Latent heat storage using phase change materials (PCMs) is a promising technology for storing and recovering waste heat. PCMs offer high energy density and can be tailored for specific melting temperatures, making them suitable for various applications, including temperature stabilization in buildings and thermal management of electronics and batteries. However, a significant disadvantage of PCMs is their low thermal conductivity, which slows the process of charging and discharging thermal energy. This work explores a novel approach to enhance the melting rate of PCMs by incorporating thermally conductive objects (TCOs) within the PCM. The TCO density lies between the solid and liquid PCM densities and is designed to follow the solid-liquid interface. First, an analytical model based on the Stefan problem formulation and a numerical model developed using Ansys Fluent, with locally modified thermal conductivity at the solid-liquid interface, were created to simulate the thermal behavior of the PCM with the addition of TCOs. An experimental setup, consisting of a rectangular enclosure with an organic paraffin as the PCM and hollow aluminum cylinders as the TCOs, was employed to validate these models under purely conductive melting conditions, with heating from the top and cooling from the bottom. Experimental results indicate that the addition of cylinders increased the melting rate by 19% under purely conductive conditions compared to the scenario without cylinders. However, the cylinders enhanced heat flux only within the first 12 mm, beyond which the thermal resistance of the liquid PCM became dominant, preventing further heat flux improvements. During solidification, the cylinders did not move with the solid front and were engulfed at the bottom. In the second part of this work, the developed Fluent model is used to study hypothetical scenarios where a TCO is added to the PCM, but heating comes from the side walls and melting is driven by convection. In this scenario, the inclusion of a TCO at the solid-liquid interface acts as a moving fin, increasing the melting rate by 62% and enhancing thermal power dissipation from 26.5 W to 75.4 W. Future research should focus on experimentally validating this scenario under convective melting, exploring methods to mechanically return the TCO to its starting position for repeatability, and conducting an energy analysis to determine whether the benefits of an enhanced melting rate outweigh the energy required to move the object and the increased manufacturing costs of the latent heat storage system.

In a hydrodynamic journal bearing, the lubricant is pressurized by the relative movement of the bearing surfaces, creating a load-carrying capacity. The load-carrying capacity can be increased by using a lubricant with higher viscosity, at the cost of increased friction. A proposed method to increase the maximum load-carrying capacity, while not increasing the friction at lower loads (or at higher speeds), is by using magnetorheological (MR) fluid as lubricant and electromagnets to generate a magnetic field. MR fluid consists of a carrier fluid with micron-sized magnetic particles suspended. Under the influence of an external magnetic field, the viscosity of the fluid increases as the particles form chain-like structures. Using electromagnets, the magnetic field strength can be adjusted based on the operating conditions of the bearing and the bearing can be semi-actively controlled. The objective of this thesis is to create a visual demonstrator setup, intended for educational purposes, that can be used to investigate the pressure distribution and generated forces in a hydrodynamic half journal bearing using MR fluid and electromagnets. Furthermore, the research objective is to increase the maximum load capacity for a specified minimum film thickness, while not increasing the friction in the hydrodynamic lubrication regime. The test setup was based on an existing setup made by GUNT which is able to show the pressure distribution in a half journal bearing using pressure tubes for various eccentricity ratios. Adaptations to this setup were made to measure the generated forces (horizontal force, vertical force and friction force, defined as the frictional moment divided by the radius of the bearing) and to implement an electromagnet. First, experiments using hydraulic oil were performed to test and improve the performance of the setup. Afterwards, experiments using MR fluid were performed with varying magnetic field strengths. Furthermore, a numerical model based on the two-dimensional Reynolds equation was created and validated with the experimental results. Both the numerical and experimental results showed comparable trends of increasing pressure, horizontal force and vertical force, meaning an increasing load capacity, for increasing eccentricity ratio and applied current. The numerical friction force also increased with increasing eccentricity ratio and applied current, while the experimental friction force only increased with increasing applied current and did not show a clear trend with increasing eccentricity ratio. The magnitude of the forces differed significantly between the experimental and numerical results, where the largest differences were observed for the vertical force and the friction force. Many plausible causes for the differences are identified, such as bearing tolerances, uncertainties in eccentricity and modeling simplifications. A combination of these causes is believed to lead to the observed differences. The increase in pressure, horizontal force and vertical force due to an increase in applied current was found to be much smaller experimentally than numerically. This was thought to be caused by a larger temperature increase in the experimental tests than was modeled and by simplifications used in the numerical model such as neglecting the shearthinning characteristics of MR fluids. The friction force differed even more significantly between the numerical and experimental results. Additionally, this is caused by the small magnitude of the friction force in combination with a test setup that is not accurate enough to measure small forces consistently. The created setup can show the change in pressure distribution when the applied current or eccentricity is changed. It therefore serves as a visual demonstrator setup for an MR lubricated hydrodynamic half journal bearing which can be used for educational purposes. However, demonstrator performance was found to be far from ideal as the changes in fluid column height were very slow because of the high MR fluid viscosity. Performance can potentially be improved by using a different or diluted MR fluid. Despite the large differences between the numerical and experimental results, both can be used to display the potential of semi-active control using MR fluid and electromagnets. It is shown that the maximum load capacity can be increased while not increasing the friction coefficient in the hydrodynamic lubrication regime. Several recommendations have been made for changes to the demonstrator setup to improve performance while keeping the setup simple and elegant. The main recommendations include improving the bearing tolerances, testing with a different or diluted MR fluid, implementing capacitive distance sensors and performing experiments at a more consistent ambient temperature.

