psychrometric-chart based approach is presented to determine the performance of an ideal ICHDHMX. We invoke conservation principles to ascertain whether or not it is feasible to use the ICHDHMX for a given set of inlet conditions of air and water streams for dehumidification and regeneration. The dimensions of the ICHDHMX can be determined using this methodology, not even requiring knowledge of a tuning parameter unless a precise outlet specific humidity is required. Simulations are conducted for cases involving three incoming hot water temperatures (38, 44 and 50 °C) and several mixing ratios of room return air (25 °C at 0.011 kg/kg dry air) and outdoor air (32 °C at 0.02 kg/kg dry air), typical of warm and humid weather conditions. For all cases, the cool-water inlet is fixed at 30 °C. The results show that even when the dehumidification air-stream humidity is high, if the regeneration air-stream humidity is low (typical of room-exhaust air), the operation of an ICHDHMX is feasible using a low regeneration temperature of only 38 °C. When the regeneration temperature is 50 °C, the exchanger can operate under the complete range of humidity conditions tested. A cooling coefficient of performance up to 9.8 and effectiveness value up to 0.88 is realized, while the fluid power required is generally very low. These findings substantiate the case for commercial adoption of this technology for air-conditioning.","Air conditioning; Desiccant coated heat exchanger; Desiccant dehumidification; Fin tube heat exchanger; HVAC; Modeling","en","journal article","","","","","","Accepted Author Manuscript","","2023-02-02","","","Complex Fluid Processing","","",""
"uuid:e3a0baa9-03eb-4179-a473-b5949f3b9649","http://resolver.tudelft.nl/uuid:e3a0baa9-03eb-4179-a473-b5949f3b9649","Fluidization of elongated particles—Effect of multi-particle correlations for drag, lift, and torque in CFD-DEM","Mema, I. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2021","Having proper correlations for hydrodynamic forces is essential for successful CFD-DEM simulations of a fluidized bed. For spherical particles in a fluidized bed, efficient correlations for predicting the drag force, including the crowding effect caused by surrounding particles, are already available and well tested. However, for elongated particles, next to the drag force, the lift force, and hydrodynamic torque also gain importance. In this work, we apply recently developed multi-particle correlations for drag, lift and torque in CFD-DEM simulations of a fluidized bed with spherocylindrical particles of aspect ratio 4 and compare them to simulations with widely used single-particle correlations for elongated particles. Simulation results are compared with previous magnetic particle tracking experimental results. We show that multi-particle correlations improve the prediction of particle orientation and vertical velocity. We also show the importance of including hydrodynamic torque.","CFD-DEM; fluidized bed; hydrodynamic torque; lift force; multi-particle correlations; nonspherical particles","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:425a899e-40be-4789-8537-18dfa1063bd6","http://resolver.tudelft.nl/uuid:425a899e-40be-4789-8537-18dfa1063bd6","Accurate voidage prediction in fluidisation systems for full-scale drinking water pellet softening reactors using data driven models","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht; Queen Mary University of London); de Moel, P.J. (TU Delft Sanitary Engineering; Waternet; Omnisys); Padding, J.T. (TU Delft Complex Fluid Processing); Baars, E.T. (Waternet); El Hasadi, Yousef M.F. (TU Delft Complex Fluid Processing); Boek, E.S. (Queen Mary University of London); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2020","In full-scale drinking water production plants in the Netherlands, central softening is widely used for reasons related to public health, client comfort, and economic and environmental benefits. Almost 500 million cubic meters of water is softened annually through seeded crystallisation in fluidised bed reactors. The societal call for a circular economy has put pressure on this treatment process to become more sustainable. By optimising relevant process conditions, the consumption of chemicals can be reduced, and raw materials reused. Optimal process conditions are feasible if the specific crystallisation surface area in the fluidised bed is large enough to support the performance of the seeded crystallisation process. To determine the specific surface area, crucial variables including voidage and particle size must be known. Numerous models can be found in the literature to estimate the voidage in liquid-solid fluidisation processes. Many of these models are based on semi-empirical porous-media-based drag relations like Ergun or semi-empirical terminal-settling based models such as Richardson-Zaki and fitted for monodisperse, almost perfectly round particles. In this study, we present new voidage prediction models based on accurate data obtained from elaborate pilot plant experiments and non-linear symbolic regression methods. The models were compared with the most popular voidage prediction models using different statistical methods. An explicit model for voidage estimation based on the dimensionless Reynolds and Froude numbers is presented here that can be used for a wide range of particle sizes, fluid velocities and temperatures and that can therefore be directly used in water treatment processes such as drinking water pellet softening. The advantage of this model is that there is no need for applying numerical solutions; therefore, it can be explicitly implemented. The prediction errors for classical models from the literature lie between 2.7 % and 11.4 %. With our new model, the voidage prediction error is reduced to 1.9 %.","Drinking water treatment; Fluidised bed reactors; Full-scale water softening; Voidage prediction; Symbolic computation; Data driven modelling","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:d8aa8f1a-9990-4479-b5e5-3c9e2974c6bf","http://resolver.tudelft.nl/uuid:d8aa8f1a-9990-4479-b5e5-3c9e2974c6bf","Improvement of voidage prediction in liquid-solid fluidized beds by inclusion of the Froude number in effective drag relations","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht; Queen Mary University of London); Padding, J.T. (TU Delft Complex Fluid Processing); van Vugt, W.H. (Hogeschool Utrecht); de Moel, P.J. (TU Delft Sanitary Engineering; Omnisys); Baars, E.T. (Waternet); Boek, E.S. (Queen Mary University of London); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2020","A novel effective drag relation for liquid-solid fluidisation is proposed, suitable for application in full-scale installations. This is achieved by presenting new insights related to the influence of the temporal-spatial heterogeneity on the effective hydrodynamic drag for large fluidised systems. While heterogeneous flow behaviour can be predicted increasingly accurately in CFD simulations that explicitly model the heterogeneous solids distribution, for the operation of many large-scale applications it is infeasible to perform such computationally intensive simulations. Therefore, there is a clear need for full-scale drag relations that effectively take into account the heterogeneous behaviour and irregular spatial particle distributions. Our new drag relation is based on a large set of experiments, which shows that the degree of overall expansion is not only dependent on the ratio of laminar-turbulent flow, but also on the amount of homogenous versus heterogeneous flow, which is not included in current full-scale drag relations. To include the effect of heterogeneity, the standard drag relation, based on the Reynolds number, is extended with a specific type of Froude number. Because fully turbulent flow regimes are rare in applications of liquid-solid fluidisation, our focus is not on the turbulent flow regime but instead on laminar and transitional flow regimes. In these regimes, three types of models are investigated. The first type is based on a theoretical similarity with terminal settling, the second is based on the semi-empirical Carman-Kozeny model, and the third is based on empirical equations using symbolic regression techniques. For all three types of models, coefficients are calibrated on experimental data with monodisperse and almost spherical glass beads. The models are validated with a series of calcium carbonate grains applied in drinking water treatment processes as well as data obtained from the literature. Using these models, we show that the voidage prediction average relative error decreases from approximately 5% (according to the best literature equations which use Reynolds number only) to 1-2% (using both Reynolds and Froude number). This implies that our new models are more suitable for operational control in full-scale fluidised bed applications, such as pellet softening in drinking water treatment processes.","Accurate voidage prediction; Carman-Kozeny equation; Drag relations; Drinking water; Hydraulic models; Liquid-solid fluidisation","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:6f1d6e18-b9c1-4456-8c00-0aeea00e7301","http://resolver.tudelft.nl/uuid:6f1d6e18-b9c1-4456-8c00-0aeea00e7301","Fluidization of spherical versus elongated particles: Experimental investigation using magnetic particle tracking","Mema, I. (TU Delft Complex Fluid Processing); Buist, Kay A. (Eindhoven University of Technology); Kuipers, J. A.M. (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","In biomass processing fluidized beds are used to process granular materials where particles typically possess elongated shapes. However, for simplicity, in computer simulations particles are often considered spherical, even though elongated particles experience more complex particle–particle interactions as well as different hydrodynamic forces. The exact effect of these more complex interactions in dense fluidized suspensions is still not well understood. In this study we use the magnetic particle tracking technique to compare the fluidization behavior of spherical particles to that of elongated particles. We found a considerable difference between fluidization behavior of spherical versus elongated particles in the time-averaged particle velocity field as well as in the time-averaged particle rotational velocity profile. Moreover, we studied the effect of fluid velocity and the particle's aspect ratio on the particle's preferred orientation in different parts of the bed, which provides new insight in the fluidization behavior of elongated particles.","elongated particles; fluidization; particle orientation; particle velocity","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:afb0c907-234d-48b9-90b7-54d2a8d5e783","http://resolver.tudelft.nl/uuid:afb0c907-234d-48b9-90b7-54d2a8d5e783","Mixing of Viscoelastic Fluid Flows in a Coiled Flow Inverter","Vikrant, V. (TU Delft Complex Fluid Processing); Topalović, Anis (Student TU Delft); Monechi, Guido (Student TU Delft); Alsudani, Ali (Student TU Delft); Nigam, Krishna D.P. (Indian Institute of Technology Delhi); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","Despite having the advantage of a secondary flow pattern in coiled tubes, a very high Dean number is required to induce significant mixing in helical coils, usually implying high shear rates. At very high shear rates, polymer fluids with long molecular chains can be damaged. Therefore, in this study, we investigate the enhancement of mixing of a viscoelastic fluid in a coiled tube at low Dean numbers using the concept of a coiled flow inverter (CFI). Viscoelastic flow simulations were performed for CFIs of different curvature ratios, by changing the coil diameter, for a range of Weissenberg numbers (Wi) 0-125. An analytical method using velocity streamlines to quantify mixing is presented. The pressure drop per unit length increases with increasing Wi number. A more efficient mixing is predicted in the CFI, when compared with a helix of the same curvature ratio for all flow conditions. The mixing in the CFI is improved with an increase in flow rates (Wi). The mixing is enhanced at every bend because of flow inversion in the