Optimizing microchannel heat sink performance: Effect of step-gap design and contraction on flow boiling stability and heat transfer

Abstract

Liquid cooling with cold plates (microchannels) is an advanced thermal management technique used in high-performance electronics and computing systems. Conventional microchannels have a straight fin array that shows instabilities during two-phase flow boiling. The present experimental investigation continues previous studies to explore the effects of combining the contraction before the microchannels (CBM) and a step gap above the microchannels (SGAM) in the enclosed cover of the heat sink to improve two-phase convective boiling performance. The microchannel heat sink is sized at 49 mm × 52 mm, featuring a channel width of 200 μm and a height of 3 mm, with a fin thickness of 200 μm. Dielectric fluid HFE-7000 was used as the working fluid, and the mass flux ranges from 30 to 260 kg/m2·s, with concentrated heat flux varying from 50 to 156 W/cm2. The results reveal that the combination configuration significantly reduces pressure drop by approximately 23–56 % lower than that of the plain (Conventional) configuration. This combination of configurations is especially effective at a high heat flux above 100 W/cm2. Experimental results indicate that the combination configuration lowers wall superheat temperatures compared to the plain sample, therefore enhancing the overall heat transfer coefficient by 30–154 % across the tested mass flux range. These findings underscore the potential of combining contraction before microchannels (CBM) and step gap above microchannels (SGAM) configurations to significantly enhance flow boiling stability and heat transfer performance while incurring a much lower pressure drop penalty.