Experimental Investigation of Critical Heat Flux Enhancement by Micro/Nanoscale Surface Modification in Pool Boiling

Nanofluids, which contain uniformly and stably dispersed nanoparticles, exhibit an abnormal enhancement of the critical heat flux (CHF) when used as a working fluid in pool boiling. It has recently been demonstrated that optimal CHF enhancement in nanofluids is attained by the significant deposition of nanoparticles on the heater surface during pool boiling. The surface deposition of oxidized metal nanoparticles significantly enhances the wettability, and fractal micro/nanostructures formed by nanoparticle deposition induce liquid suction due to capillary wicking. It is supposed that the superior wettability and capillary wicking of the nanoparticle-fouled surface enhances CHF by promoting the dry patches to be effectively rewetted during the boiling process. In this regard, the excellent CHF performance of the nanoparticle-deposited surface can be reproduced using artificial structures via innovative surface-modification methods that yield good wettability and capillarity. To accomplish this goal, we plan to design and fabricate various artificial micro/nano-structured surfaces with good surface wettability and capillarity, and investigate their CHF performance. In the present study, we examined experimentally the CHF performances of a series of surface-modified samples (plane, micro-structured, nano-structured, and micro/nano structured surfaces). Pool boiling heat transfer of pure water on sample surfaces was investigated under atmospheric conditions. The CHF increase due to artificial surface modification is discussed based on solid-liquid interfacial parameters (static contact angle, roughness) that are closely related to CHF phenomenon in pool boiling.