CFI.","","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:129999ee-8634-4c5d-b4ad-fd0bf064e1d1","http://resolver.tudelft.nl/uuid:129999ee-8634-4c5d-b4ad-fd0bf064e1d1","Hydrodynamics of narrow-tube fixed bed reactors filled with Raschig rings","Mohammadzadeh Moghaddam, E. (TU Delft Large Scale Energy Storage); Foumeny, E. A.; Stankiewicz, A.I. (TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","The local flow structure and pressure drop in random packings of Raschig rings are analyzed using sequential Rigid Body Dynamics (RBD) method and Computational Fluid Dynamics (CFD) simulation. Tube-to-pellet diameter ratios, N, between 3 and 6 are investigated for laminar, transitional and turbulent flow regimes (5 ≤ Rep ≤ 3,000). The computed pressure drops are in good agreement with the empirical correlation of Nemec and Levec (2005), while the Ergun equation exhibited high deviations of more than 60%, even when it is modified to explicitly account for non-sphericity of pellets. This deviation is ascribed to additional sources for eddy formation offered by Rashig rings, compared to spheres and cylinders, which cannot be counterbalanced by the usage of a higher specific surface area. The 3D results of flow structure demonstrate a large influence of packing topology on the velocity distribution: rings oriented parallel to the flow accelerate the local velocity through their axial holes, while rings oriented perpendicular to the flow provide additional space for vortex formation. The flow fields are substantially different from that found in packings of spheres and cylinders, both in terms of volume of backflow regions and velocity hotspots. This implies a higher order of local flow inhomogeneity in azimuthal and axial directions compared to spherical and cylindrical packings. Furthermore, it is found that azimuthal averaging of the 3D velocity field over the bed volume, which has been used to improve classical plug-flow pseudo-homogenous models to account for the role of tortuous velocity fields, cannot reflect the appearance of vortex regions and thereby leads to underestimation of the local axial velocity values by over 500% of the inlet velocity.","Azimuthal Averaging; Fixed Beds; Hydrodynamics; Particle – resolved CFD Simulations; Raschig rings; Rigid Body Dynamics","en","journal article","","","","","","","","","","","Large Scale Energy Storage","","",""
"uuid:5d21ef50-4130-4bc0-bfc2-177529b92aa7","http://resolver.tudelft.nl/uuid:5d21ef50-4130-4bc0-bfc2-177529b92aa7","Parallelization of a stochastic Euler-Lagrange model applied to large scale dense bubbly flows","Kamath, S. (Eindhoven University of Technology); Masterov, M. V. (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing); Buist, K. A. (Eindhoven University of Technology); Baltussen, M. W. (Eindhoven University of Technology); Kuipers, J. A.M. (Eindhoven University of Technology)","","2020","A parallel and scalable stochastic Direct Simulation Monte Carlo (DSMC) method applied to large-scale dense bubbly flows is reported in this paper. The DSMC method is applied to speed up the bubble-bubble collision handling relative to the Discrete Bubble Model proposed by Darmana et al. (2006) [1]. The DSMC algorithm has been modified and extended to account for bubble-bubble interactions arising due to uncorrelated and correlated bubble velocities. The algorithm is fully coupled with an in-house CFD code and parallelized using the MPI framework. The model is verified and validated on multiple cores with different test cases, ranging from impinging particle streams to laboratory-scale bubble columns. The parallel performance is shown using two different large scale systems: with an uniform and a non-uniform distribution of bubbles. The hydrodynamics of a pilot-scale bubble column is analyzed and the effect of the column scale is reported via the comparison of bubble columns at three different scales.","Bubble columns; Direct Simulation Monte Carlo; Euler-Lagrange modelling; Parallelization","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:bd92acf5-f956-4280-b4e1-1e0802d46d18","http://resolver.tudelft.nl/uuid:bd92acf5-f956-4280-b4e1-1e0802d46d18","Fluidization of spherical versus elongated particles - experimental investigation using X-ray tomography","Mema, I. (TU Delft Complex Fluid Processing); Wagner, E.C. (TU Delft ChemE/Afdelingsbureau); van Ommen, J.R. (TU Delft ChemE/Product and Process Engineering); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","In many industrial applications, particles used in fluidized bed clearly deviate from ideal spheres. This leads to an increasing need for better understanding and developing better simulation models for fluidization of non-spherical particles. So far, the literature is quite scarce when it comes to experimental results which can be used for validation of numerical models. Also, the exact difference in fluidization behavior between spherical and elongated particles in dense fluidizing conditions is not well understood. In this work, we apply X-ray tomography to compare the fluidization behavior of a bed of a Geldart D-type spherical particles of aspect ratio 4 to that of volume equivalent spherocylindrical particles for different gas velocities. Even though the beds of both spherical and elongated particles are operating in the slugging regime, due their size and high bed height to width ratio, we see clear differences in their fluidization behavior. Our results indicate that the bed of elongated particles is slugging less than the one with spherical particles. This is indicated by a lower average bubble size in the case of elongated particles, together with a higher bubble rise velocity. The bed of elongated particles has a considerably higher distribution of small and medium bubbles. The slug waiting time distribution and slug frequency distribution indicate that a bed of elongated particles periodically switches between slugging and turbulent fluidization, unlike the bed of spherical particles which remains in the constant slugging regime.","Elongated particles; Fluidization; Geldart D; Slugging; X-ray tomography","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:51ffbf8b-c27f-40d6-a030-0c4dc005ff24","http://resolver.tudelft.nl/uuid:51ffbf8b-c27f-40d6-a030-0c4dc005ff24","Hydrodynamic forces on monodisperse assemblies of axisymmetric elongated particles: Orientation and voidage effects","Pacha Sanjeevi, S.K. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","We investigate the average drag, lift, and torque on static assemblies of capsule-like particles of aspect ratio 4. The performed simulations are from Stokes flow to high Reynolds numbers (0.1 ≤ Re ≤ 1,000) at different solids volume fraction (0.1 ≤ ɛs ≤ 0.5). Individual particle forces as a function of the incident angle ϕ with respect to the average flow are scattered. However, the average particle force as a function of ϕ is found to be independent of mutual particle orientations for all but the highest volume fractions. On average, a sine-squared scaling of drag and sine-cosine scaling of lift holds for static multiparticle systems of elongated particles. For a packed bed, our findings can be utilized to compute the pressure drop with knowledge of the particle-orientation distribution, and the average particle drag at ϕ = 0° and 90°. We propose closures for average forces to be used in Euler–Lagrange simulations of particles of aspect ratio 4.","drag, lift, and torque correlations; nonspherical particles; particle assemblies","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:6d1c1ffd-7691-4805-855b-7b0c382f778e","http://resolver.tudelft.nl/uuid:6d1c1ffd-7691-4805-855b-7b0c382f778e","A novel approach to MP-PIC: Continuum particle model for dense particle flows in fluidized beds","Vikrant, V. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","A novel approach to Multiphase-Particle-in-Cell (MP-PIC), called Continuum Particle Model (CPM), is developed for dense gas-particle flows. CPM has high computational speed, comparable to that of MP-PIC, but a robustness and accuracy closer to that of a Discrete Element Model (DEM). The gas phase is treated as a continuum phase and particles are tracked discretely, but particle collisions are modelled by considering the divergence of the continuum particle stress tensor. Details on efficient solution to the model are presented. For comparison, a parametric study is performed for quasi-2D fluidized beds. Comparison of CFD-CPM is made with MP-PIC and CFD-DEM. The particle stress models by Harris and Crighton, and by Srivastava and Sundaresan are tested in our CFD-CPM. Results from CFD-CPM based on the Srivastava and Sundaresan particle stress model show good agreement with CFD-DEM results. We validate our model by comparison with experimental benchmark results from Gopalan et. al. (2016).","Coarse-grained simulations; Continuum Particle Model (CFD-CPM); Discrete Element Model (CFD-DEM); Fluidized beds; Multiphase Particle-in-cell (MP-PIC); Particle stresses","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:8f61a855-37c4-4872-becc-4f2410f86e24","http://resolver.tudelft.nl/uuid:8f61a855-37c4-4872-becc-4f2410f86e24","The effect of hydrodynamics on the crystal nucleation of nearly hard spheres","Fiorucci, Giulia (Universiteit Utrecht); Coli, Gabriele M. (Universiteit Utrecht); Padding, J.T. (TU Delft Complex Fluid Processing); Dijkstra, Marjolein (Universiteit Utrecht)","","2020","We investigate the effect of hydrodynamic interactions (HIs) on the crystal nucleation of hard-sphere colloids for varying supersaturations. We use molecular dynamics and stochastic rotation dynamics techniques to account for the HIs. For high supersaturation values, we perform brute force simulations and compute the nucleation rate, obtaining good agreement with previous studies where HIs were neglected. In order to access low supersaturation values, we use a seeding approach method and perform simulations with and without HIs. We compute the nucleation rates for the two cases and surprisingly find good agreement between them. The nucleation rate in both cases follows the trend of the previous numerical results, thereby corroborating the discrepancy between experiments and simulations. Furthermore, we investigate the amount of fivefold symmetric clusters (FSCs) in a supersaturated fluid under different physical conditions, following the idea that FSCs compete against nucleation. To this end, we explore the role of the softness of the pair interactions, different solvent viscosities, and different sedimentation rates in simulations that include HIs. We do not find significant variations in the amount of FSCs, which might reflect the irrelevance of these three features on the nucleation process.","","en","journal article","","","","","","","","2021-02-10","","","Complex Fluid Processing","","",""