This thesis focused on designing and constructing a deoxygenation reactor through a modular experimental setup for Catalytic Hydrogen Combustion (CHC). The developed system aims to enhance hydrogen purification techniques. The setup enables testing various catalysts and conditions to remove oxygen down to 5 ppm in a hydrogen stream.

The experimental system was designed from the ground up due to the lack of detailed information on existing systems. The design includes gas treatment, the catalytic reactor, and a post-process system, with several iterations for modularity and safety.

The final setup successfully removed oxygen in an initial test and allowed flexible reactor configurations for various catalyst tests. The system operated smoothly, maintaining gas composition and ensuring safe operation. The oxygen sensor performed reliably, providing data that aligned with the 1D model after adjustments.

In summary, this thesis lays a strong basis for further CHC research. The developed experimental setup is a robust and adaptable tool for researchers and engineers aiming to improve hydrogen purity for industrial applications.

This thesis addresses a critical challenge in the field of renewable energy, focusing on the efficient utilization of Photovoltaic-thermal (PVT) systems. Much research has already been done on PVT and there exist many thermal simulation models. However, many of the researches done and existing thermal models are restricted to a specific collector archetype which gives less flexibility in experimentation between multiple archetypes. In addition, many experimental researches require a physical setup for measurements and thermal simulation models would need to be altered for different research approaches and collector archetypes. The primary objective of this thesis project is therefore to create a performance simulation framework model that is suitable for the calculation of the thermal and electrical performance for any PVT archetype. It aims to develop and implement a toolbox application encompassing heat transfer models that can establish a foundation for future research on PVT collector optimization, PVT system integration and PVT performance analysis. This toolbox application will be implemented into the PVMD Toolbox Vogt et al. (2022), housed within the Photovoltaic Materials and Devices research group at TU Delft.

Selected PVT collector: This research has visualized that there is a wide variety of PVT archetypes that can be used for current and future generations of PVT collectors. PVT collectors can be combined with heat pumps, refrigeration pumps, phase change materials and multiple forms of heat collection via fluids or air. These combinations can all contribute to high electrical and thermal efficiencies

Numerical heat transfer model and assumptions: It is possible to calculate heat transfer rates of complex designs when using a Finite Element Method (FEM) approach to calculate the heat transfer within the collector. With the proper convective and radiative equations to the environment, the heat transfer inside the collector and to the environment could be calculated without needing an experimental setup.

Performance calculations: The performance calculations gave insight into the simulated behavior of the PVT collector when operating in real-world conditions. Ranging the inclination angle from 0 to 60 degrees showed that the thermal efficiency became around 55% at an irradiance of 800 W/m2 at 45 degrees. It also showed that differences in dimensions like pipe thicknesses and number of pipes did not affect the thermal performance that much. The daily performance calculations illustrated that the thermal energy lost to the environment can be three times as high as the incoming solar energy due to the low ambient temperatures compared to the inflow temperature. In the summer, PVT can achieve high total efficiencies of around 75% making PVT suitable during those times. The economic analysis showed that a PVT collector can have an LCOE of $0.08/kWh which is lower than the $0.13/kWh of conventional PV.

High-powered LED arrays have emerged as a viable alternative to halogen lamp-based arrays for heating silicon wafers to 1000C due to their monochromatic radiosity which can be chosen in an efficient bandwidth for high absorption into silicon, removing the requirement for the pre-soak anneal in traditional systems. However, a gap in literature is found as there are only low temperature applications for LED arrays found (max. 400C), on which the research is focussed around improving the control system design. The high-temperature RTP application for LEDs has not yet been studied in literature or implemented in industry. Advancements over the past decades have sharply increased the radiometric flux and efficacy of LEDs, enabling more and more high-powered applications. However, due to the exceptionally small size and high heat fluxes of high-powered LED chips, junction cooling has traditionally been a major bottleneck for implementing LEDs in demanding applications. For the power levels required in 1000C RTP, the feasibility of LEDs in terms of power output, wafer temperature uniformity and cooling of LED-based heater arrays remains unproven. Through a systems-based approach, a multi-domain fundamental analysis and simulation in the fields of linear algebra, heat transfer, optics, electrical engineering, semiconductor physics, CAD and FEM has been performed. Resultingly, feasibility has been demonstrated for 1000C LED RTP.

