Enhance flow boiling in Tesla-type microchannels by inhibiting two-phase backflow

Abstract

Improving CHF and HTC of microchannel flow boiling is highly desirable for high-power density electronics cooling. However, two-phase flow instabilities strongly influence the enhancement of flow boiling in confined domains. Although extensive surface modifications and advanced functional structures have significant effects on two-phase heat transfer, gradual suppression of vapor backflow along in the entire channel length still lacks. A novel tesla-type copper microchannel configuration was explored with aim to inhibit vapor backflow and promote two-phase transport simultaneously in the forward direction in this work. Also, the effect of this configuration on two-phase mixing is investigated in the backward direction. Experiments are conducted on DI-water with mass velocity varying from 60 to 360 kgm−2s−1. Flow boiling and two-phase regimes are comprehensively investigated and compared to plain-wall microchannel. Overall HTC and CHF are significantly increased owing to effective suppression of vapor backflow in forward direction and enhanced two-phase mixing in backward direction. For example, at G = 360 kgm−2s−1, CHF and HTC are up to 274 Wcm−2 and 144 kWm−2K−1, respectively, accompanying with enhancements of 88.4% and 86.8% in the forward direction. Interestingly, the thermal performances in the forward direction outperform that in backward direction as the further increase of mass velocities, indicating the successful regulation of backflow. Upon the management of vapor backflow, two-phase flow instability regarding pressure fluctuation is dramatically reduced up to 7-fold.