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ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
A NUMERICAL STUDY OF THE SIMULTANEOUS NATURAL CONVECTIVE HEAT TRANSFER FROM THE TOP AND BOTTOM SURFACES OF A THIN HORIZONTAL CIRCULAR DISK IMBEDDED IN AN ADIABATIC CONCENTRIC DISK
Submission Author:
Santiago del Rio Oliveira , SP
Co-Authors:
Santiago del Rio Oliveira
Presenter: Santiago del Rio Oliveira
doi://10.26678/ABCM.ENCIT2018.CIT18-0077
Abstract
A numerical study of natural convective heat transfer from a thin, two-sided, horizontal circular disk having a uniform surface temperature imbedded in an adiabatic concentric disk has been undertaken. Attention has been given to the effects of the size of the adiabatic concentric disk relative to the diameter of the heated circular diameter on the natural convective heat transfer rate from the top and bottom surfaces of the circular heated disk and on the total heat transfer rate from the heated circular surface. The temperature of the top and bottom surfaces are higher than the temperature of the surrounding fluid. While there have been previous studies of natural convective heat transfer from thin, two-sided horizontal circular disks, these studies have only considered the case where the circular disk is not imbedded in an adiabatic concentric disk. The conditions considered in the present study are such that laminar flow, transitional flow and turbulent flow can occur over the circular disk. The flow around the entire circular disk has been considered and the heat transfer from the top and bottom surfaces of the disk have been studied. The flow has been assumed axisymmetric and steady and the Boussinesq approach has been adopted. The k¬-epsilon turbulence model has been used with full account being taken of buoyancy force effects. This turbulence model was applied under all conditions considered. The commercial CFD solver ANSYS FLUENT© has been used to obtain the solution. The mean heat transfer rate from the top and bottom surfaces of the circular disk has been expressed in terms of a mean Nusselt numbers based on the circular disk diameter. These Nusselt numbers are dependent on the Rayleigh number, on the Prandtl number and on the relative size of the adiabatic concentric disk. Results have been obtained only for a Prandtl number of 0.74, i.e., essentially the value for air. Values of the mean Nusselt number averaged over the top and bottom surfaces of the circular disk have been considered. Results have been obtained for a wide range of adiabatic concentric disk relative sizes and used to determine what is its influence on the natural convective heat transfer rates from the top and bottom surfaces of the circular disk and on the total heat transfer rate from this disk.
Keywords
Natural Convection, circular disk, adiabatic edge, k-epsilon turbulence model