"uuid:0943398c-aa91-43b2-b505-64ea44f57102","http://resolver.tudelft.nl/uuid:0943398c-aa91-43b2-b505-64ea44f57102","Spherical versus elongated particles – Numerical investigation of mixing characteristics in a gas fluidized bed","Mema, I. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2020","The possibility to offer good intermixing between particles is one of the main properties that make fluidized beds such an important industrial appliance. In this work, we use CFD-DEM simulations to compare mixing characteristics of spherical (AR-1) to elongated spherocylindrical particles (AR-4) of aspect ratio In simulation of AR-4 particles, single-particle and multi-particle correlations for hydrodynamic forces are tested. The results show that elongated particles have more vigorous intermixing and lower mixing times compared to spherical particles. Multi-particle correlations have a slight effect on particle mixing, and they increase the difference between AR-1 and AR-4 particles at higher gas velocities. Including hydrodynamic lift force and torque in the case of AR-4 particles leads to more vigorous mixing and lower mixing times.","CFD-DEM; Fluidized bed; Geldart D; Mixing; Non-spherical particles","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:149466cd-f81a-4e18-b98e-283c1ee10252","http://resolver.tudelft.nl/uuid:149466cd-f81a-4e18-b98e-283c1ee10252","Lift-off of multiple particles in a narrow channel","Maitri, R. V. (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing); Kuipers, J. A.M. (Eindhoven University of Technology); Peters, E. A.J.F. (Eindhoven University of Technology)","","2020","In this work, we perform simulations of particle laden flow in a wide and long narrow channel in a Newtonian fluid. Simulations are performed for mono-sized and equal density spheres with varying Archimedes and Reynolds number. In the simulations, different phases of particle transport - rolling, saltation and suspension are observed. During simulations the average bed height is monitored and its steady state value is used for proposing a correlation between solids volume fraction (ϕ), shear Reynolds number (Res) and Archimedes number (Ar). This correlation is used to predict the critical shear Reynolds number for particle lift-off and a condition at which particles would occupy the whole channel at a given Archimedes number. The value of this critical Reynolds number is compared with the critical Reynolds number for single particle lift-off.","Lift-off; Particle bed; Particle-resolved CFD; Sedimentation","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:3244311d-a89e-42b7-93bf-351f13560ec1","http://resolver.tudelft.nl/uuid:3244311d-a89e-42b7-93bf-351f13560ec1","Accurate prediction of liquid-solid fluidized bed porosity in drinking water treatment processes using empirical data-driven genetic programming models","Kramer, O.J.I. (TU Delft Complex Fluid Processing; Waternet; Hogeschool Utrecht); El Hasadi, Yousef M.F. (TU Delft Complex Fluid Processing); de Moel, P.J. (TU Delft Sanitary Engineering; Omnisys); Baars, Eric T. (Waternet); Padding, J.T. (TU Delft Complex Fluid Processing); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2019","For an accurate prediction of the porosity of a liquid-solid homogenous fluidized bed, various empirical prediction models have been developed. Symbolic regression machine learning techniques are suitable for analyzing experimental fluidization data to produce empirical expressions for porosity as a function not only of fluid velocity and viscosity but also of particle size and shape. On the basis of this porosity, it becomes possible to calculate the specific surface area for reactions for seeded crystallization in a fluidized bed.","liquid-solid fluidization; drinking water; porosity; hydraulic models; symbolic regression; genetic programming","en","conference paper","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:ded65596-6ec7-4cd8-afd8-c202bcae761c","http://resolver.tudelft.nl/uuid:ded65596-6ec7-4cd8-afd8-c202bcae761c","Preferential Adsorption in Mixed Electrolytes Confined by Charged Amorphous Silica","Döpke, M.F. (TU Delft Complex Fluid Processing); Lützenkirchen, Johannes (Karlsruhe Institut für Technologie); Moultos, O. (TU Delft Engineering Thermodynamics); Siboulet, Bertrand (Université de Montpellier); Dufrêche, Jean François (Université de Montpellier); Padding, J.T. (TU Delft Complex Fluid Processing); Hartkamp, Remco (TU Delft Complex Fluid Processing)","","2019","Preferential ion adsorption in mixed electrolytes plays a crucial role in many practical applications, such as ion sensing and separation and in colloid science. Using all-atom molecular dynamics simulations of aqueous NaCl, CaCl2, and NaCl-CaCl2 solutions confined by charged amorphous silica, we show that Na+ ions can adsorb preferentially over Ca2+ ions, depending on the surface structure. We propose that this occurs when the local surface structure sterically hinders the first hydration shell of the Ca2+ ion. Introducing a protrusion metric as a function of protrusion of deprotonated silanols, ion-specificity is successfully predicted on isolated, vicinal, and geminal silanols alike, provided that no other deprotonated silanols are found nearby. Furthermore, we introduce a new strategy to analyze the results as a function of distance from the surface. This approach effectively removes surface roughness effects allowing for direct comparison with classical electric double layer theory and distinction of specifically adsorbed ions and electrostatically adsorbed ions.","","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:127e55fa-61d8-46f7-8919-43025a53e256","http://resolver.tudelft.nl/uuid:127e55fa-61d8-46f7-8919-43025a53e256","Solving fluid flow problems using semi-supervised symbolic regression on sparse data","El Hasadi, Yousef M.F. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2019","The twenty first century is the century of data. Machine learning data and driven methods start to lead the way in many fields. In this contribution, we will show how symbolic regression machine learning methods, based on genetic programming, can be used to solve fluid flow problems. In particular, we will focus on the fluid drag experienced by ellipsoidal and spherocylinder particles of arbitrary aspect ratio. The machine learning algorithm is trained semisupervised by using a very limited amount of data for a specific single aspect ratio of 2.5 for ellipsoidal and 4 for spherocylindrical particles. The effect of the aspect ratio is informed to the algorithm through what we call previous knowledge, for example, known analytical solutions in certain limits, or through interbreeding of different flow solutions from the literature. Our results show good agreement with literature results, while they are obtained computationally faster and with less computing resources. Also, the machine learning algorithm discovered that for the case of prolate spheroids, the difference between the drag coefficients perpendicular and parallel to the flow in the high Reynolds number regime only depend on the aspect ratio of the geometry, even when the individual drag coefficients still decrease with increasing Re.","OA-Fund TU Delft","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:eb4603f1-67ba-4d91-b6d4-7ec0e0e9f56a","http://resolver.tudelft.nl/uuid:eb4603f1-67ba-4d91-b6d4-7ec0e0e9f56a","Droplet collisions of water and milk in a spray with Langevin turbulence dispersion","Finotello, Giulia (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems); Buist, Kay A. (Eindhoven University of Technology); Jongsma, Alfred (Tetra Pak CPS); Innings, Fredrik (Tetra Pak CPS); Kuipers, J. A.M. (Eindhoven University of Technology)","","2019","In this work we investigate droplet-droplet collision interactions in a spray system using an Eulerian-Lagrangian model with subgrid turbulence dispersion. The effect of different droplet viscosities on the type and frequency of droplet collision is investigated, knowledge of which is essential for industrial processes such as spray drying for production of milk powder. The dispersed phase is treated with Lagrangian transport of droplets and the turbulent self-induced gas flow using large eddy simulation (LES). A stochastic Direct Simulation Monte Carlo (DSMC) method is used to detect collisions between droplets. The outcome of a binary collision is described by a collision boundary models for water and milk concentrates. A turbulence dispersion model, based on the Langevin equation, accounts for the stochastic subgrid fluid velocity fluctuations along the droplet trajectory. We compare the spray dynamics with and without droplet interactions and turbulence dispersion. For a spray with typical droplet size of 50 µm, we find that the turbulence dispersion model enhances the total collision frequencies by approximately 25%. The performance of the turbulent dispersion model is tested by investigating the rate of collisions for different milk concentrates. The evolution of size distributions inside the spray is strongly influenced by the complementary effects of collision boundary models and turbulence dispersion.","Bouncing; Coalescence; Eulerian-Lagrangian model; Langevin subgridscale model; Separation","en","journal article","","","","","","Accepted Author Manuscript","","2021-03-15","","","Complex Fluid Processing","","",""
"uuid:14bbf799-b254-4024-a19f-9cb61f642253","http://resolver.tudelft.nl/uuid:14bbf799-b254-4024-a19f-9cb61f642253","Numerical investigation of droplet-droplet collisions in a water and milk spray with coupled heat and mass transfer","Finotello, Giulia (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing); Buist, Kay A. (Eindhoven University of Technology); Schijve, Annelien (Eindhoven University of Technology); Jongsma, Alfred (Tetra Pak CPS); Innings, Fredrik (Tetra Pak CPS); Kuipers, J.A.M. (Eindhoven University of Technology)","","2019","Large scale simulation models can aid in improving the design of spray dryers. In this work an Eulerian-Lagrangian model with coupled gas phase and droplet heat and mass transfer balances is used to study airflow dynamics, temperature and humidity profiles at different positions in the spray. The turbulent gas flow is solved using large eddy simulation (LES). A turbulent dispersion model accounts for the stochastic subgrid fluid velocity fluctuations along the droplet trajectory. The dispersed phase is treated with Lagrangian transport of droplets, and collisions between droplets which are detected with a stochastic Direct Simulation Monte Carlo (DSMC) method. The outcome of a binary collision is described by collision boundary models for water and milk concentrates. The drying of droplets is modeled by the reaction engineering approach (REA). The effect of the inlet air conditions and of droplet viscosity on the temperature and humidity distributions are analyzed. Most of the heat and mass transfer occurs in the first 10-20 cm from the nozzle where the slip velocities and temperature and humidity driving forces are higher. The droplets size increases, both in the axial and radial direction, because of the dominance of coalescence over separation in the droplet spray studied here. Because the spray domain considered in this work is relatively small, the droplet residence time is small, and consequently the amount of evaporation is still low. The droplet size distributions of milk concentrates are affected by the predominance of coalescence over separation events. The coalescence dominated regime increases when the droplet viscosity is higher.","droplet collisions; Eulerian-Lagrangian model; evaporation; heat and mass transfer; Spray drying","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:9fc4115b-5624-4a1b-a434-b71b53e62cce","http://resolver.tudelft.nl/uuid:9fc4115b-5624-4a1b-a434-b71b53e62cce","Improvement of the Richardson-Zaki liquid-solid fluidisation model on the basis of hydraulics","Kramer, O.J.I. (TU Delft Complex Fluid Processing; TU Delft Sanitary Engineering; Waternet; Hogeschool Utrecht); de Moel, P.J. (TU Delft Sanitary Engineering; Omnisys); Baars, E.T. (Waternet); van Vugt, W.H. (Hogeschool Utrecht); Padding, J.T. (TU Delft Complex Fluid Processing); van der Hoek, J.P. (TU Delft Sanitary Engineering; Waternet)","","2019","One of the most popular and frequently used models for describing homogeneous liquid-solid fluidised suspensions is the model developed by Richardson & Zaki in 1954. The superficial fluid velocity and terminal settling velocity together with an index makes it possible to determine the fluid porosity in a straightforward way. The reference point for the Richardson-Zaki model is the terminal settling velocity at maximum porosity conditions. To be able to predict porosity in the proximity of minimum fluidisation conditions, either the minimum fluidisation velocity must be known or the Richardson-Zaki index must be very accurate. To maintain optimal process and control conditions in multiphase drinking water treatment processes, the porosity is kept relatively low. Unfortunately, the Richardson-Zaki index models tends to overestimate the minimum fluidisation velocity and therefore also results in less accurate predictions with respect to porosity values. We extended the Richardson-Zaki model with proven hydraulics-based models. The minimum fluidisation velocity is acquired using the model proposed by Kozeny (1927), Ergun (1952) and Carman (1937). The terminal settling velocity is obtained through the model developed by Brown & Lawler (2003), which is an improved version of the well-known