Investigation of mixed convection heat transfer from a rectanguler cross-section channel with discrete heat sources at the top and at the bottom

Ill INVESTIGATION OF MIXED CONVECTION HEAT TRANSFER FROM A RECTANGULAR CROSS-SECTION CHANNEL WITH DISCRETE HEAT SOURCES AT THE TOP AND AT THE BOTTOM (Ph. D. Thesis) Ayla DO?AN GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY October 2003 ABSTRACT In this study, the mixed convection heat transfer has been investigated experimentally and numerically under steady-flow conditions for the laminar flow in a horizontal channel with heat dissipating chips representing electronic components. Experimental studies were carried out for five different aspect ratios (W/H), various Reynolds numbers and different heat fluxes. The results obtained by using a numerical method have been compared with experimental results. PHOENICS package program has been used for the numerical studies. In both experimental and numerical studies, row-averaged Nusselt number distributions and the effect of Grashof and Reynolds number on the buoyancy- driven secondary flow have been investigated. Distributions of velocity vectors and temperature contours have been determined by the numerical method and the results have been presented in detail. The results show that with decreasing W/H ratio, the effect of free convection plays a more important role and causes the mixed convection heat transfer. Specifically, at high Reynols numbers, the strength of the buoyancy-driven secondary flow is smaller. The effect of forced convection increases and the point for which Nusselt number starts to increasing moves towards the first rows of heaters relative to the channel lengthIV with increasing W/H ratio. It is determined that the effect of mixed convection is more inportant for W/H=4. Science code :962 Key words : Discrete heat sources, channel flow, mixed convection Page number : 172 Adviser : Prof. Dr. Mecit SİVRİO?LU