Conjugate natural convection from an array of discrete heat sources: Part 1 — Two- and three-dimensional model validation

1996 ◽  
Vol 37 (3) ◽  
pp. 231
Author(s):  
T.J. Heindel
Keyword(s):  
Natural Convection ◽  
Model Validation ◽  
Three Dimensional ◽  
Heat Sources ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Conjugate Natural Convection ◽  
Discrete Heat Sources

Laminar Natural Convection in a Discretely Heated Cavity: I—Assessment of Three-Dimensional Effects

1995 ◽  
Vol 117 (4) ◽  
pp. 902-909 ◽  
Author(s):  
T. J. Heindel ◽  
S. Ramadhyani ◽  
F. P. Incropera
Keyword(s):  
Natural Convection ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Companion Paper ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Laminar Natural Convection

Two and three-dimensional calculations have been performed for laminar natural convection induced by a 3 × 3 array of discrete heat sources flush-mounted to one vertical wall of a rectangular cavity whose opposite wall was isothermally cooled. Edge effects predicted by the three-dimensional model yielded local and average Nusselt numbers that exceeded those obtained from the two-dimensional model, as well as average surface temperatures that were smaller than the two-dimensional predictions. For heater aspect ratios Ahtr ≲ 3, average Nusselt numbers increased with decreasing Ahtr. However, for Ahtr ≳ 3, the two and three-dimensional predictions were within 5 percent of each other and results were approximately independent of Ahtr. In a companion paper (Heindel et al., 1995a), predictions are compared with experimental results and heat transfer correlations are developed.

The Effects of Side-Wall Conduction on Natural Convection in a Slot

1987 ◽  
Vol 109 (2) ◽  
pp. 419-426 ◽  
Author(s):  
G. D. Mallinson
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Radiation Effects ◽  
Three Dimensional ◽  
Side Wall ◽  
Thermal Coupling ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
High Prandtl Number ◽  
Side Walls

A numerical model for the interaction between natural convection in a slot and conduction in the side walls that are parallel to the plane of the slot is described. Two-dimensional equations containing source terms which account for the viscous and thermal coupling between the fluid and the walls are solved by a finite difference method. The model neglects radiation effects. Solutions for a slot of square cross section filled with a high Prandtl number fluid and heated from below are compared with the results of a Galerkin analysis made by Frick [8] and with solutions obtained by a fully three-dimensional model. Solutions for a slot filled with air and heated from the side are also validated by comparison with three-dimensional solutions. The data produced by the model predict that the more conventional Hele Shaw analysis overestimates heat transfer when the slot aspect ratio is greater than 0.05. Perfectly conducting walls are shown to reduce the rate of heat transfer by the fluid but to increase the strength of the flow. Some effects of walls that are neither adiabatic nor perfectly conducting are assessed.

Numerical investigation of Rayleigh-Benard Natural convection and entropy generation in a cubic cavity with discrete heat sources

2021 ◽  
pp. 1-9
Author(s):  
Chemseddine Maatki ◽  
Kaouther Ghachem ◽  
Mohammed A. Almeshaal ◽  
Nidhal Ben Khedher ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Entropy Generation ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Dimensional Distribution ◽  
Volume Method

Abstract The Three-dimensional natural convection with isothermal discrete heat sources in a cubical cavity has been carefully studied using the 3D vector potential-vorticity formulation. Based on the finite volume method, the governing equations are solved with a home-made computational code (written in Fortran). Assuming that all cavity vertical walls are adiabatic, the upper wall of the cavity is kept at a cold temperature. However, in the bottom face, heat sources are placed under different configurations. The size of the discrete sources, their positions, and their numbers are varied for different Rayleigh numbers. The Prandtl number is fixed at 0.71. Three-dimensional distribution of the temperature iso-surfaces, the heat transfer rate, and entropy generation are evaluated. It is found that heat transfer and entropy generation are strongly affected by the arrangement of the discrete heated sources. In conclusion, the heat transfer rate is maximized, and the entropy generation is minimized for the inline arrangement of more than two heaters compared to the diagonal one.

Geometrically-Accurate-Three-Dimensional Simulations of a Used Nuclear Fuel Canister Filled With Helium

2015 ◽  
Author(s):  
Triton Manzo ◽  
Mustafa-Hadj Nacer ◽  
Miles Greiner
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Ansys Fluent ◽  
Model Simulations

This paper presents preliminary results of heat transfer simulations performed in geometrically-accurate-three-dimensional model of nuclear fuel canister filled with helium. The numerical model represents a vertical canister, which relies on natural convection as its primary heat transfer mechanism, containing 24 PWR fuel assemblies. The model includes distinct regions for the fuel pellets, cladding and gas regions within each basket opening. Symmetry boundary conditions are employed so that only one-eighth of the package cross-section is included. The canister is assumed to be filled with helium at atmospheric pressure. A constant temperature of 101.7°C is employed on the canister outer surfaces, assuming the canister to be surrounded with water. These conditions of pressure and temperature were considered, in this paper, for comparison purpose with previous work. The effects of buoyancy-induced gas motion and natural convection, along with radiation and conduction through gas regions and solid are considered. Steady state simulations using ANSYS/Fluent were performed for different heat generation rates in the fuel regions. Simulations that include the effect of natural convection and others that do not include this effect are conducted. The peak cladding temperature and its radial and axial locations are reported. The maximum allowable heat generation that brings the cladding temperatures to the radial hydride formation limit (TRH=400°C) is also reported. The results of the three dimensional model simulations were compared to two dimensional model simulations for the same heat generation rate. The results showed that the two-dimensional simulations overestimate the temperature in the canister by almost 70°C.

Thermal Analysis of a Dynamic Lithium-Ion Battery during Charge

2012 ◽  
Vol 516-517 ◽  
pp. 489-493 ◽  
Author(s):  
Jia Qiang E ◽  
Yan Ping Long ◽  
Xiao Feng Hu ◽  
Rong Jia Zhu
Keyword(s):  
Lithium Ion Battery ◽  
Heat Generation ◽  
Electrochemical Reaction ◽  
Three Dimensional ◽  
Lithium Ion ◽  
Heat Sources ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Reaction Heat ◽  
Temperature Distributions

Four types of heat sources of a dynamic lithium-ion battery (LIB) during charge were studied, and temperature distributions inside the dynamic LIB caused by the four kinds of heat generation sources with different currents and temperatures during charge were simulated by using a electrochemical-thermal three-dimensional model. The ohmic heat is the largest heat resource with about 63.5% in the total heat generation during regular charge, the electrochemical reaction heat is dominant when the SOC is below around 10%, and the subsidiary reaction heat can not be ignored when the temperature in the battery is above 80°C. Current as well as ambient temperature plays a very important role in the overall thermal behaviors of the battery.

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