model developed by Schiller & Naumann (1933). The proposed models are compared with data from expansion experiments with calcium carbonate grains, crushed calcite and garnet grains applied in drinking water softening using the fluidised bed process. With respect to porosity, prediction accuracy is improved, with the average relative error decreasing from 15% to 3% when the classic Richardson-Zaki model is extended with these hydraulics-based models. With respect to minimum fluidisation velocity, the average relative error decreases from 100% to 12%. In addition, simplified analytical equations are given for a straightforward estimation of the index n.","Drinking water; Hydraulic models; Liquid-solid fluidisation; Minimal fluidisation; Richardson-Zaki; Terminal settling velocity","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:0e8edd8b-55cc-4b4e-a178-0d3bf09d0569","http://resolver.tudelft.nl/uuid:0e8edd8b-55cc-4b4e-a178-0d3bf09d0569","Effect of microchannel structure and fluid properties on non-inertial particle migration","Maitri, R. V. (Eindhoven University of Technology); De, S. (Eindhoven University of Technology; Shell); Koesen, S. P. (Eindhoven University of Technology); Wyss, H. M. (Eindhoven University of Technology); van der Schaaf, J. (Eindhoven University of Technology); Kuipers, J. A.M. (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems); Peters, E.A.J.F. (Eindhoven University of Technology)","","2019","In this work, we investigate the influence of channel structure and fluid rheology on non-inertial migration of non-Brownian polystyrene beads. Particle migration in this regime can be found in biomedical, chemical, environmental and geological applications. However, the effect of fluid rheology on particle migration in porous media remains to be clearly understood. Here, we isolate the effects of elasticity and shear thinning by comparing a Newtonian fluid, a purely elastic (Boger) fluid, and a shear-thinning elastic fluid. To mimic the complexity of geometries in real-world application, a random porous structure is created through a disordered arrangement of cylindrical pillars in the microchannel. Experiments are repeated in an empty channel and in channels with an ordered arrangement of pillars, and the similarities and differences in the observed particle focusing are analyzed. It is found that elasticity drives the particles away from the channel walls in an empty microchannel. Notably, particle focusing is unaffected by curved streamlines in an ordered porous microchannel and particles stay away from pillars in elastic fluids. Shear-thinning is found to reduce the effect of focusing and a broader region of particle concentration is observed. It is also noteworthy that the rheological characteristics of the fluid are not important for the particle distribution in a randomly arranged pillared microchannel and particles have a uniform distribution for all suspending fluids. Moreover, discussion on the current discrepancy in the literature about the equilibrium positions of the particles in a channel is extended by analyzing the results obtained in the current experiments.","","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:ad9c4ada-126c-4c5d-b2d5-b14024bf38af","http://resolver.tudelft.nl/uuid:ad9c4ada-126c-4c5d-b2d5-b14024bf38af","Fixed bed reactors of non-spherical pellets: Importance of heterogeneities and inadequacy of azimuthal averaging","Mohammadzadeh Moghaddam, E. (TU Delft Large Scale Energy Storage; TU Delft Intensified Reaction and Separation Systems); Foumeny, E. A. (Student TU Delft); Stankiewicz, A.I. (TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems)","","2019","Despite the substantial simplicities inherent in pseudo-continuum models of fixed bed reactors, there is a continued interest in the use of such models for predicting fluid flow and transport scalars. In this paper, we aim to quantitatively address the inadequacy of 2D pseudo-continuum models for narrow-tube fixed beds. We show this by comparing with spatially resolved 3D results obtained by a robust and integrated numerical workflow, consisting of a sequential Rigid Body Dynamics and Computational Fluid Dynamics (RBD-CFD) approach. The RBD is founded on a physics-based hard-body packing algorithm, recently proposed by the authors (Moghaddam, E.M., Foumeny, E.A., Stankiewicz, A.I., Padding, J.T., 2018. A Rigid Body Dynamics Algorithm for Modelling Random Packing Structures of Non-Spherical and Non-Convex Pellets. Ind. Eng. Chem. Res. 57, 14988–15007), which offers a rigorous method to handle resting contacts between particles. The methodology is benchmarked for simulations of flow fields in all flow regimes, for 5 ≤ Rep ≤ 3,000, in random packings of spheres and cylinders with tube-to-pellet diameter ratios, N, between 2.29 and 6.1. The CFD results reveal a remarkable influence of local structure on the velocity distribution at the pellet scale, particularly in low-N packings, where the spatial heterogeneity of the structure is very strong along the bed axis. It is also demonstrated that azimuthal averaging of the 3D velocity field over the bed volume, which has been considered as an advancement over plug flow idealization in classical pseudo-continuum models, cannot reflect the role of vortex regions emerging in the wake of the pellets, and leads to underestimation of the local velocity values by more than 400% of the inlet velocity.","Azimuthal averaging; Computational Fluid Dynamics; Fixed beds; Hydrodynamics; Non-spherical pellets; Rigid Body Dynamics","en","journal article","","","","","","","","","","","Large Scale Energy Storage","","",""
"uuid:2a812057-ec5e-4815-9176-bf4f0201aea6","http://resolver.tudelft.nl/uuid:2a812057-ec5e-4815-9176-bf4f0201aea6","Effect of lift force and hydrodynamic torque on fluidisation of non-spherical particles","Mema, I. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems); Mahajan, V.V. (TU Delft Intensified Reaction and Separation Systems; TU Delft Complex Fluid Processing); Fitzgerald, B. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems)","","2019","The aim of many industrial processes is to manipulate solid particle aggregates within gas suspensions. Prime examples of such processes include fluidised bed reactors, cyclone separators, and dust collectors. In recent years, fluidised bed reactors have been used in the gasification of biomass particles. When fluidised, these particles are subject to various hydrodynamic forces such as drag, lift and torque due to interactions with the fluid. Computational approaches, which can be used to replicate laboratory and industrial scale processes, offer a crucial method for the study of reactor design and for the formulation of optimal operating procedures. Until now, many computer models have assumed particles to be spherical whereas, in reality, biomass feedstocks typically consist of non-spherical particles. While lift and torque are of minimal importance for spherical particles, non-spherical particles experience varying lift force and torque conditions, depending on particle orientation relative to the direction of the fluid velocity. In this study, we present a numerical investigation on the effect of different lift force and torque correlations on fluidised spherocylindrical particles. We find that lift force has a significant influence on particle velocities parallel to the direction of gravity. On the other hand, particle orientation is dependent on hydrodynamic torque. Results from this numerical study provide new insight with regards to the dynamics of non-spherical particles that can be of paramount importance for industrial processes involving non-spherical particles.","CFD-DEM; Fluidised bed; Gas-solid flow; Hydrodynamic torque; Lift force; Non-spherical particles","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:08410afc-56ad-4319-ae3b-8a494f2ffa98","http://resolver.tudelft.nl/uuid:08410afc-56ad-4319-ae3b-8a494f2ffa98","Towards a particle based approach for multiscale modeling of heterogeneous catalytic reactors","Sengar, A. (Eindhoven University of Technology); Kuipers, J. A.M. (Eindhoven University of Technology); van Santen, R. A. (Eindhoven University of Technology); Padding, J.T. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems)","","2019","Particle based approaches are one of the recent modeling techniques to overcome the computational limitation in multiscale modeling of complex processes, for example a heterogeneous catalytic reactor. We propose an efficient model for a chemical reactor where hydrodynamics of the solvent is determined by Stochastic Rotation Dynamics and a reaction occurs over a catalytic surface where the reaction kinetics follows the mean-field assumption. We highlight the modeling techniques required to simulate such a system and then validate the model for its separate and combined components of convection, diffusion and reaction(s). A dimensionless analysis helps compare processes occurring at different scales. We determine the Reynolds number, Re, and the Damkohler numbers, Da and DaL in terms of key quantities. The approach is then used to analyse a reaction (a) following the Langmuir-Hinshelwood kinetics, (b) generating product particles with different self-diffusivity values as compared to the reactant particles. The model developed can further incorporate reactions occurring inside complex geometries (pore diffusion) and also be used to study complex reaction systems for which the mean-field assumption is no longer valid.","Heterogenous catalysis; Multicomponent diffusion; Multiscale modelling; Nonlinear reactions; Stochastic rotation dynamics; Unsteady state modelling","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:3be05530-37c9-42db-834b-d8575d277575","http://resolver.tudelft.nl/uuid:3be05530-37c9-42db-834b-d8575d277575","Small asymmetric Brownian objects self-align in nanofluidic channels","Fiorucci, Giulia (Universiteit Utrecht); Padding, J.T. (TU Delft Complex Fluid Processing); Dijkstra, Marjolein (Universiteit Utrecht)","","2019","Although the self-alignment of asymmetric macro-sized objects of a few tens of microns in size have been studied extensively in experiments and theory, access to much smaller length scales is still hindered by technical challenges. We combine molecular dynamics and stochastic rotation dynamics techniques to investigate the self-orientation phenomenon at different length scales, ranging from the micron to the nano scale by progressively increasing the relative strength of diffusion over convection. To this end, we model an asymmetric dumbbell particle in Hele-Shaw flow and explore a wide range of Péclet numbers (Pe) and different particle shapes, as characterized by the size ratio of the two dumbbell spheres (R). By independently varying these two parameters we analyse the process of self-orientation and characterize the alignment of the dumbbell with the direction of the fluid flow. We identify three different regimes of strong, weak and no alignment and we map out a state diagram in Pe versus R plane. Based on these results, we estimate dimensional length scales and flow rates for which these findings would be applicable in experiments. Finally, we find that the characteristic reorientation time of the dumbbell is a monotonically decreasing function of the dumbbell anisotropy.","","en","journal article","","","","","","Accepted Author Manuscript","","2019-12-17","","","Complex Fluid Processing","","",""