Hydrodynamic drag significantly influences the fuel efficiency and operational performance of marine vessels. Gas Injection Drag Reduction (GIDR) techniques, such as Bubble Drag Reduction (BDR), Transitional Layer Drag Reduction (TLDR), and Air Layer Drag Reduction (ALDR), have shown promise in reducing skin friction drag by introducing gas into the boundary layer. However, the influence of hull protrusions, such as sacrificial anodes and fouling, on these techniques remains poorly understood. This research addresses the question: How do the placement and dimensions of upstream cylindrical obstacles affect the formation and stability of gas phases (bubbly, transitional, and air layer) in a turbulent boundary layer (TBL)? To investigate this, protrusions are represented as cylindrical objects placed upstream of the gas injector, exploring their effects on the gas injection regimes in a TBL.

The study examines three gas injection regimes: bubbly, transitional, and air layer. In the bubbly regime, the focus is on bubble morphology and velocity distributions. The transitional regime investigates non-wetted areas and air layer morphology. For the air layer regime, the study examines the length and stability of the air layer near the injector. Image processing techniques are used to distinguish the air layer from the surrounding fluid, providing accurate assessments of the properties of the air layer.

The results demonstrate that cylindrical obstacles have a significant effect on the gas phases. In the bubbly regime, they alter bubble morphology and velocity, producing localized velocity peaks. In the transitional regime, obstacles lead to the formation of non-wetted areas and funnel-shaped regions. For the air layer regime, although the length of the air layer remains mostly unaffected, its stability near the injector is disrupted by upstream obstacles due to wake-induced instabilities. These findings highlight the critical role of obstacle placement and dimensions in shaping gas injection regimes.

Future research is needed to enhance understanding in areas such as the integration of velocity measurements (e.g., Particle Image Velocimetry), widening the experimental field of view to capture more comprehensive flow dynamics, and exploring the impact of various obstacle sizes and geometries. These investigations will be crucial for refining gas injection drag reduction strategies and advancing practical marine applications.

This study aims to develop a methodology for upscaling commercially available latent thermal energy storage systems using salt-hydrate HS48 as a phase change material, with a focus on determining optimal design parameters for different sizes and energy demands. The paper begins with a comprehensive review of phase-change materials' properties, theories, and practical applications in various energy storage systems, including integration into hot water storage tanks with diverse configurations. Subsequently, a research method is introduced, based on heat transfer principles and commercial heat battery specifications, providing a scalable simulation model validated through experimental setups. The model emphasizes two different scales and demonstrates non-linear charging time increases with PCM mass. After optimization, the model is scaled to match a commercially available heat battery's power output, evaluating various configurations based on key independent variables. Results favor the configuration, which consist of twice the number of parallel tubes, as the optimal design for reducing PCM mass, system size, and charging time. While the study shows promising outcomes, it also highlights areas for improvement, such as refining assumptions about phase change behavior and addressing specific application requirements like domestic hot water supply

To anticipate for future demand of sustainable liquid fuels, Zero Emission Fuels B.V. develops a solar powered micro plant which produces methanol from water and carbon dioxide captured from outside air. An intermediate step in this process is the electrolysis of water to create hydrogen which reacts with carbon dioxide to methanol. This study encompasses an integration of the pressurised alkaline electrolysis system, in which problems observed in previous generations of the electrolyser have been solved and functionalities have been added. In addition to that, electrolyte samples are taken after different periods
of operation to investigate electrolyte deterioration over time.

A new Balance of Plant (BoP) has been designed, realised and tested. Eight new features to the system can be distinguished, two of which are included to add functionality: the degasser to decontaminate the carbon dioxide-rich
feed water and the pressure booster to replenish the consumed water at system
pressure. The other features are integrated to enlarge the operational envelope, the determination of which was central to the experiments conducted in this research.
Experiments are conducted to find and characterise the four limitations to the operational envelope: the relative valve opening duty (RVOD), flow stagnation, temperature control and crossover.

