Experimental study on flow boiling in ultrahigh-aspect-ratio copper microchannel heat sink

One ultrahigh-aspect-ratio copper microchannel heat sink (AR = 25) was fabricated with wire electrical discharge machining technique, in which the flow boiling heat transfer of deionized water was experimentally investigated. The results show the present heat sink has a superior performance in the critical heat flux and a low thermal resistance compared to other ones (AR = 1, 5 and 15), even though its mass flux is around ten times lower than that in regular one (AR = 1). The largest improvement of critical heat flux and the maximum difference of thermal resistance are 40.95 % and 40.28 %, respectively, for the ultrahigh-aspect-ratio channel compared to those for the channel with AR = 1. It is found that the nucleate bubbles between the elongated bubbles can make full use of the remaining heat transfer area of the ultrahigh-aspect-ratio microchannel, which significantly improves its flow boiling thermal performance at a low heat flux. At a high heat flux, the nucleate bubbles generated in the deformed liquid film enhance the evaporative heat transfer process. The coexisting heat transfer mode in the ultrahigh-aspect-ratio microchannel can prolong the nucleate boiling period, which contributes to the heat transfer enhancement of the present heat sink.

Automated summary

In this study, an ultrahigh-aspect-ratio copper microchannel heat sink was fabricated using wire electrical discharge machining technique, and the flow boiling heat transfer of deionized water was experimentally investigated. The results showed that compared to heat sinks with aspect ratios of 1, 5, and 15, the present heat sink exhibited superior performance in critical heat flux and thermal resistance, despite having a much lower mass flux. The ultrahigh-aspect-ratio channel demonstrated a significant improvement in critical heat flux and thermal resistance, attributed to the utilization of nucleate bubbles and coexisting heat transfer modes.