Heat transfer and pressure drop in microchannels with isotropically etched pillars at sub-ambient temperatures

Abstract

Glass microfluidic devices are often manufactured using micromachining techniques that involve the use of wet etching. In applications where high-pressure fluids are used, the microchannels in the microchip are filled with pillar structures for mechanical strength. Owing to the isotropic nature of the wet etching process, the pillars resulting from this process are shaped as truncated cones. In this paper, we present the results of a numerical study for predicting the flow and the heat transfer characteristics in a microchannel with truncated cone-shaped pillar arrays at sub-ambient temperatures. In order to verify the developed correlations, we use Joule-Thomson microcoolers that contain a counter-flow heat exchanger (CFHX) as test platforms and operate these with nitrogen gas. The performance of the microcoolers predicted with the new correlations matches well with the experimental data. Using these correlations, the CFHX is optimized and the CFHX losses are reduced by more than 30%.