The RVOD experiments showed deviations from the modelled valve opening cycles, attributed to additional pressure drops, valve opening interference and smaller discharge volumes. Subsequently a corrected model is presented to improve valve cycle time predictions.
Flow stagnation was investigated at various current densities, pressures and temperatures using camera images and a characteristic temperature response to establish flow stagnation. The results showed a minimum volume flow rate decrease in comparison to the previous system, expressed in parameter 𝑋 which decreased from 3.4 to 0.74 A K bar^-1 cm^-2. The minimum volume flow rate decrease is attributed to the larger number of cells and the increase of the height difference between the stack and buffer tanks.
In the temperature control experiments, steady state temperatures were monitored at different current densities, with and without crossflow fan operation. This resulted in a temperature control map, in which the reachable temperatures for different current density are depicted. Furthermore, electrolyte mass flows are determined and pressure dependency of temperature control was investigated at low current densities, concluding that steady state temperatures are independent from pressures in the 10 bar to 50 bar regime. 
Hydrogen crossover was tested by taking gas samples at different operating conditions and subsequent gas composition analysis in a gas chromatograph; oxygen crossover was determined by an oxygen sensor implemented downstream the hydrogen exhaust. All steady state crossovers values were found to be below the safety limits, concluding that crossover is not limiting in the acquired system on all possible operating points. Overnight diffusion crossover experiments showed that maintaining the system under pressure overnight, keeps crossover values below the safety limit.
In addition to the operational envelope, complementary general characteristics such as power consumption and efficiency are presented and compared to industry and literature. On top of that, unexpected findings, design deficits and other relevant phenomena are described to complete the perspective on system performance and behaviour of the electrolysis system. Due to the electrolyte mist purged into the degasser and pressure booster, the electrolyte deterioration experiments are deemed inconclusive. Moreover, a demister is found to be an essential system feature to include in the next generation electrolyser, because both degasser and pressure booster were damaged by the electrolyte spill.

When experimenting with the compression of a gas similar to the output of a CO2 Direct Air Captureunit using an off-the-shelf lubricated compressor, Zero Emission Fuels B.V.(ZEF) encountered severecondensation, damaging the compressor. This explorative study aims to identify the cause of thisproblem, create a concept solution, and test this concept based on model-supported experimentation.Based on a literature study all theoretical concepts are divided into three solution classes. Twoconcepts are then created and theoretically compared. A concept is selected that is based on theadsorption of water into a solid desiccant.As the concept solution is to operate in a closed system, regeneration of the desiccant needs to befaster than its utilization. For this, an experiment is made where a controlled quantity of inert gas ismoisturized, dried, and used to regenerate a second column. From this it can be concluded that thegas can be dried adequately, and that regeneration can be done thoroughly.A model is made to verify the experiment’s workings, based on models from literature. This modelis then validated using literature, and then fitted to experimental data. Combining experiment andliterature data, three key performance indicators are calculated: Cyclic capacity, energy usage, anddesorption rate. The design tools and models developed throughout this thesis are used to size thenext iteration of the concept according to the needs of ZEF.From this, it is concluded that the presented concept is indeed viable to prevent, rather than solve,the problem stated at the start of this thesis. Recommendations are done concerning further develop-ment of the prototype, experiments, model, and overall system

This research studies the fluid-structure interaction (FSI) of compliant surfaces in air flows, with an objective of finding possible turbulent viscous drag reduction. A compliant surface is a thin layer of viscoelastic material drawing inspiration from dolphin epidermis, which was thought to have drag-reducing capabilities by Gray (1936). Research into the drag reduction capabilities of compliant surfaces has been long going for more than five decades, starting with Kramer (1960), yet no firm conclusion has been reached. In addition, most of the experimental research has been focused on water flows, with air flows regarded as incapable of inertially forcing a compliant surface to deform. This research attempts to disprove this assumption by applying the proper inertial scaling to the FSI between the compliant surface and air flows. Compliant surfaces are characterised by the stiffness and thickness, which are presumed to be of first-order influence on the FSI. A parameter sweep of these compliant surface properties was conducted by drag delta measurements and flow visualisation by planar particle image velocimetry (PIV) in the M-Tunnel at the Low Speed Laboratory (LSL) Drag delta results confirm the possibility of turbulent viscous drag reduction by compliant surfaces, with a measured drag delta of -3.43 %. This result is further supported by the decrease in 1D turbulence intensity at the test plate's trailing edge from hot-wire measurements, and a smaller decay of the shape factor H from PIV. Quadrant analysis of the PIV data found evidence of a reduction in combined Q2 and Q4 events, further supporting the drag delta measured. Correlation between the compliant surface's viscoelastic properties and the drag delta found a negative correlation between the magnitude of complex shear modulus and a positive correlation between the loss tangent and drag reduction. The high loss tangent for the drag-reducing compliant surface and its subtle positive correlation with the drag reduction indicates that the viscoelasticity might have a greater influence on the FSI than expected.