"uuid:709a58b8-ebd5-4c0b-87ba-7639f77212db","http://resolver.tudelft.nl/uuid:709a58b8-ebd5-4c0b-87ba-7639f77212db","Gas flow through static particle arrangements with a channel: Resolved simulations and analytic considerations","Vila, A. (BG88); Pacha Sanjeevi, S.K. (TU Delft Complex Fluid Processing; TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Complex Fluid Processing); Pirker, Stefan","","2019","Fractures of particle assemblies happen frequently in dense gas-solid systems leading to a notable heterogeneity in the particle configuration, especially in case of cohesive powders and non-spherical particle interlocking. In this work, we investigate the influence of such heterogeneities on the hydrodynamic drag by studying the idealized case of a random arrangement of spheres with a channel-like void region. More specifically, we introduce this heterogeneity to a homogeneous particle arrangement by shifting apart two bulk regions, such that a void channel divides particle bulk. Single-relaxation-time lattice Boltzmann simulations were performed to resolve fluid flow through such arrested particle configurations and calculate the corresponding gas-particle momentum exchange and pressure drop. The calculated drag forces acting on the solids for random sphere arrangement are in good agreement with previously reported results of Hill et al. (2001b), Tenneti et al. (2011), and Tang et al. (2015). However, the overall momentum exchange obtained for configurations containing a heterogeneity is significantly lower. Obviously, the channel allows for a by-passing of a considerable amount of the flow leading to a reduced overall pressure drop and thereby underestimating the minimum fluidization velocity in a fluidized bed. Based on these direct numerical simulations, we examine the overall pressure drop dependence on the characteristic length scale (i.e. width) of the channel-like heterogeneity L c , the superficial Reynolds number (30 ⩽ Re ⩽ 300), and the solid volume fraction in the dense (i.e. bulk) region (0.4 ⩽ϕ p ⩽ 0.55). The width of the channel is varied within the order of magnitude of particle diameter D p (1 ⩽L c /D p ⩽4.36), decreasing an overall solid volume fraction (0.25 ⩽ϕ⩽ 0.55). In addition to the numerical simulations, we derive (semi)-analytic correlations for the dense bulk region as well as for the channel. As the simulations range from laminar to transitional flow, providing a single pressure drop correlation is very challenging. Therefore, we estimate the channel pressure drop with the appropriate correlations selected according to calculated superficial Reynolds number. For laminar flow, we achieved a good agreement between a combined (i.e. bulk and channel) analytical prediction of overall pressure drop and our resolved numerical simulation. In the transitional regime, the pressure drop values are more difficult to predict, with the better agreement as we approach the turbulent regime. We believe that this work can act as a basis for the development of future drag laws accounting for channel-like sub-grid heterogeneities.","Analytic correlations; Channel in particle bed; Gas-particle flow; Heterogeneous particle arrangement; Lattice Boltzmann simulation; Pressure drop","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:e9b9a67e-cf34-4cb4-8912-c9ec40491a34","http://resolver.tudelft.nl/uuid:e9b9a67e-cf34-4cb4-8912-c9ec40491a34","Fluid medium effect on stresses in suspensions of high-inertia rod-like particles","Mahajan, V.V. (TU Delft Intensified Reaction and Separation Systems); Mehmood, J. (TU Delft Fluid Mechanics); El Hasadi, Yousef M.F. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2019","The rheology of suspensions of high-inertia (or granular) non-spherical particles characterized by high particle Stokes and Reynolds numbers is rarely investigated. In this study, we investigate the rheology of suspensions of inertial rod-like particles of aspect ratio 4 subjected to shear flow. In particular, the effect of fluid medium (air, water) against dry granular simulations on the developed stresses is assessed. CFD-DEM simulations are performed for a periodic shear box for a range of shear rates and volume fractions of particles. The dependence of rheological properties like shear stress, normal stress difference, pressure and relative viscosity on volume fraction, shear rate, granular temperature and the particle orientation are discussed. These results provide insight into the macroscopic rheology of suspensions of rods and demonstrate that the effect of particle shape and surrounding fluid cannot be completely ignored. Air as a fluid medium shows similar scaling as compared to dry granular simulations, but the stress values are generally lower. We observe drastic change in both scaling and values for water as fluid medium. In all cases, the rods show strong alignment in the direction of shear. This study can be further extended to develop stress closures for use in Eulerian flow models.","CFD-DEM; Granular; Non-spherical; Rheology; Stress; Suspension","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:1bd9503d-00f2-4aca-8e0b-596e4986b468","http://resolver.tudelft.nl/uuid:1bd9503d-00f2-4aca-8e0b-596e4986b468","Multiscale simulation of elongated particles in fluidised beds","Fitzgerald, B. (TU Delft Complex Fluid Processing); Zarghami, A. (TU Delft Intensified Reaction and Separation Systems); Mahajan, V.V. (TU Delft Complex Fluid Processing); Pacha Sanjeevi, S.K. (TU Delft Complex Fluid Processing); Mema, I. (TU Delft Complex Fluid Processing); Vikrant, V. (TU Delft Complex Fluid Processing); El Hasadi, Yousef M.F. (TU Delft Complex Fluid Processing); Padding, J.T. (TU Delft Complex Fluid Processing)","","2019","In this paper, we present a number of key numerical methods that can be used to study elongated particles in fluid flows, with a specific emphasis on fluidised beds. Fluidised beds are frequently used for the production of biofuels, bioenergy, and other products from biomass particles, which often have an approximate elongated shape. This raises numerous issues in a numerical approach such as particle-particle contact detection and the accurate description of the various hydrodynamic forces, such as drag, lift, and torque, that elongated particles experience when moving in a fluid flow. The modelling is further complicated by a separation of length scales where industrial flow structures that can extend for many metres evolve subject to solid-solid and solid-fluid interactions at the millimetre scale. As a result, it is impossible to simulate both length scales using the same numerical approach, and a multiscale approach is necessary. First, we outline the direct numerical simulation (DNS) approach that may be employed to estimate hydrodynamic force closures for elongated particles in a fluid flow. We then describe the key aspects of a CFD-DEM approach, which can be used to simulate laboratory scale fluidisation processes, that must be addressed to study elongated particles. Finally, we briefly consider how current industrial-scale models, which concretely assume particle sphericity, could be adapted for the simulation of large collections of elongated particles subject to fluidisation.","CFD-DEM; Coarse-grained simulations; Discrete numerical simulations (DNS); Elongated particles; Fluidised beds; Multiscale simulations","en","journal article","","","","","","","","","","","Complex Fluid Processing","","",""
"uuid:45f8e12e-5d80-446d-9a97-7cac403fe1b1","http://resolver.tudelft.nl/uuid:45f8e12e-5d80-446d-9a97-7cac403fe1b1","Deactivation kinetics of solid acid catalyst with laterally interacting protons","Sengar, A. (Eindhoven University of Technology); Van Santen, Rutger A. (Eindhoven University of Technology); Steur, E. (TU Delft Team Bart De Schutter; Eindhoven University of Technology); Kuipers, J.A.M. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2018","","alkylation catalysis; solid acid catalysis; catalyst deactivation; laterally interacting protons; kinetics simulations; nonlinear dynamics; site percolation","en","journal article","","","","","","","","","","","Team Bart De Schutter","","",""
"uuid:e932137a-5be9-4a46-b29e-408bbd329384","http://resolver.tudelft.nl/uuid:e932137a-5be9-4a46-b29e-408bbd329384","An improved ghost-cell sharp interface immersed boundary method with direct forcing for particle laden flows","Maitri, R.V. (Eindhoven University of Technology); Das, S. (Eindhoven University of Technology); Kuipers, J.A.M. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology); Peters, E.A.J.F. (Eindhoven University of Technology)","","2018","In this paper, an accurate and stable sharp interface immersed boundary method(IBM) is presented for the direct numerical simulation of particle laden flows. The current IBM method is based on the direct-forcing method by incorporating the ghost-cell approach implicitly. An important feature of this IBM is the sharp representation of the solid surface, contrary to other variants of IBM for freely moving particles in which the solid surface is diffuse. Moreover, a correction of the diameter is not necessary for obtaining accurate results. The current ghost-cell IBM is stable because spurious oscillations incurred due to discontinuity in the pressure and velocity field in moving particle simulations is avoided. An algorithm for accurate torque computation is developed. The proposed algorithm is verified by comparison to an analytical expression and is shown to give a substantial improvement over the existing method. Finally, the present IBM is validated for various test cases of single and multi-particle systems and is shown to be accurate and robust for a wide range of flow conditions.","Immersed boundary method; Ghost cell approach; Particle laden flow; Projected area; Torque computation; Spurious oscillations","en","journal article","","","","","","Accepted Author Manuscript","","2020-10-16","","","Intensified Reaction and Separation Systems","","",""
"uuid:986dbaea-16cd-42b0-9056-f6d1c91fb7a0","http://resolver.tudelft.nl/uuid:986dbaea-16cd-42b0-9056-f6d1c91fb7a0","Flow of viscoelastic surfactants through porous media","De, S. (Eindhoven University of Technology); Koesen, S. P. (Eindhoven University of Technology); Maitri, R. V. (Eindhoven University of Technology); Golombok, M. (Eindhoven University of Technology; Shell Global Solutions International B.V.); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); van Santvoort, J. F.M. (Eindhoven University of Technology)","","2018","We compare the flow behavior of viscoelastic surfactant (VES) solutions and Newtonian fluids through two different model porous media having similar permeability: (a) a 3D random packed bed and (b) a microchannel with a periodically spaced pillars. The former provides much larger flow resistance at the same apparent shear rate compared to the latter. The flow profile in the 3D packed bed cannot be observed since it is a closed system. However, visualization of the flow profile in the microchannel shows strong spatial and temporal flow instabilities in VES fluids appear above a critical shear rate. The onset of such elastic instabilities correlates to the flow rate where increased flow resistance is observed. The elastic instabilities are attributed to the formation of transient shear induced structures. The experiments provide a detailed insight into the complex interplay between the pore scale geometry and rheology of VES in the creeping flow regime.","complex fluids; fluid mechanics; porous media; rheology","en","journal article","","","","","","","","2019-01-03","","","Intensified Reaction and Separation Systems","","",""
