C. Gururaja Rao

EFFECT OF SURFACE RADIATION ON CONJUGATE MIXED CONVECTION IN A VERTICAL CHANNEL WITH A DISCRETE HEAT SOURCE IN EACH WALL

Abstract The results of a numerical analysis of the problem of two-dimensional, steady, incompressible, conjugate, laminar, mixed convection with surface radiation in a vertical parallel-plate channel, provided with a flush-mounted, heat generating, discrete heat source in each wall, are presented here. Air, a radiatively non-participating medium, is used as the cooling agent. A computer code based on the finite volume method is written exclusively for solving the above problem. The effect of surface emissivity, aspect ratio, discrete heat source position and modified Richardson number on the fluid flow and heat transfer characteristics is explored. Useful correlations are evolved for the maximum temperature of the left and the right channel walls, the mean friction coefficient and the forced convection component of the mean friction coefficient.

Conjugate Mixed Convection With Surface Radiation From a Vertical Plate With a Discrete Heat Source

The results of a numerical study of the problem of two-dimensional, steady, incompressible, conjugate, laminar, mixed convection with surface radiation from a vertical plate with a flush-mounted discrete heat source are reported. The governing equations, written in vorticity-stream function form, are solved using a finite-volume based finite difference method. A hybrid grid system has been employed for discretization of the computational domain. The effects of (i) the magnitude and location of the heat source, (ii) the material and surface properties of the plate, and (iii) the free-stream velocity on both heat transfer and fluid flow have been studied. Based on a large set of (more than 550) numerical data, correlations have been developed for maximum and average non-dimensional plate temperatures and mean friction coefficient. A method for evaluating the forced convection mean friction coefficient component, which may be used in estimating the power input required for maintaining the flow, has been proposed

Interaction of Surface Radiation with Conduction and Convection from a Vertical Channel with Multiple Discrete Heat Sources in the Left Wall

This article reports the results of a numerical study of the problem of interaction of surface radiation with conduction and convection from a vertical channel equipped with three flush-mounted discrete heat sources in the left wall. The governing equations for temperature distribution along each of the two channel walls have been deduced based on appropriate energy balance between various energy interactions in which the channel is involved. Radiosity-irradiation formulation is employed to tackle radiation-related calculations, with the view factors involved therein obtained using Hottels crossed-string method. The governing nonlinear partial differential equations are converted into algebraic form through a finite-volume-based finite-difference method, and are subsequently solved using Gauss-Seidel iterative technique. An optimum grid system, with 26 grids along each of the three discrete heat sources and 11 grids along each of the two non-heat source portions of the board, is used for discretization of the computational domain. The effects of various pertinent parameters, viz., aspect ratio, volumetric heat generation, thermal conductivity, surface emissivity, and convection heat transfer coefficient, on temperature distribution along the left board, maximum temperature in the channel, and relative contributions of convection and surface radiation to heat dissipation from the channel are probed.

INTERACTION OF SURFACE RADIATION WITH CONJUGATE MIXED CONVECTION FROM A VERTICAL PLATE WITH MULTIPLE NONIDENTICAL DISCRETE HEAT SOURCES

Some of the important results of a numerical investigation into interaction of surface radiation with conjugate mixed convection from a discretely heated vertical plate with three nonidentical heat sources are provided here. The heat sources with identical rate of volumetric heat generation are placed flush-mounted along the plate in the descending order of their height from the bottom to the top ends of the plate. The heat sources are positioned at the leading edge, center, and the trailing edge of the plate, while the cooling medium considered is air, which is assumed to be radiatively transparent. The governing equations for fluid flow and heat transfer are initially converted into vorticity-stream function form and are later solved using the finite volume method coupled with Gauss-Seidel iterative solver. A computer code is written for the purpose. The effects of modified Richardson number, surface emissivity, and thermal conductivity on temperature distribution, peak temperature, drag coefficient, and relative contributions of mixed convection and radiation to heat dissipation are studied.

COMBINED CONDUCTION-MIXED CONVECTION-SURFACE RADIATION FROM A UNIFORMLY HEATED VERTICAL PLATE

The present article reports the results of a numerical study on combined conduction-mixed convection-surface radiation from a vertical plate with uniform internal heat generation. The study considers the governing fluid flow and heat transfer equations without boundary layer approximations. Air is taken to be the cooling medium. Stream function-vorticity formulation, coupled with finite volume method, is used to solve the problem. A computer code has been written for the purpose, and results are validated with available experimental and analytical results for asymptotic limiting cases. In addition to making comprehensive parametric studies, useful correlations for evaluating the nondimensional maximum and average temperatures of the plate and mean friction coefficient are deduced based on a large set of data generated from the code.

Simulation studies on multi-mode heat transfer from an open cavity with a flush-mounted discrete heat source

Prominent results of a simulation study on conjugate convection with surface radiation from an open cavity with a traversable flush mounted discrete heat source in the left wall are presented in this paper. The open cavity is considered to be of fixed height but with varying spacing between the legs. The position of the heat source is varied along the left leg of the cavity. The governing equations for temperature distribution along the cavity are obtained by making energy balance between heat generated, conducted, convected and radiated. Radiation terms are tackled using radiosity-irradiation formulation, while the view factors, therein, are evaluated using the crossed-string method of Hottel. The resulting non-linear partial differential equations are converted into algebraic form using finite difference formulation and are subsequently solved by Gauss–Seidel iterative technique. An optimum grid system comprising 111 grids along the legs of the cavity, with 30 grids in the heat source and 31 grids across the cavity has been used. The effects of various parameters, such as surface emissivity, convection heat transfer coefficient, aspect ratio and thermal conductivity on the important results, including local temperature distribution along the cavity, peak temperature in the left and right legs of the cavity and relative contributions of convection and radiation to heat dissipation in the cavity, are studied in great detail.

Parametric studies and correlations for combined conduction-mixed convection–radiation from a non-identically and discretely heated vertical plate

The present paper reports the parametric studies and correlations for the problem of combined conduction-mixed convection–radiation from a non-identically and discretely heated vertical plate. Three discrete heat sources of non-identical heights but with identical volumetric rate of heat generation are assumed to be flush-mounted in a thin vertical plate. The longest and the shortest heaters are provided at the leading and trailing edges of the plate, while the remaining heater is located centrally. The governing fluid flow and heat transfer equations are considered in their full strength without the boundary layer approximations and are solved using the finite volume method. A computer code is written to solve the problem and various parametric studies have been performed. The relative roles of free convection, forced convection and radiation in various fluid flow and heat transfer results have been elucidated. In conclusion, based on a large set of data generated from the code, correlations for maximum non-dimensional plate temperature, average non-dimensional plate temperature and mean friction coefficient have been evolved.