As the world population is increasing and cities grow faster than before, food scarcity becomes a bigger issue. To depend less on import and decrease CO2 footprint, food should be produced nearby its consumers. A good solution for food production is a greenhouse which provides a steady high yield throughout the year. Some of the world's fastest growing cities are in Subtropical climates. Subtropical climates are characterized by high temperatures, abundance of sun and high humidity. Due to the high temperatures, cooling in greenhouses in subtropical climates is necessary, but evaporative cooling is not sufficient due to the high humidity. Outside air can be dehumidified by a liquid desiccant to cool the air further with an extra evaporative cooling step. After dehumidifying the air, the absorbed moisture from the air in the desiccant must be removed from the desiccant solution for re-use. This requires a lot of energy, which makes this cooling technique for greenhouses in subtropical climates not economically feasible. The proposed solution is to remove moisture from the desiccant by making use of the hot air that can be collected in the top of the greenhouse. The potential of this solution is assessed in this study. To predict the transfer of mass and heat between air and a calcium chloride solution as desiccant, a mathematical model of the process of mass and heat transfer over a structured cardboard pad is made. An experiment is conducted to validate the mass and heat transfer coefficients of the model. The model is used to evaluate the workings of the proposed system of regeneration. Results show that dehumidification can significantly lower the inlet temperature of the air in the greenhouse, provided that the inlet temperature of the desiccant is low. Regeneration of the desiccant solution with hot air is also possible, provided that the air in the greenhouse is significantly heated by the sun and pre-heating of the desiccant before regeneration is beneficial. The direct coupling of these two systems is not sufficient due to the big difference in temperature of the desiccant that is required at the inlet of the dehumidifier and regenerator. In future work attention should be paid to this temperature difference which is currently limiting the performance of the system. Then it's possible for the concentration of the desiccant to be brought back to the starting conditions for the dehumidifier.

Zero Emission Fuels B.V. (ZEF) is a start-up company developing a fully autonomous methanol synthesis micro-plant that will be energy driven by solar panels. The process implements an alkaline water electrolyzer, which supplies the methanol synthesis reactor with hydrogen. The electrolysis system includes a small-scale stack of cells and is designed to operate at 90 ^oC and the high pressure of 50 bar, with a 30% potassium hydroxide electrolyte. The system is also self-pressurized through the continuous accumulation of the electrolysis gases in the closed flash separation vessels. To control the process, the company has designed a novel system that aims to maintain the gas pressure at 50 bar and the liquid electrolyte level inside the flash separators at a fixed point. 
The present work has two main objectives. The first is to characterize the transient dynamic response of the company's current experimental electrolysis setup under the effect of the operating conditions and control. The second objective is to predict the level of gas crossover that is induced during the system's operation and evaluate the risk of explosive mixtures formation. Two different models were developed to fulfill the research targets.
The first model is based on a 1-d transient hydraulic network analysis. Simulations were conducted using Simulink for a current density range of 500-5000 A/m². The model predicts the electrolyte flow and pressure response in the various elements and locations of the network respectively, indicating also the oscillatory behavior induced by the operation of the valves. A key finding is the high differential pressure between the stack anodes-cathodes that is caused when the valves open, posing a danger for the integrity of the separators between the half-cells.
The second model was developed in MATLAB and uses the predicted flow response of the first model to estimate the crossovers by solving numerically the unsteady 1-d advection-diffusion equation in the corresponding elements. The effect of the supersaturated electrode boundary layer was also considered as an enhancing parameter of the mass transport through the separators of the cells and a sensitivity analysis was conducted. The main finding is that this parameter has an important effect, especially on the hydrogen crossover inducing 1% higher hydrogen impurity when it is increased by a factor of 10. The crossovers of both hydrogen and oxygen are found to gradually increase and reach an almost stable value under the effect of the control system. A comparison of the model with preliminary experimental data indicates a supersaturation intensity between 5 and 15 times higher than the solubility of the components. In this range, the system will safely operate above 2000 A/m² without the formation of explosive mixtures. 

The work presented in this report investigates the effect of replacing natural gas fuel in a radiant tube burner in an industrial furnace with hydrogen fuel. The flue gas is fully contained inside the radiant tube burner and does not come into contact with the iron products inside the furnace. The burner interacts with the process side of the furnace only by heat transfer. Therefore, the investigation could be divided into a study of two separate systems: the burner and the furnace systems. In the first part, the burner system was evaluated. The impact of changing the fuel of the burners from natural gas to hydrogen on heat-, flow- and radiation of the existing burner was studied. Moreover, the NOx generation has been considered. The investigations were performed using Reynolds Average Navier Stokes (RANS), Computational Fluid Dynamics (CFD) approach using detailed chemistry. Natural gas combustion was simulated as the basis for comparison. The result shows that the CFD model could estimate the NOx emission of the base case well. Next, the combustion with hydrogen was compared. The result suggests that the thermal efficiency of the burner is slightly higher with hydrogen fuel. On the other hand, the NOx emission is significantly higher. A modified burner including internal flue gas recycle was proposed and studied. The result shows that the modified burner can be operated at the same power and the same level of NOx emission as the existing system. Furthermore, different burner power could be applied in order to comply with the NOx emission limit or to increase processing speed. In the second part, a heat transfer analysis of the furnace has been performed. The model agrees well with measured data of furnace atmosphere temperature. The result suggests that having a higher burner power could increase the processing speed and reduce the energy requirement per ton of iron products.