"uuid:ca047929-7eeb-4014-80c9-607a84e7c56d","http://resolver.tudelft.nl/uuid:ca047929-7eeb-4014-80c9-607a84e7c56d","Experimental investigation of non-Newtonian droplet collisions: the role of extensional viscosity","Finotello, Giulia (Eindhoven University of Technology); De, Shauvik (Eindhoven University of Technology); Vrouwenvelder, Jeroen C.R. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Buist, Kay A. (Eindhoven University of Technology); Jongsma, Alfred (Tetra Pak CPS); Innings, Fredrik (Tetra Pak CPS); Kuipers, J. A.M. (Eindhoven University of Technology)","","2018","We investigate the collision behaviour of a shear thinning non-Newtonian fluid xanthan, by binary droplet collision experiments. Droplet collisions of non-Newtonian fluids are more complex than their Newtonian counterpart as the viscosity no longer remains constant during the collision process. Despite the complex collision dynamics, we are able to present a complete regime map based on non-dimensional Weber (We) number and impact parameter (B). We compare the collision outcomes of xanthan, glycerol and a milk concentrate at similar impact conditions. These experiments reveal very rich and complex collision morphologies for shear thinning xanthan solution, strikingly different from Newtonian droplet collisions. Unlike glycerol and milk, xanthan collisions show no reflexive separation even at very high We number. Instead of breakup, we observe disc-like shapes with an oscillating behaviour of the colliding droplets. A detailed analysis reveals that this outcome is related to increased viscous energy dissipation and extensional effects.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:b909c373-b9a5-4fa2-adc4-c3e26b244094","http://resolver.tudelft.nl/uuid:b909c373-b9a5-4fa2-adc4-c3e26b244094","Rigid Body Dynamics algorithm for modeling random packing structures of nonspherical and nonconvex pellets","Mohammadzadeh Moghaddam, E. (TU Delft Intensified Reaction and Separation Systems); Foumeny, Esmail A.; Stankiewicz, A.I. (TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2018","Despite the common use of nonspherical catalyst pellets in chemical engineering applications, the packing structures of such pellets have not been as systematically studied and characterized as spherical packings. We propose a packing algorithm based on rigid body dynamics to simulate packing of nonspherical and possibly nonconvex pellets. The algorithm exerts a hard-body approach to model collision phenomena. The novelty is that the transition between moving and resting particles is controlled by a cutoff on the relative contact velocities, instead of artificially damping linear and angular velocities to stabilize the algorithm. The algorithm is used to synthesize packings of spheres, cylinders, and Raschig rings with tube-to-pellet diameter ratios 3-9.16. The packings are validated in terms of bulk porosity and radial void fraction distribution, finding satisfactory agreement with literature data. Denser packing structures are generated with high restitution coefficients and low friction coefficients. The confining tube walls play an important role, with highly fluctuating bulk porosities in narrow tubes.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:db8a52d4-321c-4b4c-839e-2fcf81f24add","http://resolver.tudelft.nl/uuid:db8a52d4-321c-4b4c-839e-2fcf81f24add","The dynamics of milk droplet–droplet collisions","Finotello, Giulia (Eindhoven University of Technology); Kooiman, Roeland F. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Buist, Kay A. (Eindhoven University of Technology); Jongsma, Alfred (Tetra Pak CPS); Innings, Fredrik (Tetra Pak CPS); Kuipers, J. A.M. (Eindhoven University of Technology)","","2018","Spray drying is an important industrial process to produce powdered milk, in which concentrated milk is atomized into small droplets and dried with hot gas. The characteristics of the produced milk powder are largely affected by agglomeration, combination of dry and partially dry particles, which in turn depends on the outcome of a collision between droplets. The high total solids (TS) content and the presence of milk proteins cause a relatively high viscosity of the fed milk concentrates, which is expected to largely influence the collision outcomes of drops inside the spray. It is therefore of paramount importance to predict and control the outcomes of binary droplet collisions. Only a few studies report on droplet collisions of high viscous liquids and no work is available on droplet collisions of milk concentrates. The current study therefore aims to obtain insight into the effect of viscosity on the outcome of binary collisions between droplets of milk concentrates. To cover a wide range of viscosity values, three milk concentrates (20, 30 and 46 % TS content) are investigated. An experimental set-up is used to generate two colliding droplet streams with consistent droplet size and spacing. A high-speed camera is used to record the trajectories of the droplets. The recordings are processed by Droplet Image Analysis in MATLAB to determine the relative velocities and the impact geometries for each individual collision. The collision outcomes are presented in a regime map dependent on the dimensionless impact parameter and Weber (We) number. The Ohnesorge (Oh) number is introduced to describe the effect of viscosity from one liquid to another and is maintained constant for each regime map by using a constant droplet diameter (d∼700μm). In this work, a phenomenological model is proposed to describe the boundaries demarcating the coalescence-separation regimes. The collision dynamics and outcome of milk concentrates are compared with aqueous glycerol solutions experiments. While milk concentrates have complex chemical composition and rheology, glycerol solutions are Newtonian fluids and therefore easy to characterize. The collision morphologies of glycerol solutions and milk concentrates are similar, and the regime maps can be described by the same phenomenological model developed in this work. The regime of bouncing, however, was not observed for any of the milk concentrates.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:845fcd26-269d-4e69-9e03-e7cdab733dc0","http://resolver.tudelft.nl/uuid:845fcd26-269d-4e69-9e03-e7cdab733dc0","Choice of no-slip curved boundary condition for lattice Boltzmann simulations of high-Reynolds-number flows","Pacha Sanjeevi, S.K. (TU Delft Intensified Reaction and Separation Systems); Zarghami, A. (TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2018","Various curved no-slip boundary conditions available in literature improve the accuracy of lattice Boltzmann simulations compared to the traditional staircase approximation of curved geometries. Usually, the required unknown distribution functions emerging from the solid nodes are computed based on the known distribution functions using interpolation or extrapolation schemes. On using such curved boundary schemes, there will be mass loss or gain at each time step during the simulations, especially apparent at high Reynolds numbers, which is called mass leakage. Such an issue becomes severe in periodic flows, where the mass leakage accumulation would affect the computed flow fields over time. In this paper, we examine mass leakage of the most well-known curved boundary treatments for high-Reynolds-number flows. Apart from the existing schemes, we also test different forced mass conservation schemes and a constant density scheme. The capability of each scheme is investigated and, finally, recommendations for choosing a proper boundary condition scheme are given for stable and accurate simulations.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:13ad8334-b6f8-48cd-a4d7-ca608e8f669e","http://resolver.tudelft.nl/uuid:13ad8334-b6f8-48cd-a4d7-ca608e8f669e","Nonspherical particles in a pseudo-2D fluidized bed: Experimental study","Mahajan, V.V. (TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Nijssen, Tim M.J. (Eindhoven University of Technology); Buist, Kay A. (Eindhoven University of Technology); Kuipers, J.R. (Eindhoven University of Technology)","","2018","Fluidization is widely used in industries and has been extensively studied, both experimentally and theoretically, in the past. However, most of these studies focus on spherical particles while in practice granules are rarely spherical. Particle shape can have a significant effect on fluidization characteristics. It is therefore important to study the effect of particle shape on fluidization behavior in detail. In this study, experiments in pseudo-2D fluidized beds are used to characterize the fluidization of spherocylindrical (rod-like) Geldart D particles of aspect ratio 4. Pressure drop and optical measurement methods (Digital Image Analysis, Particle Image Velocimetry, Particle Tracking Velocimetry) are employed to measure bed height, particle orientation, particle circulation, stacking, and coordination number. The commonly used correlations to determine the pressure drop across a bed of nonspherical particles are compared to experiments. Experimental observations and measurements have shown that rod-like particles are prone to interlocking and channeling behavior. Well above the minimum fluidization velocity, vigorous bubbling fluidization is observed, with groups of interlocked particles moving upwards, breaking up, being thrown high in the freeboard region and slowly raining down as dispersed phase. At high flowrates, a circulation pattern develops with particles moving up through the center and down at the walls. Particles tend to orient themselves along the flow direction.","bed height; Digital Image Analysis; fluidization; nonspherical; orientation; Particle Image Velocimetry; Particle Tracking Velocimetry; pressure drop","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:522058e8-eaf2-4e81-b9f6-2780498b6847","http://resolver.tudelft.nl/uuid:522058e8-eaf2-4e81-b9f6-2780498b6847","Stochastic DSMC method for dense bubbly flows: Methodology","Kamath, S. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Buist, K. A. (Eindhoven University of Technology); Kuipers, J.R. (Eindhoven University of Technology)","","2018","A stochastic Direct Simulation Monte Carlo (DSMC) method has been extended for handling bubble-bubble and bubble-wall collisions. Bubbly flows are generally characterized by highly correlated velocities due to presence of the surrounding liquid. The DSMC method has been improved to account for these kind of correlated collisions along with a treatment allowing the method to be used also at relatively high volume fractions. The method is first verified with the deterministic Discrete Particle/Bubble Model (DPM/DBM) using two problem cases: (a) dry granular flow of particles through two impinging nozzles and (b) 3D periodic bubble rise for mono-disperse and poly-disperse systems. The verification parameters are the total number of prevailing collisions within the system, the collision frequencies and the time-averaged liquid velocity profiles (only for the 3D-periodic bubble rise). Subsequently the method is applied to a lab-scale bubble column and validated with the experimental data of Deen et al. (2001). A computational performance comparison with the DBM is reported for the 3D periodic bubble rise case with varying overall gas fractions. The DSMC is approximately two orders of magnitude faster than the deterministic approach for the studied dense bubbly flow cases without adverse effects on the quality of the computational results.","Bubbly flow; Computational performance; Direct Simulation Monte Carlo; Discrete Bubble Model; Experimental validation","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:93d65ae9-9044-41b0-a541-865d4933b40e","http://resolver.tudelft.nl/uuid:93d65ae9-9044-41b0-a541-865d4933b40e","Drag, lift and torque correlations for non-spherical particles from Stokes limit to high Reynolds numbers","Pacha Sanjeevi, S.K. (TU Delft Intensified Reaction and Separation Systems); Kuipers, J. A.M. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2018","Accurate direct numerical simulations are performed to determine the drag, lift and torque coefficients of non-spherical particles. The numerical simulations are performed using the lattice Boltzmann method with multi-relaxation time. The motivation for this work is the need for accurate drag, lift and torque correlations for high Re regimes, which are encountered in Euler-Lagrangian simulations of fluidization and pneumatic conveying of larger non-spherical particles. The simulations are performed in the Reynolds number range 0.1 ≤ Re ≤ 2000 for different incident angles ϕ. Different tests are performed to analyse the influence of grid resolution and confinement effects for different Re. The measured drag, lift and torque coefficients are utilized to derive accurate correlations for specific non-spherical particle shapes, which can be used in unresolved simulations. The functional forms for the correlations are chosen to agree with the expected physics at Stokes flow as well as the observed leveling off of the drag coefficient at high Re flows. Therefore the fits can be extended to regimes outside the Re regimes simulated. We observe sine-squared scaling of the drag coefficient for the particles tested even at Re=2000 with CD,ϕ=CD,ϕ=0∘ +(CD,ϕ=90∘ −CD,ϕ=0∘ )sin2ϕ. Furthermore, we also observe that the lift coefficient approximately scales as CL,ϕ=(CD,ϕ=90∘ −CD,ϕ=0∘ )sinϕcosϕ for the elongated particles. The current work would greatly improve the accuracy of Euler-Lagrangian simulations of larger non-spherical particles considering the existing literature is mainly limited to steady flow regimes and lower Re.","Force and torque correlation; Lattice Boltzmann method; Non-spherical particles","en","journal article","","","","","","Accepted author manuscript","","2020-08-13","","","Intensified Reaction and Separation Systems","","",""
