Geometric Optimization of Complex Heat Exchangers using Constructal Technique

Abstract

The application of microchannel heat exchangers for cooling is documented in this study. Numerical optimization is carried out with the goal of minimising the peak wall temperature in the microchannel heat sink modelled with solid and half hollow square micro fins. A high-density heat flux q'' from a microelectronic device was applied at the bottom wall of the microchannel heat sink with circular flow channel embedded in a highly conductive rectangular block aluminium substrate. Single phase water was used as coolant to remove the deposited heat at the internal channel walls and in the internal surfaces of half hollow square fins, while cool air stream flows externally over the vertical fins in a forced convection laminar regime to take away the excess heat on the micro square fins. Computational Fluid Dynamics (CFD) code was employed to descretised and solve the governing equations. The results of numerical optimization showed that the combined microchannels with solid square fins has the highest global thermal conductance than the microchannel with half hollow square fins. The limiting case of a single microchannel heat sink without fins agrees with what is in open literature.