Searched for: subject%3A%22Natural%255C+convection%22
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Rajora, A. (author), Haverkort, J.W. (author)
Understanding multiphase flow close to the electrode surface is crucial to the design of electrolyzers, such as alkaline water electrolyzers for the production of green hydrogen. Vertical electrodes develop a narrow gas plume near their surface. We apply the integral method to the mixture model. Considering both exponentially varying and step...
journal article 2023
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Vesper, J.E. (author), Tietjen, Sebastian C. (author), Chakkingal, M. (author), Kenjeres, S. (author)
In the present study, we analyse individual and combined effects of conductive horizontal walls and conductive fins on the natural convection of air in side heated cavities (SHC). The flow and heat transfer are studied for Rayleigh numbers in the range of 10<sup>4</sup>−−10<sup>9</sup>: Direct Numerical Simulation (DNS) is conducted for the...
journal article 2022
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Safari, Vahid (author), Kamkari, Babak (author), Hooman, K. (author), Khodadadi, J. M. (author)
Widespread commercialization of PCM-based latent heat storage systems is limited by the low melting and solidification rates during the phase transition process. In this study, fins are used to enhance the phase change process. A parametric study is conducted to understand the effect of fins on the thermal performance of vertically- and...
journal article 2022
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Koolstra, Rense (author)
Porous media are used for a wide variation of applications in energy production and storage. One of those applications is the storage of heat which are of great importance in the renewable energy transition. Most literature reported limit itself only to one single thermal conductivity for the porous media. In reality however, the porous media...
master thesis 2020
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Chakkingal, M. (author)
Heat transfer by the motion of fluids, referred to as convective heat transfer, is ubiquitous. Convective heat transfer in enclosures packed with solid obstacles, is of great importance in various engineering and real-life applications, such as in blast furnaces, refrigeration devices, distribution transformers, nuclear waste disposal, energy...
doctoral thesis 2020
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Li, Zhongtian (author)
HVAC cable is normally installed in a PE (Polyethylene) pipe underground. The pipe is placed in the underground path formed by horizontal directional drilling (HDD). During power transmission, the generated heat from the cable is dissipated by natural convection of water in the gap between cable and pipe. In this project, the first part focuses...
master thesis 2020
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Ataei Dadavi, I. (author)
In the chain of steel production, the blast furnace converts iron ore into liquid iron. The hearth of the blast furnace, where the liquid metal is collected and tapped off, is filled with relatively large coke particles (D ~ 20 – 100 mm). The meandering flow of hot liquid metal in the coarse-grained porous medium in the hearth causes erosion of...
doctoral thesis 2020
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Chakkingal, M. (author), Voigt, Roland (author), Kleijn, C.R. (author), Kenjeres, S. (author)
We investigate natural convection driven by a horizontal temperature gradient and a vertical concentration gradient in fluid-filled enclosures with obstructions inside it. Within the domain, nine adiabatic and impermeable cylinders are placed, occupying 30% of the domain volume. The Boussinesq approximation is used to account for density...
journal article 2020
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Chakkingal, M. (author), de Geus, Julia (author), Kenjeres, S. (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author)
We report numerical simulations of assisting and opposing mixed convection in a side-heated, side-cooled cavity packed with relatively large solid spheres. The mixed convection is generated by imposing a movement on the isothermal vertical walls, either in or opposite to the direction of natural convection flow. For a fluid Prandtl number of...
journal article 2020
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Chakkingal, M. (author), Schiavo, Sabino (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author), Kenjeres, S. (author)
We numerically investigate natural convection in a bottom-heated top-cooled cavity, fully and partially filled with adiabatic spheres (with diameter-to-cavity-size ratio d/L=0.2) arranged in a Simple Cubic Packing (SCP) configuration. We study the influence of packing height and location of porous media. We carry out the simulations using...
journal article 2020
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Chakkingal, M. (author), Kenjeres, S. (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author)
We report numerical simulations of natural convection and conjugate heat transfer in a differentially heated cubical cavity packed with relatively large hydrogel beads (d/L=0.2) in a Simple Cubic Packing configuration. We study the influence of a spatially non-uniform, sinusoidally varying, wall temperature on the local flow and heat transfer...
