The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Seung Wook Baek - One of the best experts on this subject based on the ideXlab platform.
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effects of surface radiation on the unsteady natural convection in a Rectangular Enclosure
International Journal of Aeronautical and Space Sciences, 2002Co-Authors: Seung Wook Baek, Taigyoung KimAbstract:Numerical solution of the full Navier-Stokes equation as well as the energy equation has been obtained for the unsteady natural convection in a Rectangular Enclosure. One side wall was maintained at very high temperature simulating fires. Especially the effect of surface radiation was taken into account. While the enclosed air was assumed to be transparent, the internal walls directly interacted one another through the surface radiation. Due to a significant temperature difference in the flow field, the equation of state was used instead of the Boussinesq approximation. It was found that the rapid heating of the adiabatic ceiling and floor by the incoming radiation from the hot wall made the evolution at thermo-fluid field highly unstable in the initial period. Therefore, the secondary cells brought about at the floor region greatly affected the heat transfer mechanism inside the Enclosure. The heat transfer rate was augmented by the radiation, resulting in requiring less time for the flow to reach the steady state. At the steady state neglecting radiation two internal hydraulic jumps were clearly observed in upper/left as well as in lower/right comer. However, the hydraulic jump in the lower/right comer could not be observed for the case including radiation due to its high momentum flow over the bottom wall. Radiation resulted in a faster establishment of the steady state phenomena.
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AN UNSTEADY CONDUCTION AND TWO-PHASE RADIATION IN A 2-D Rectangular Enclosure WITH GAS AND PARTICLES
Numerical Heat Transfer Part A: Applications, 2002Co-Authors: Seung Wook Baek, Hyung Ju LeeAbstract:A problem of combined conductive and two-phase radiative heat transfer in a two-dimensional Rectangular Enclosure with two-phase (gas-particles) media is analyzed. A two-phase radiative transfer equation (RTE) considering radiation by both gas and particles is studied. Its nonlinear integrodifferential RTE is solved using the discrete ordinates method (DOM, or so-called S N method). To validate the program, we compare the solution in a two-dimensional Rectangular black Enclosure with others. The DOM is then applied to the unsteady thermal development in two-phase media contained in a Rectangular Enclosure. A parametric study is performed by changing the gas and particle absorption coefficients, particle number density, particle emissivity, wall emissivity, and aspect ratio of the Enclosure. The results confirm a significant effect of the two-phase radiation on the thermal development in the geometry. However, it is found that the conduction is predominant near the hot wall.
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the effects of radiation on natural convection in a Rectangular Enclosure divided by two partitions
Numerical Heat Transfer Part A-applications, 2000Co-Authors: Cho Young Han, Seung Wook BaekAbstract:The phenomena of radiation-affected steady-laminar natural convection in a Rectangular Enclosure with two incomplete partitions are numerically examined under a large temperature difference. Pure convection, convection with surface radiation, and convection with surface rgas radiation are considered and compared. To examine the effects of two incomplete partitions on thermofluid dynamics behavior, they are assumed to be very thin ( ) and adiabatic. The finite-volume method FVM is used for solving the radiative transport equation, assuming that partitions are radiatively opaque. After validating the numerical procedures, the detailed radiation effects were sought. Based on the results of this study, it was found that the radiation played a significant role in developing the fluid dynamic and thermal distributions compared with cases without radiation. Once radiation was involved, the surface radiation was dominant over the gas radiation. The baffle configuration was also found to affect the results of radiation.
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Ignition phenomenon of solid fuel in a confined Rectangular Enclosure
International Journal of Heat and Mass Transfer, 1996Co-Authors: Seung Wook Baek, Taik Young Kim, Carolyn R. KaplanAbstract:Abstract In this study the ignition model of a PMMA (polymethyl-methacrylate) wall has been proposed in a two-dimensional Rectangular Enclosure when it is initially exposed to a high-temperature source. The effect of surface radiation has been taken into account. It was found that the transient development of thermo-fluid fields was strongly governed by wall heating due to surface radiation. In particular, the rapid heating of the adiabatic floor made the flow very unstable, creating complex secondary recirculating flows. Depending on the hot source temperature, the ignition process was controlled either by mixing and transport of fuel vapor and oxidizer in the vicinity of the hot wall, or by infiltration of hot air into the region near the PMMA wall. Copyright © 1996 Elsevier Science Ltd.
