OPTIMAL CONFIGURATION AND THERMAL PERFORMANCE OF HEATED RECTANGULAR BLOCKS UNDER FORCED CONVECTION WITH VOLUME CONSTRAINTS Mujanayi Katumba J-M *,§ , Bello-Ochende T. ** and Meyer J.P. * * Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, 0002, South Africa, ** Department of Mechanical Engineering, University of Cape Town C ape Town, 7701 South Africa § Author for correspondence E-mail: jmarckatumba@gmail.com ABSTRACT This paper presents thermal management of heat transfer density rate from heated blocks mounted on a horizontal wall of a rectangular enclosure and subject to forced convection. The governing equations for mass, momentum and energy for laminar flow and convective heat transfer are solved in three-dimensions using a commercial Computational Fluids Dynamics (CFD) code. First numerical results validated with available experimental data showed that the rate of heat transfer increase with the Reynolds number. Thereafter a numerical optimization procedure is carried out in order to obtain the optimal blocks configuration that maximizes the heat transfer density rate and minimizes the peak temperature in the enclosure by selecting the sides of the blocks as design variables whilst the total volume is maintained constant. In term of the thermal performance of the heat transfer mechanism described by the dimensionless global conductance as well as by the overall Nusselt number, the results showed that optimal configurations were such that none of the blocks aspect ratio was equal to one. However thermal performance was much better when either the height-to-length ratio (B/G) or the height- to-width (B/C) ratio tends to its maximum. These optimal results obtained numerically are found to be fairly reliable. . INTRODUCTION Forced convection mechanism heat transfer has been widely used in both investigation and simulation of the cooling of electronic equipments or entities flush mounted or protruding on a wall as well as in a channel. In order to study the phenomenon of heat transfer from electronics, several works on cooling of heated elements by mixed convection in the laminar regime have been carried out by many authors using experimental procedure [1-7] or numerical analysis [8- 14]. From these studies results general characteristics of the cooling mechanism of heated elements were found in to be similar regarding the global thermal performance in accordance with the geometrical configuration of the heated elements. Numerical investigations were carried out in [15, 16] for forced convection in channel. The numerical results which agreed with experimental data proved that the slender-tall blocks enhanced the heat transfer compare with the flatter-short ones for low Reynolds numbers, less than 2000. Gradually as the years pass electronic entities are being condensed, miniaturized and concentrated on integrated circuits in electronics equipments to improve their functional performance (speed, memories etc)[17]. The miniaturization of heating element causes a considerable increase the heat flux rate within the element as the surface decrease while the generated heat increases causing the temperature of the heated element to raise drastically[18], therefore presents a high risk of overheating which definitely leads to the operational failure of the equipment as the main electronics components are designed to operate under a peak temperature value. On a thermal management point of view which aims for the maximization of heat removal in order to keep the element under an allowable temperature for functional reasons, forced convection was unable to reach proper cooling performance because of the excess heat generated. However, for reasons of power consumption, reliability, reasonable cost, air forced convection was found to be more advantageous from cooling methods for electronics equipment[18]. In order to prevent or to avoid limitations shown by air convection method, the need of optimization of some pertinent geometric parameters was inevitable to reach better cooling performance. That is how some researchers have begun to focus more on optimization studies of geometric parameters to improve the cooling mechanism in electronics equipments using different method. 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics 884