Numaerical Solution of Three Dimensionsl Conjugate Heat Transfer in a Microchannel Heat Sink and CFD Analysis

Abstract

In electronic equipments, thermal management is indispensable for its longevity and hence, it is one of the important topics of current research. The dissipation of heat is necessary for the proper functioning of these instruments. The heat is generated by the resistance encountered by electric current. This has been further hastened by the continued miniaturization of electronic systems which causes increase in the amount of heat generation per unit volume by many folds. Unless proper cooling arrangement is designed, the operating temperature exceeds permissible limit. As a consequence, chances of failure get increased.
Increasing circuit density is driving advanced cooling systems for the next generation microprocessors. Micro-Channel heat exchangers (MHE) in silicon substrates are one
method that is receiving considerable attention. These very fine channels in the heat exchanger provide greatly enhanced convective heat transfer rate and have been shown
to be able to meet the demands of the cooling challenge for the microprocessors for many generations to come.
This work focused on laminar flow (Re < 200) within rectangular micro-channel with hydraulic diameter 86μm for single-phase liquid flow. The influence of the thermophysical properties of the fluid on the flow and heat transfer, are investigated by evaluating thermo-physical properties at a reference bulk temperature. The micro-heat
sink model consists of a 10 mm long silicon substrate, with rectangular micro-channels,57μm wide and 180μm deep, fabricated along the entire length. Water at 293k is taken
as working fluid. The results indicate that thermo-physical properties of the liquid can significantly influence both the flow and heat transfer in the micro-channel. Assumption
of hydrodynamic, fully developed laminar flow is valid here on basis of Langhaar’s equation. The local heat transfer coefficient and averaged Nusselt number is calculated
and plotted for pressure drop of 50kpa, 30kpa and 10kpa. The result is verified for heat flux 50w/cm2, 90w/cm2 and 150w/cm . A three-dimensional Computational Fluid Dynamics (CFD) model was built using the commercial package, GAMBIT-FLUENT, to investigate the conjugate fluid flow and heat transfer phenomena