The purpose of this study was to create a theoretical model for the distillation of synthetic crude oil (syncrude) into straight-run naphtha, kerosene and gas oil fractions, at a scale of 235 ktfeed/year. To that end, a process model was created that receives the output of a Co-LTFT process as raw feed. The raw feed was prefractionated to remove the majority of the unreacted syngas, inert gases, light hydrocarbons (C1-C4) and water. The remaining stream was syncrude, primarily composed of alkanes and 1-alkenes in the C5-50 range.
A Base Case was designed in ASPEN plus, with a distillation unit with two steam strippers and three pumparounds. The goal was to receive the syncrude and separate naphtha, kerosene and gas oil cuts, with least 90% purity and recovery of the components. The Fenske-Underwood-Gilliland method was used to estimate the number of stages and reflux ratio of the column, and the Kirkbride method was used to find an initial estimate for the feed stage. The TBP curves of the cuts were compared with similar cuts from literature and found to be similar.
The Base Case underwent a sensitivity analysis in order to ascertain the effect of different design and process parameters on the separation quality and utility consumption. The parameters that were tested are cold condensate temperature, feed stage, condenser duty, feed temperature and stripping steam flow rate to the ADU. According to the sensitivity analysis results, for optimal separation between the syncrude and the other gases in the raw feed, the gases must be purged at a temperature of -70°C. Furthermore, the optimal configuration for the distillation of the given syncrude into naphtha, kerosene and gas oil fractions with at least 90% purity and recovery is as follows: The ADU has 40 equilibrium stages and a condenser duty of approximately -5.7 MW. The feed must be heated to 310°C and enter the column at stage 37. The stripping steam flow rate must be around 1.3 kg/s.
Five alternative processes were modelled as well, with similar inputs to the column model, and the results of the distillate separation quality and utility consumption were documented as well. The alterations of the alternative cases include replacing the stripping steam with a reboiler in one of the strippers, adding a stripper from where an additional product was drawn, concentrating the pumparound duty on the condenser, using a vacuum distillation unit to fractionate the residue of the atmospheric distillation unit, and employing a heat integration network.
The most important conclusions are listed. Firstly, the side strippers must use low pressure stripping steam instead of reboilers. Next, the minimum number of products must be drawn off in order to minimize utility consumption at a given separation quality. Furthermore, heat integration can save up to 50% in total utility consumption (heat and cooling water). It is recommended that further research, including a cost estimation, is conducted on refineries that produce on-specification final products.

Increase in global energy demand has brought to a massive rise in greenhouse gases emissions. In particular, the continuously increasing atmospheric concentration of carbon dioxide is a major concern among the scientific community. This paved the way for an intense research of CO2 emissions mitigating technologies. Those ones including carbon capture, storage and utilisation are seen as part of the solution for this global problem. In this framework, Zero Emission Fuels (ZEF), a startup company located in Delft (The Netherlands) set the ambitious goal of developing a micro process plant producing methanol from ambient air and sunlight only. Part of the process involves direct capture of carbon dioxide from the atmosphere (direct air capture) with the use of a pure tetraethylenepentamine (TEPA) absorbent. ZEF sets itself aside from the rest of the industry developing an absorber which collects CO2 with no support structure by continuously flowing TEPA inside open channels. Previous research shows how this approach brings limitations connected to slowly diffusing CO2 molecules in the absorbent liquid film in proximity of the gas-liquid interface. In this framework, circulation of TEPA particles from the gas-liquid interface into the bulk of the flowing absorbent is seen as a viable solution to improve the process. This thesis focuses on investigating this hypothesis by inducing mixing on the liquid side. That is done by building two experimental setups investigating both passive and active mixing. Experimental results show that active mixing can be used to improve the rate of CO2 absorption, while passive mixing does not bring significant advantages. Results from the passive mixing experiments are further investigated by modelling the fluid dynamics of the process through a Direct Numerical Simulation of the particular Stokes’ flow in the engineered absorption channel. The process is characterised with the definition of a theoretical framework describing mass transfer in the liquid side. Following an analogy with ice formation on top of a frozen lake, this theory, also known as the ”Ice-Sheet” theory, shines some light on the way this diffusion limitations are happening at a molecular level. In particular, a highly viscous, heavily loaded layer of sorbent on the gas-liquid interface is believed to be the cause for observed CO2 diffusion limitations. This theory is backed-up by defining its mathematical equivalent in the form of a mass transfer model. Comparing the results of the model with experimental results, a very good agreement is observed. That is believed to add credibility to the proposed theory. Moreover, that is also found to be in line with the latest knowledge available in literature about CO2 absorption in TEPA films. Finally, the experimental results and the developed models are used to engineer a new iteration of ZEF’s absorber on a cost reduction basis.