journal article 2020
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Wapperom, Sander (author)
There is a 95% certainty that human activity is the dominant cause of observed warming since the mid-20thcentury [1]. Burning fossil fuels for energy is the dominant cause of greenhouse gas emissions. 32% of the Dutch energy supply is consumed by the built environment. The façade is the largest area of the building envelope. Consequently, the...
master thesis 2019
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Ataei Dadavi, I. (author), Chakkingal, M. (author), Kenjeres, S. (author), Kleijn, C.R. (author), Tummers, M.J. (author)
This paper reports on an experimental study of natural convection in an enclosure that is heated at the bottom and cooled at the top, filled with a packed bed of relatively large solid spheres. Nusselt numbers were measured for various sphere conductivities, spheres sizes and sphere packings for Rayleigh numbers varying between 10<sup>7</sup>...
journal article 2019
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Chakkingal, M. (author), Kenjeres, S. (author), Ataei Dadavi, I. (author), Tummers, M.J. (author), Kleijn, C.R. (author)
We report numerical simulations of fluid natural convection with conjugate heat transfer in a bottom-heated, top-cooled cubical cavity packed with relatively large (d/L=0.2) solid spheres in a Body Centred Tetragonal (BCT) configuration. We study largely varying solid-to-fluid thermal conductivity ratios between 0.3 and 198, for a fluid...
journal article 2019
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Tummers, M.J. (author), Steunebrink, M. (author)
This paper reports on an experimental study of the effects of surface roughness on the flow and heat transfer in cubical Rayleigh-Bénard convection cells for Rayleigh numbers between 10<sup>7</sup> and 10<sup>10</sup>. In the rough cells the top and bottom surfaces are equipped with square arrays of copper cubes. In line with other studies,...
journal article 2019
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Ataei Dadavi, I. (author), Rounaghi, Nima (author), Chakkingal, M. (author), Kenjeres, S. (author), Kleijn, C.R. (author), Tummers, M.J. (author)
Flow and heat transfer in a differentially side heated cubic cavity filled with relatively large solid spheres forming a coarse porous medium have been studied experimentally. Nusselt numbers were measured for Rayleigh numbers between 1.9 × 10<sup>7</sup> and 1.7 × 10<sup>9</sup>, solid-to-fluid conductivity ratios between 0.32 and 618, and...
journal article 2019
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Wani, F.M. (author), Shipurkar, U. (author), Dong, J. (author), Polinder, H. (author)
This paper proposes a simplified approach to model the thermal behavior of the insulated gate bipolar transistors (IGBTs) in a subsea power electronic converter. The models are based on empirical relations for natural convection in water, and IGBT datasheet values. The proposed model can be used in the design of subsea converters and in the...
journal article 2018
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Khosrokhavar, R. (author)
The work described in this thesis deals with a variety of aspects related to the storage of carbon dioxide in geological formations. In particular we focus on the transfer between the gas phase to a fluid (liquid) or solid phase. This thesis limits its interest to study the sequestration capacity of CO2 in saline aquifers and more specifically...
doctoral thesis 2014
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Farajzadeh, R. (author), Meulenbroek, B.J. (author), Daniel, D. (author), Riaz, A. (author), Bruining, J. (author)
In this paper, we follow a similar procedure as proposed by Koval (SPE J 3(2):145–154, 1963) to analytically model CO2 transfer between the overriding carbon dioxide layer and the brine layer below it. We show that a very thin diffusive layer on top separates the interface from a gravitationally unstable convective flow layer below it. Flow in...
journal article 2013
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Ranganathan, P. (author), Farajzadeh, R. (author), Bruining, J. (author), Zitha, P.L.J. (author)
We report a modeling and numerical simulation study of density-driven natural convection during geological CO2 storage in heterogeneous formations. We consider an aquifer or depleted oilfield overlain by gaseous CO2, where the water density increases due to CO2 dissolution. The heterogeneity of the aquifer is represented by spatial variations of...
journal article 2012
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