"uuid:7bd5d115-e66a-4e60-b1af-dfa2f083bbc5","http://resolver.tudelft.nl/uuid:7bd5d115-e66a-4e60-b1af-dfa2f083bbc5","Viscoelastic effects on residual oil distribution in flows through pillared microchannels","De, S. (Eindhoven University of Technology); Krishnan, P. (Eindhoven University of Technology); van der Schaaf, J. (Eindhoven University of Technology); Kuipers, J. A.M. (Eindhoven University of Technology); Peters, E. A.J.F. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2018","Hypothesis Multiphase flow through porous media is important in a number of industrial, natural and biological processes. One application is enhanced oil recovery (EOR), where a resident oil phase is displaced by a Newtonian or polymeric fluid. In EOR, the two-phase immiscible displacement through heterogonous porous media is usually governed by competing viscous and capillary forces, expressed through a Capillary number Ca, and viscosity ratio of the displacing and displaced fluid. However, when viscoelastic displacement fluids are used, elastic forces in the displacement fluid also become significant. It is hypothesized that elastic instabilities are responsible for enhanced oil recovery through an elastic microsweep mechanism. Experiments In this work, we use a simplified geometry in the form of a pillared microchannel. We analyze the trapped residual oil size distribution after displacement by a Newtonian fluid, a nearly inelastic shear thinning fluid, and viscoelastic polymers and surfactant solutions. Findings We find that viscoelastic polymers and surfactant solutions can displace more oil compared to Newtonian fluids and nearly inelastic shear thinning polymers at similar Ca numbers. Beyond a critical Ca number, the size of residual oil blobs decreases significantly for viscoelastic fluids. This critical Ca number directly corresponds to flow rates where elastic instabilities occur in single phase flow, suggesting a close link between enhancement of oil recovery and appearance of elastic instabilities.","Displacement fluid; Enhanced oil recovery; Oil droplet size distribution; Viscoelastic instability","en","journal article","","","","","","","","2019-09-23","","","Intensified Reaction and Separation Systems","","",""
"uuid:ae03c50e-bd93-46b5-9212-0e307ee2b702","http://resolver.tudelft.nl/uuid:ae03c50e-bd93-46b5-9212-0e307ee2b702","Experimental study on orientation and de-mixing phenomena of elongated particles in gas-fluidized beds","Boer, L. (Eindhoven University of Technology); Buist, K. A. (Eindhoven University of Technology); Deen, N. G. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Kuipers, J. A.M. (Eindhoven University of Technology)","","2018","In this experimental study the segregation behavior for fluidized mixtures of spherical and cylindrical particles is investigated. In industry, fluidization of particles featuring a wide range of shapes is common in various applications such as biomass gasification, drying applications, food processing and production of pharmaceuticals. Earlier publications have mainly focused on segregation of spherical particles of different volume or density. The particles used in this study have equal volume and density but a different shape. The main purpose of this work is to study de-mixing driven by particle shape. To analyze the particle distributions inside the fluidized bed, a Digital Image Analysis (DIA) technique has been developed, capable of capturing the particle positions and orientations within the bed over time. The experiments show that in the non-bubbling flow regime (at low fluidization velocities) rod-shaped particles may segregate, sinking to the bottom of the bed. In the bubbling flow regime (at higher fluidization velocities) segregation does not occur, because of bubble-induced mixing. Here strong alignment of the cylindrical particle's long axis with the flow is observed. The experimental results obtained give qualitative and quantitative insight in the behavior of non-spherical particles in fluidized beds and can be used for validation of numerical models concerning non-spherical particle mixing.","Fluidization; Fluidized beds; Granular dynamics; Mixing; Particle shape; Segregation","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:0bab1ae6-4b41-41b1-ae52-afcfba13db0d","http://resolver.tudelft.nl/uuid:0bab1ae6-4b41-41b1-ae52-afcfba13db0d","Non-spherical particles in a pseudo-2D fluidised bed: Modelling study","Mahajan, V.V. (TU Delft Intensified Reaction and Separation Systems); Nijssen, Tim M.J. (Eindhoven University of Technology); Kuipers, J.R. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2018","Fluidised beds are used in a variety of processes because of their favourable mass and heat transfer characteristics. In this and many other processes, non-spherical particles are commonplace, which can drastically affect the fluidisation behaviour. In this study, we use numerical models to study non-spherical fluidisation behaviour in detail. A crucial step in the development of the numerical model is a detailed validation with experimental data. The validated model can then be used with confidence for further investigations. In this study, the results obtained from CFD-DEM modelling are compared with detailed experiments (Mahajan et al., 2017). The particles used are of spherocylindrical shape with an aspect ratio 4. We discuss the numerical modelling strategy including the DEM contact detection algorithm and accurate voidage calculation algorithm. The non-spherical single particle drag model of Hölzer and Sommerfeld (2008) is compared with a DNS drag model for spherocylindrical particles developed in-house. We propose two new voidage correction models and compare results with the (Di Felice, 1994) model. The pressure drop, bed height, particle orientation, particle circulation, stacking of particles and coordination number obtained from simulations are compared with experiments. The numerical measurements show good agreement with experiments. Similar to experiments, simulations show that rod-like particles are prone to interlocking behaviour. At high gas flow rates above the minimum fluidisation velocity, vigorously bubbling fluidisation is observed, with gas bubbles moving up through the center and particles moving down at the side walls. The orientation of particles in the fluidised state do not match with the experiments when hydrodynamic torque is neglected. The importance of hydrodynamic torque and multi-particle drag in CFD-DEM modelling of non-spherical particles is demonstrated through these results.","Bed height; CFD-DEM; Coordination number; Experiments; Fluidisation; Non-spherical; Orientation; Pressure drop; Validation","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:5c1f3e2d-604f-49f5-9ab2-442bf9c9baf1","http://resolver.tudelft.nl/uuid:5c1f3e2d-604f-49f5-9ab2-442bf9c9baf1","A granular Discrete Element Method for arbitrary convex particle shapes: Method and packing generation","Seelen, L. J.H. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Kuipers, J.R. (Eindhoven University of Technology)","","2018","A novel granular discrete element method (DEM) is introduced to simulate mixtures of particles of any convex shape. To quickly identify pairs of particles in contact, the method first uses a broad-phase and a narrow-phase contact detection strategy. After this, a contact resolution phase finds the contact normal and penetration depth. A new algorithm is introduced to effectively locate the contact point in the geometric center of flat faces in partial contact. This is important for a correct evaluation of the torque on each particle, leading to a much higher stability of stacks of particles than with previous algorithms. The granular DEM is used to generate random packings in a cylindrical vessel. The simulated shapes include non-spherical particles with different aspect ratio cuboids, cylinders and ellipsoids. More complex polyhedral shapes representing sand and woodchip particles are also used. The latter particles all have a unique shape and size, resembling real granular particle packings. All packings are analyzed extensively by investigating positional and orientational ordering.","Contact detection; Discrete element method; Non-spherical particle; Orientational ordering; Packing; Solid volume fraction","en","journal article","","","","","","Accepted Author Manuscript","","2020-05-30","","","Intensified Reaction and Separation Systems","","",""
"uuid:ae34984f-0c44-4958-945b-9b4b42bd909f","http://resolver.tudelft.nl/uuid:ae34984f-0c44-4958-945b-9b4b42bd909f","On the orientational dependence of drag experienced by spheroids","Pacha Sanjeevi, S.K. (TU Delft Intensified Reaction and Separation Systems); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology)","","2017","The flow around different prolate (needle-like) and oblate (disc-like) spheroids is studied using a multi-relaxation-time lattice Boltzmann method. We compute the mean drag coefficient CD,ϕ at different incident angles ϕ for a wide range of Reynolds numbers ( Re ). We show that the sine-squared drag law CD,ϕ=CD,ϕ=0∘+(CD,ϕ=90∘−CD,ϕ=0∘)sin2ϕ holds up to large Reynolds numbers, Re=2000 . Further, we explore the physical origin behind the sine-squared law, and reveal that, surprisingly, this does not occur due to linearity of flow fields. Instead, it occurs due to an interesting pattern of pressure distribution contributing to the drag at higher Re for different incident angles. The present results demonstrate that it is possible to perform just two simulations at ϕ=0∘ and ϕ=90∘ for a given Re and obtain particle-shape-specific CD at arbitrary incident angles. However, the model has limited applicability to flatter oblate spheroids, which do not exhibit the sine-squared interpolation, even for Re=100 , due to stronger wake-induced drag. Regarding lift coefficients, we find that the equivalent theoretical equation can provide a reasonable approximation, even at high Re , for prolate spheroids.","multiphase and particle-laden flows; particle/fluid flow","en","journal article","","","","","","Accepted Author Manuscript","","2017-11-02","","","Intensified Reaction and Separation Systems","","",""
"uuid:1ce713a9-741b-4137-956b-c2ff4e8a396b","http://resolver.tudelft.nl/uuid:1ce713a9-741b-4137-956b-c2ff4e8a396b","Effect of viscosity on droplet-droplet collisional interaction","Finotello, Giulia (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Deen, Niels G. (Eindhoven University of Technology); Jongsma, Alfred (Tetra Pak CPS); Innings, Fredrik (Tetra Pak CPS); Kuipers, J.A.M. (Eindhoven University of Technology)","","2017","A complete knowledge of the effect of droplet viscosity on droplet-droplet collision outcomes is essential for industrial processes such as spray drying. When droplets with dispersed solids are dried, the apparent viscosity of the dispersed phase increases by many orders of magnitude, which drastically changes the outcome of a droplet-droplet collision. However, the effect of viscosity on the droplet collision regime boundaries demarcating coalescence and reflexive and stretching separation is still not entirely understood and a general model for collision outcome boundaries is not available. In this work, the effect of viscosity on the droplet-droplet collision outcome is studied using direct numerical simulations employing the volume of fluid method. The role of viscous energy dissipation is analysed in collisions of droplets with different sizes and different physical properties. From the simulations results, a general phenomenological model depending on the capillary number (Ca, accounting for viscosity), the impact parameter (B), the Weber number (We), and the size ratio (Δ) is proposed.","Viscosity; Collision theories; Drop coalescence; Surface tension; Drop formation","en","journal article","","","","","","","","2018-06-06","","","Intensified Reaction and Separation Systems","","",""