The drainage time of liquid-filled PET bottles can be greatly reduced by pre-rotating the bottle with a certain angular velocity. Depending on the magnitude of the angular velocity, up to four different flow regimes can be distinguished during the emptying of a bottle: bubble regime, transition regime, vortex
regime and the swirl regime. At zero or low pre-rotation, the flow is in the so-called bubble regime in which the intermittent downward liquid flow is accompanied by an upward motion of irregularly shaped air bubbles into the bottle. At sufficiently high pre-rotation, the picture is completely different. After
initial transient behaviour in which the flow is first in the bubble regime, the flow undergoes transition towards a so-called vortex regime. This is characterized by regular downward motion of liquid along the bottle wall in a free-surface vortex and accompanying upward motion of air through the nozzle core. Finally, close to the end of the drainage process another transition towards a so-called swirl regime takes place, in which the last bit of liquid swirls around in the bottle before being slowed down sufficiently to exit the bottle through the nozzle opening. Dimensional analysis indicates that for a specific bottle geometry the non-dimensional total drainage time td/td,0, where td,0 is a characteristic drainage time scale for stationary low-viscosity fluids in the bubble regime, depends primarily on 3 non-dimensional numbers: (1) the rotation number, Π (2) the Morton number, Mo, and (3) the E¨otvos number, Eo. The former represents the characteristic ratio of centrifugal to hydrostatic forces inside the liquid phase. The objective of this study is to determine the relationship between the non-dimensional drainage time and Π and gain insight in the influence of E¨otvos and Morton onto this. To this purpose, a parametric CFD study of a model PET bottle has been conducted and the results have been compared with previous preliminary experiments performed in our group. The numerical study is divided into three categories, each discussing the influence of one of the dimensionless parameters. The influence of the Π-number was studied by altering the initial rotational velocity of the bottle. It was found that at some critical Π-number, the drainage time was minimal. A further increase beyond the critical Π-number resulted in a longer drainage time, due to the stronger centrifugal force acting on the liquid layer. It was found through an analytical solution and verified with the numerical results that the rate at which the Π-number grows in relation to the dimensionless drainage time is to the power 3 for the laminar case and to the power 3/2 for the turbulent case. Below the critical value, the flow is expected to remain in the so-called bubble regime, also increasing the drainage time. Furthermore, the onset of the vortex regime was expected to occur at a constant value of Π. This was also verified with the numerical results and a strong correlation was found between the onset and the corresponding local Π-number. The influence of the Morton number is also discussed, where an increase in the Morton number was realized with an increase in viscosity. It was found that the drainage time got substantially reduced with an increase in viscosity. The effects of viscous dissipation resulted in a bigger effective area and higher axial downward flow velocity. However, increasing the Morton number excessively would result in the flow regime remaining in the bubble regime. Therefore, the critical Πnumber shifts depending on the different fluid compositions. When varying the E¨otvos number, by both changing the viscosity and the surface tension, it was found that the latter had negligible effect on the generation of the air-core or the drainage time.

When placing orders of new vessels, shipowners are most concerned about two things: how much they need to pay and how long they need to wait, and the estimation of newbuilding prices and lead times for new vessels is important to both shipowners and shipbuilders. This thesis introduces the generalized additive model (GAM) as the specific regression method, explains what factors are influential to newbuilding prices and lead times of bulk carriers, and illustrates how to use GAM to construct the estimation models

In some countries, drying processes use up to 20% of the total energy consumption. Within the agriculture sector, drying of food and flowering products is a necessary step in production. A lot of companies make use of hot air dryers where the heat is gained by burning natural gas. A novel method is to use a heat pump assisted drying systems instead. Heat pump assisted drying realises a better product quality due to the ability of humidity and climate control of the drying medium: air. Additionally, there are possibilities for energy savings up to 50%. This thesis project is mentioned as the first step for an initiative to introduce heat pump drying into the horticulture sector. The project started almost 1 year ago and is still far from finished. Main goal was to get a good understanding of the product drying behaviour, drying capacities and the system requirements and footprints. Conclusions should determine whether there is a possibil-ity for market implementation or not. The results in this report are promising. Heat pump drying is a trending research topic in science, where new developments on predicting the dynamic drying behaviour of agricultural products show up every month. This study involves a computational model, where the dynamic process of drying flower bulbs is simulated. This model is validated by measurements on existing drying in-stallations. Building this model resulted in a good understanding about the flower bulb characteris-tics and the necessary drying capacities. Additionally, Heat pump drying systems are evaluated and a dynamically modelled. When both models are the drying process of FB’s can be optimized. The first protype of the HP drying system that will be used in further research will be shortly discussed. Conclusion of this report is that heat pump drying is a promising technique for drying of FB’s. The combination of technical advantages with energy savings, could lead to better product quality and lower production costs. The business case is strengthened by future perspectives where energy efficiency and reduction of CO2 emissions will more and more important due to climate change.

