Heat transfer intensification in MEMS two-fluid parallel flow heat exchangers by embedding pin fins in microchannels

Abstract

This work proposes implementation of a passive heat transfer enhancement technique in MEMS two-fluid parallel flow heat exchangers as well as model based investigation of the same; the technique involves embedding square in-line pin-fins in the microchannels of the heat exchanger. Model based study is conducted using MEMS two-fluid heat exchangers, with and without pin fins, for a wide range of Reynolds number and two heat capacity ratios. With increase in Reynolds number, the effectiveness of heat exchangers with pin fins increases in comparison with those without pin fins for all heat capacity ratios; moreover, at low Reynolds number the effectiveness of both types of heat exchangers are equal. The power consumption in heat exchangers with pin-fins is higher than in those without pin-fins; the difference in the power consumption increases with increase in Reynolds number irrespective of the heat capacity ratio. This enhancement technique allows MEMS two-fluid parallel flow heat exchangers operate at higher throughput without compromising the effectiveness. For purposes of simulation, microchannel dimensions are kept at 150 μm (width) by 150 μm (height) by 2 cm (length) and pin fin dimensions are held at 75 μm (width) by 500 μm (pitch) while the Reynolds number is varied between 50 and 1500 for heat capacity ratios of unity and 0.5. For the cases considered for simulation, the maximum increase in effectiveness, relative to the baseline case, achieved is 84% and 66% for balanced and unbalanced flow conditions, respectively. • Square pin-fins embedded in microchannels for heat transfer enhancement of MEMS heat exchangers. • Simulations conducted for Reynolds number from 50 to 1500 and heat capacity ratios of 1 and 0.5. • High effectiveness possible without compromising flow rate and size and weight of heat exchanger. • Penalty of approach is increased pumping power.