Effect of structural parameters on pool boiling heat transfer for porous interconnected microchannel nets

Abstract

Porous interconnected microchannel nets were developed using microfabrication techniques for pool boiling heat transfer enhancement with both subcooled and saturated deionized water as working fluid at atmospheric pressure. The effects of varying the powder morphology, powder size and channel width on the pool boiling heat transfer were studied. Experimental results showed that these structures exhibited a lower wall-superheat at the onset of nucleate boiling (ONB) and a higher nucleate boiling heat transfer coefficient (HTC) than the solid interconnected microchannel net. The sample of medium size powders (50–75μm) yielded a maximum heat transfer coefficient while the powder morphology has little influence on the boiling heat transfer performance. At the low heat flux, the HTC was found to increase with decrease of the channel width while at the high heat flux, a reverse trend was observed. High speed visualization (2000 frames/s) revealed that the bubble growth was governed by the heat transfer regime at qa=225kW/m2 and no waiting phase was observed due to the overlap of the next bubble expulsion in the same vertical channel.