Climate change is an inevitable fact and governments worldwide have started to recognize this by expanding the contribution of renewable energy sources to our global energy production. Wind energy is currently one of the most attractive solutions for the transition to a more sustainable energy future. Since wind energy is not the only competitor in this journey towards a greener earth, reduction of the Levelized Cost of Energy (LCoE) is an important indicator to stay competitive. The wind industry pursues this goal primarily by increasing the size of wind turbines. As a result, the increased rotor size also comes with a significant increase in static and fatigue loading on the wind turbine’s rotating and fixed structure. To address this problem, the industry continues to investigate the application of alternative and economically more viable drivetrain technologies. An interesting development highlights that the implementation of robust compact hydraulic wind turbine drivetrains presents such an alternative. Hydraulic transmission systems are typically employed in high-load systems and form an excellent opportunity for application in multi-megawatt turbines. The Delft Offshore Turbine (DOT) is a hydraulic wind turbine concept which replaces conventional drivetrain components with more robust hydraulic components. It substitutes the conventional power-train inside the nacelle with a single seawater pump. Pressurized seawater is directed through the high-pressure discharge line to a combined Pelton turbine, connected to an electrical generator on a central multi-megawatt electricity generation platform. Moreover, the low-pressure feed line, directing seawater to the seawater pump, also has to maintain a certain pressure to prevent cavitation in the pump cylinders. This requires energy, which forms an issue since the availability of electrical energy is not self-evident on offshore locations. The goal of the DOT concept is to be completely self-sustainable and independent of external power sources. One solution for this problem is the extraction of hydraulic energy from the pressurized seawater inside the high-pressure discharge line before it is harvested by the Pelton turbine. This mechanism is referred to as the turbine’s
Regenerative Power System (RPS), and adds up to the challenge of hydraulic turbine control. This thesis presents the modeling, control design and control evaluation for this intermediate version of the DOT concept. Besides rotor speed control, also the feed line pressure and the regenerative power system have to be regulated. Decentralized gain scheduled SISO controllers are employed and evaluated in below-rated conditions. Using off-the-shelf components, it is shown that the overall drivetrain efficiency and controllability are increased for operation at maximum rotor torque in the below-rated (partial load) operational region.

Rising concentration of CO2 in the atmosphere has become a significant concern, paving the way for worldwide research on mitigation techniques like carbon capture and storage (CCS) and carbon capture and utilization (CCU). Zero Emission Fuel (ZEF), an aspiring startup based in the Netherlands, aims to develop a micro plant that produces methanol from just solar energy and air. Their process involves capturing CO2 and H2O directly from the air, splitting H2O to obtain H2 and producing methanol by reacting CO2 with H2. The focus of this research is on the absorption process of ZEF's direct air capture unit. Instead of capturing CO2 and H2O through a widely used batch direct air capture process, ZEF chooses to side with a novel continuous absorption and desorption process involving a flow of bulk polyamines without any conventional support structures. Polyethyleneimine (PEI-MW-600) and Tetraethylenepentamine (TEPA) are used as absorbents to achieve a target of capturing 825 grams of CO2 in 8 hours every day from a single direct air capture unit. Preliminary investigations show that the viscosity of PEI-600 is significantly higher than that of TEPA. An increase in CO2 concentration increases the viscosity of both polyamines significantly. In comparison, increasing H2O concentration leads to a maximum viscosity point in both polyamines and subsequent decrease in viscosity with a further increase in H2O concentration. Although, compared to CO2, H2O has a smaller effect on viscosity. Moreover, premixed samples of PEI-600 and TEPA with H2O show an increase in the CO2 absorption rate when pure CO2 is bubbled through the samples. In order to study and characterize the novel absorption process, an experimental setup facilitating a flow of absorbent is developed, and experiments are conducted following an experimental approach to calculate the mass transfer rates and average concentrations of CO2 and H2O. Fourier-transform infrared spectroscopy is used to estimate these concentrations. Experiments are performed on different initial concentrations of PEI and TEPA. TEPA is found to have a better absorption performance with an average CO2 absorption rate that is two times higher than PEI-600. Contrary to preliminary investigations done by bubbling CO2 into polyamines, absorbents with premixed water flowing down a channel were found to have lower CO2 absorption rates than pure polyamines. A multiple regression viscosity model, heat model, and a model of absorption column is developed using the data collected to estimate average viscosity, the heat of absorption of water, and characteristics of the absorption process. Diffusion of CO2 through the absorbent layers is found to be the primary limiting factor, while mass flow rates of absorbent and air are also found to influence the absorption process. Finally, a design of the absorption column is made to meet ZEF's requirement taking into account various performance characteristics studied during the thesis.