El Khadir Lakhal - One of the best experts on this subject based on the ideXlab platform.
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NUMERICAL INVESTIGATION OF HEAT TRANSFER DURING SOLIDIFICATION IN A Rectangular Enclosure WITH INTERNALLY HORIZONTAL PARTIAL FINS
Computational Thermal Sciences, 2015Co-Authors: Laila Khatra, Hamid El Qarnia, Mohammed El Ganaoui, El Khadir LakhalAbstract:The paper aims to investigate numerically the thermal and flow characteristics of an internally finned Rectangular Enclosure during the solidification process of a superheated phase change material (PCM). This work is motivated by the need to intensify heat transfer and accelerate the discharge process in latent heat storage units. A mathematical model is developed and a fixed-grid enthalpy formulation is adopted for modeling the solidification process coupling with convection-conduction heat transfer. The finite volume method was used for discretization. The obtained numerical results are compared with experimental and numerical ones found in the literature and reasonable agreement is obtained. Numerical investigations were carried out to evaluate the effects of the aspect ratios of the Rectangular Enclosure, A, and fins, A(f), on the heat transfer enhancement, by keeping the mass of the PCM and fins constant. Solutions are obtained for aspect ratios A (ranging from 3 to 8) and A(f) (ranging from 2.69 to 13.89). A comparative study of finned and unfinned Enclosures shows clearly that introducing fins weakens the undesirable natural convection, improves the nondimensional rate of heat extraction, and assures rapid solidification. Results indicate that for an aspect ratio A = 4 and in the range of the aspect ratio A(f) explored in this study, the nondimensional solidification time is reduced by 17.74%. The results also reveal that for a fin aspect ratio of A(f) = 5, the nondimensional solidification time is reduced by 49.48% when the aspect ratio of the Enclosure, A, varies from 3 to 8.
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computation of melting with natural convection inside a Rectangular Enclosure heated by discrete protruding heat sources
Applied Mathematical Modelling, 2013Co-Authors: El H Qarnia, A Draoui, El Khadir LakhalAbstract:Abstract This paper presents the results of a numerical investigation of the heat transfer by natural convection during the melting of a phase change material (PCM, n -eicosane with melting point of 36 °C) contained in a Rectangular Enclosure. This latest is heated by three discrete protruding heat sources (simulating electronic components) placed on one of its vertical walls. The power generated by heat sources is dissipated in PCM. The advantage of using this cooling scheme is that the PCMs are able to absorb high amount of heat generated by the heat sources, without acting the fan during the charging process (melting of the PCM). The thermal behavior and thermal performance of the proposed PCM based-heat sink are numerically investigated by developing a mathematical model based on the mass, momentum and energy conservation equations. The obtained numerical results show the impact of various key parameters on the cooling capacity of the PCM-based heat sink. Correlations encompassing a wide range of parameters were developed in terms of the dimensionless secured operating time (time required by one of the electronic components before reaching its critical temperature, T cr ∼ 75 °C) and the corresponding liquid fraction, using the asymptotic computational fluid dynamics (ACFD) technique.
Juanjuan Chang - One of the best experts on this subject based on the ideXlab platform.
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natural convection in a Rectangular Enclosure with sinusoidal temperature distributions on both side walls
Numerical Heat Transfer Part A-applications, 2008Co-Authors: Qihong Deng, Juanjuan ChangAbstract:A two-dimensional steady and laminar natural convection in an air-filled (Pr = 0.7) Rectangular Enclosure is investigated numerically. The horizontal walls are thermally insulated and the vertical side walls have two spatially varying sinusoidal temperature distributions of different amplitudes and phases. The governing equations in primitive variables are discretized by the finite-volume method and solved by the SIMPLE algorithm. The fluid flow and heat transfer characteristics are systematically investigated over a wide range of Rayleigh number (Ra = 103–106), amplitude ratio ( ), phase deviation (φ = 0 − π), and aspect ratio (Ar = 0.25–4). The results show that the natural-convection heat transfer in Enclosures with two sinusoidal temperature distributions on the side walls is superior to that with a single sinusoidal temperature profile on one side wall.