"uuid:dd497400-f848-42e8-bf49-2105f6835c7d","http://resolver.tudelft.nl/uuid:dd497400-f848-42e8-bf49-2105f6835c7d","Simple diffusion hopping model with convection","Fitzgerald, B. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); van Santen, R. (Eindhoven University of Technology)","","2017","We present results from a new variant of a diffusion hopping model, the convective diffusive lattice model, to describe the behavior of a particulate flux around bluff obstacles. Particle interactions are constrained to an underlying square lattice where particles are subject to excluded volume conditions. In an extension to previous models, we impose a real continuous velocity field upon the lattice such that particles have an associated velocity vector. We use this velocity field to mediate the position update of the particles through the use of a convective update after which particles also undergo diffusion. We demonstrate the emergence of an expected wake behind a square obstacle which increases in size with increasing object size. For larger objects we observe the presence of recirculation zones marked by the presence of symmetric vortices in qualitative agreement with experiment and previous simulations.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:05599e93-411c-4e42-a0ee-3b50c76ef43a","http://resolver.tudelft.nl/uuid:05599e93-411c-4e42-a0ee-3b50c76ef43a","A coupled Volume of Fluid and Immersed Boundary Method for simulating 3D multiphase flows with contact line dynamics in complex geometries","Patel, H.V. (Eindhoven University of Technology); Das, S. (Eindhoven University of Technology); Kuipers, J.A.M. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology); Peters, E.A.J.F. (Eindhoven University of Technology)","","2017","","Contact line dynamics; Enhanced Oil Recovery (EOR); Immersed Boundary Method (IBM); Static and dynamic contact angle; Volume of Fluid (VOF); Water flooding","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:f9e8c39b-e4e9-4915-8c15-58dd5d2c642d","http://resolver.tudelft.nl/uuid:f9e8c39b-e4e9-4915-8c15-58dd5d2c642d","Viscoelastic flow simulations in random porous media","De, S. (Eindhoven University of Technology); Kuipers, J. A. M. (Eindhoven University of Technology); Peters, E. A. J. F. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2017","We investigate creeping flow of a viscoelastic fluid through a three dimensional random porous medium using computational fluid dynamics. The simulations are performed using a finite volume methodology with a staggered grid. The no slip boundary condition on the fluid-solid interface is implemented using a second order finite volume immersed boundary (FVM-IBM) methodology [1]. The viscoelastic fluid is modeled using a FENE-P type model. The simulations reveal a transition from a laminar regime to a nonstationary regime with increasing viscoelasticity. We find an increased flow resistance with increase in Deborah number even though shear rheology is shear thinning nature of the fluid. By choosing a length scale based on the permeability of the porous media, a Deborah number can be defined, such that a universal curve for the flow transition is obtained. A study of the flow topology shows how in such disordered porous media shear, extensional and rotational contributions to the flow evolve with increased viscoelasticity. We correlate the flow topology with the dissipation function distribution across the porous domain, and find that most of the mechanical energy is dissipated in shear dominated regimes instead, even at high viscoelasticity.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:94bc9e2b-7ef9-43ec-a3c4-60411dc9cf32","http://resolver.tudelft.nl/uuid:94bc9e2b-7ef9-43ec-a3c4-60411dc9cf32","Viscoelastic flow past mono- and bidisperse random arrays of cylinders: flow resistance, topology and normal stress distribution","De, Sourav (Eindhoven University of Technology); Kuipers, J.A.M. (Eindhoven University of Technology); Peters, E.A.J.F. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2017","We investigate creeping viscoelastic fluid flow through two-dimensional porous media consisting of random arrangements of monodisperse and bidisperse cylinders, using our finite volume-immersed boundary method introduced in S. De, et al., J. Non-Newtonian Fluid Mech., 2016, 232, 67–76. The viscoelastic fluid is modeled with a FENE-P model. The simulations show an increased flow resistance with increase in flow rate, even though the bulk response of the fluid to shear flow is shear thinning. We show that if the square root of the permeability is chosen as the characteristic length scale in the determination of the dimensionless Deborah number (De), then all flow resistance curves collapse to a single master curve, irrespective of the pore geometry. Our study reveals how viscoelastic stresses and flow topologies (rotation, shear and extension) are distributed through the porous media, and how they evolve with increasing De. We correlate the local viscoelastic first normal stress differences with the local flow topology and show that the largest normal stress differences are located in shear flow dominated regions and not in extensional flow dominated regions at higher viscoelasticity. The study shows that normal stress differences in shear flow regions may play a crucial role in the increase of flow resistance for viscoelastic flow through such porous media.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:4cc6803a-b9e9-4ed6-a980-a4072ccf4f20","http://resolver.tudelft.nl/uuid:4cc6803a-b9e9-4ed6-a980-a4072ccf4f20","Particle-based modeling of heterogeneous chemical kinetics including mass transfer","Sengar, A. (Eindhoven University of Technology); Kuipers, J.R. (Eindhoven University of Technology); Van Santen, Rutger A. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2017","Connecting the macroscopic world of continuous fields to the microscopic world of discrete molecular events is important for understanding several phenomena occurring at physical boundaries of systems. An important example is heterogeneous catalysis, where reactions take place at active surfaces, but the effective reaction rates are determined by transport limitations in the bulk fluid and reaction limitations on the catalyst surface. In this work we study the macro-micro connection in a model heterogeneous catalytic reactor by means of stochastic rotation dynamics. The model is able to resolve the convective and diffusive interplay between participating species, while including adsorption, desorption, and reaction processes on the catalytic surface. Here we apply the simulation methodology to a simple straight microchannel with a catalytic strip. Dimensionless Damkohler numbers are used to comment on the spatial concentration profiles of reactants and products near the catalyst strip and in the bulk. We end the discussion with an outlook on more complicated geometries and increasingly complex reactions.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:f7598557-a3cf-4337-8ffb-3669881de9af","http://resolver.tudelft.nl/uuid:f7598557-a3cf-4337-8ffb-3669881de9af","Magnetic particle tracking for nonspherical particles in a cylindrical fluidized bed","Buist, Kay A. (Eindhoven University of Technology); Jayaprakas, Pavithra (Eindhoven University of Technology); Kuipers, J.A.M. (Eindhoven University of Technology); Deen, Niels G. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems)","","2017","In granular flow operations, often particles are nonspherical. This has inspired a vast amount of research in understanding the behavior of these particles. Various models are being developed to study the hydrodynamics involving nonspherical particles. Experiments however are often limited to obtain data on the translational motion only. This paper focusses on the unique capability of Magnetic Particle Tracking to track the orientation of a marker in a full 3-D cylindrical fluidized bed. Stainless steel particles with the same volume and different aspect ratios are fluidized at a range of superficial gas velocities. Spherical and rod-like particles show distinctly different fluidization behavior. Also, the distribution of angles for rod-like particles changes with position in the fluidized bed as well as with the superficial velocity. Magnetic Particle Tracking shows its unique capability to study both spatial distribution and orientation of the particles allowing more in-depth validation of Discrete Particle Models.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:fa3d1ee7-6779-4aac-a95c-cb9484884ede","http://resolver.tudelft.nl/uuid:fa3d1ee7-6779-4aac-a95c-cb9484884ede","Fluidization of spherocylindrical particles","Mahajan, V.V. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology); Nijssen, Tim M.J. (Eindhoven University of Technology); Fitzgerald, B. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology); Hofman, Jeroen (Eindhoven University of Technology); Kuipers, Hans (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology)","","2017","Multiphase (gas-solid) flows are encountered in numerous industrial applications such as pharmaceutical, food, agricultural processing and energy generation. A coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach is a popular way to study such flows at a particle scale. However, most of these studies deal with spherical particles while in reality, the particles are rarely spherical. The particle shape can have significant effect on hydrodynamics in a fluidized bed. Moreover, most studies in literature use inaccurate drag laws because accurate laws are not readily available. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation with the flow, Reynolds number and packing fraction. In this work, the CFD-DEM approach is extended to model a laboratory scale fluidized bed of spherocylinder (rod-like) particles. These rod-like particles can be classified as Geldart D particles and have an aspect ratio of 4. Experiments are performed to study the particle flow behavior in a quasi-2D fluidized bed. Numerically obtained results for pressure drop and bed height are compared with experiments. The capability of CFD-DEM approach to efficiently describe the global bed dynamics for fluidized bed of rod-like particles is demonstrated.","","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""
"uuid:aba11fba-837b-4a26-b73c-62764d54cdb9","http://resolver.tudelft.nl/uuid:aba11fba-837b-4a26-b73c-62764d54cdb9","Three-dimensional fluidized beds with rough spheres: Validation of a Two Fluid Model by Magnetic Particle Tracking and discrete particle simulations","Yang, L. (Eindhoven University of Technology); Padding, J.T. (TU Delft Intensified Reaction and Separation Systems); Buist, K. A. (Eindhoven University of Technology); Kuipers, J.R. (Eindhoven University of Technology)","","2017","Two fluid model simulations based on our recently introduced kinetic theory of granular flow (KTGF) for rough spheres and rough walls, are validated for the first time for full three-dimensional (3D) bubbling fluidized beds. The validation is performed by comparing with experimental data from Magnetic Particle Tracking and more detailed Discrete Particle Model simulations. The effect of adding a third dimension is investigated by comparing pseudo-2D and full 3D bubbling fluidized beds containing inelastic rough particles. Spatial distributions of key hydrodynamic data as well as energy balances in the fluidized bed are compared. In the pseudo-2D bed, on comparison with the KTGF derived by Jenkins and Zhang, we find that the present KTGF improves the prediction of bed hydrodynamics. In the full 3D bed, particles are more homogeneously distributed in comparison with the pseudo-2D bed due to a decrease of the frictional effect from the front and back walls. The new model results are in good agreement with experimental data and discrete particle simulations for the time-averaged bed hydrodynamics.","Discrete Particle Model; Fluidization; Frictional collision; Magnetic Particle Tracking; Rough particles; Two-Fluid Model","en","journal article","","","","","","","","","","","Intensified Reaction and Separation Systems","","",""