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ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
A NUMERICAL STUDY OF THE NATURAL CONVECTIVE HEAT TRANSFER FROM THE SURFACE OF A THIN HORIZONTAL PLATE HAVING A WAVY SURFACE WITH VARIABLE HEIGHT
Submission Author:
Santiago del Rio Oliveira , SP
Co-Authors:
Santiago del Rio Oliveira
Presenter: Santiago del Rio Oliveira
doi://10.26678/ABCM.ENCIT2018.CIT18-0076
Abstract
A numerical study of natural convective heat transfer from a thin, one-sided, two-dimensional horizontal plate having a uniform surface temperature has been undertaken. The surface shape is wavy, and attention has been given to both the case where the surface waves have a triangular shape with variable height and to the case where the surface waves have a rectangular shape with variable height. Three profiles were considered for the variable height: linear, parabolic and exponential. The temperature of the plate surface is higher than the temperature of the surrounding fluid. While there have been some limited previous studies of natural convective heat transfer from thin, one-sided horizontal plates, these studies have mainly considered only the case where the plate is flat (non-wavy) and where the flow over the plate is laminar. Here, the conditions considered are such that laminar flow, transitional flow and turbulent flow can occur over the plate. The flow has been assumed to be two-dimensional 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 wave surface has been expressed in terms of a mean Nusselt number based on the plate width. The Nusselt number is dependent on the Rayleigh number, on the Prandtl number and on the width of the plate. 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 wave surface and of the local Nusselt number for the wave surface have been considered. Results for a wide range of dimensionless surface wave profiles for both triangular and rectangular surface waves have been obtained and used to determine which profile produces the best layout enhancement in the natural convective heat transfer rate compared to that from a plane (non-wavy) horizontal surface.
Keywords
Natural Convection, wavy surface, triangular waves, rectangular waves, \variable height
