Enhanced pool boiling on composite microstructured surfaces with microcavities on micro-pin-fins

Abstract

In the present study, five kinds of composite microstructured surfaces with different numbers of microcavities at the top of each micro-pin-fin were prepared. The effect of the number of microcavities at the top of the micro-pin-fins on the pool boiling performance in HFE-7100 was examined under different liquid subcooling degrees. The experimental results show that the wall superheats at the onset of nucleate boiling on the composite microstructured surfaces are almost around 0 K under different subcooling degrees, showing a tremendous drop in comparison with a micro-pin-fined surface (PF-30-60) and a smooth surface (SS). Compared with the heat transfer coefficients (HTC) of PF-30-60 and SS, the HTCs of the composite microstructured surfaces are increased significantly and this tendency becomes more pronounced with the increase of the number of microcavities. However, throughout the nucleate boiling region, PF-30-60-16 (i.e., the surface with 16 microcavities at the top of each micro-pin-fin) exhibits the best boiling heat transfer performance. The bubbles on the composite microstructured surfaces are mainly generated from the microcavities. Thereby, the bubble blockage during the liquid replenishment from the microchannels between the micro-pin-fins is relieved at high heat fluxes, leading to higher critical heat fluxes than those of PF-30-60 and SS.