Dimensional Optimization of Two-Phase Flow Boiling in Microchannel Heat Sinks

Abstract

The heat transfer coefficient (HTC) of microchannel heat sinks (MHS) is higher than common heat sinks due to higher area to volume ratio. Its value for two-phase flow boiling is much superior to single-phase flow. In addition, the two-phase flow boiling provides uniform wall temperature close to the coolant’s saturation temperature in low vapor qualities. In the present study, a heat sink is optimized dimensionally after modeling of the boiling of R134a refrigerant in the microchannels. Firstly, mixture two-phase method along with the wall heat flux partitioning are utilized to introduce an applied thermal model to design MHSs. The heat sink mounted on the backside of an Intel core i7-900 desktop processor with dimensions of 19 mm×14.4 mm× 1 mm is numerically simulated to investigate the thermal performance. The HTC and the exit vapor quality are comparable with the available empirical correlations and first law of thermodynamics, respectively. Then the proposed model is developed to optimize the dimensions of the microchannels to design the heat sink with minimized wall temperature. Bound optimization by quadratic approximation (BOBYQA) method results in the optimized dimensions of the microchannels in the heat sink. Optimization of heat sink’s geometry in terms of the dimensions of the microchannels at various boundary conditions will be practical as the unique application of the model.