Yogesh Jaluria - One of the best experts on this subject based on the ideXlab platform.
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mixed convection from an isolated heat source in a Rectangular Enclosure
Numerical Heat Transfer Part A-applications, 1991Co-Authors: E Papanicolaou, Yogesh JaluriaAbstract:Abstract The mixed convection transport from an isolated thermal source, with a uniform surface heat flux input and located in a Rectangular Enclosure, is studied numerically. The Enclosure simulates a practical system such as an oven or an air-cooled electronic device, where an airstream flows through the openings on the two vertical walls. The heat source represents a heater or an electronic component located in such an Enclosure. The interaction of the cooling stream with the buoyancy-induced flow from the heat source is of interest in this work. Laminar, two-dimensional flow is assumed, and the problem lies in the mixed convection regime, governed by the buoyancy parameter GrIRe1 and the Reynolds number Re. Other significant variables include the locations of the heat source and the outflow opening. The inflow is kept at a fixed position. The mathematical model is developed with vorticity and stream function, along with temperature, as the dependent variables. The unsteady terms are retained in the vo...
Mohamed A Teamah - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of double diffusive mixed convective flow in Rectangular Enclosure with insulated moving lid
International Journal of Thermal Sciences, 2010Co-Authors: Mohamed A Teamah, Wael M ElmaghlanyAbstract:Abstract The present study is concerned with the mixed convection in a Rectangular lid-driven cavity under the combined buoyancy effects of thermal and mass diffusion. Double-diffusive convective flow in a Rectangular Enclosure with moving upper surface is studied numerically. Both upper and lower surfaces are being insulated and impermeable. Constant different temperatures and concentration are imposed along the vertical walls of the Enclosure, steady state laminar regime is considered. The transport equations for continuity, momentum, energy and spices transfer are solved. The numerical results are reported for the effect of Richardson number, Lewis number, and buoyancy ratio on the iso-contours of stream line, temperature, and concentration. In addition, the predicted results for both local and average Nusselt and Sherwood numbers are presented and discussed for various parametric conditions. This study was done for 0.1 ≤ Le ≤ 50 and Prandtl number Pr = 0.7. Through out the study the Grashof number and aspect ratio are kept constant at 10 4 and 2 respectively and −10 ≤ N ≤ 10, while Richardson number has been varied from 0.01 to 10 to simulate forced convection dominated flow, mixed convection and natural convection dominated flow.
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numerical simulation of double diffusive natural convection in Rectangular Enclosure in the presences of magnetic field and heat source
International Journal of Thermal Sciences, 2008Co-Authors: Mohamed A TeamahAbstract:Abstract Double-diffusive convective flow in a Rectangular Enclosure with the upper and lower surfaces being insulated and impermeable is studied numerically. Constant temperatures and concentration are imposed along the left and right walls of the Enclosure. In addition, a uniform magnetic field is applied in a horizontal direction. Laminar regime is considered under steady state condition. The transport equations for continuity, momentum, energy and spices transfer are solved. The numerical results are reported for the effect of thermal Rayleigh number, heat generation or absorption coefficient and the Hartmann number on the contours of streamline, temperature, and concentration as well as the dimensionless density. In addition, the predicted results for the average Nusselt and Sherwood numbers are presented and discussed for various parametric conditions. This study was done for constant aspect ratio A = 2 , Lewis number Le = 1 and Prandtl number Pr = 0.7 . The study covers ranges for 10 3 ⩽ Ra T ⩽ 10 6 , 0 ⩽ Ha ⩽ 200 , − 50 ⩽ ϕ ⩽ 25 and − 10 ⩽ N ⩽ 10 .