Volume 2: Innovative Solutions for Energy Transitions: Part I

A Comparative Study on Pool Boiling of Fc-72 on Micro-Pin-Fin Silicon Surfaces With and Without Nanoparticles Zhen Cao , Bin Liu , Zan Wu , Yonghai Zhang , Jinjia Wei , Bengt Sunden*

Abstract

Several methods have been developed to enhance boiling heat transfer by surface modification, e.g., mechanical methods, chemical methods and hybrid methods. In the present study, micro-pin-fin silicon surfaces are prepared by a dry etching method. Subsequently, the micro-pin-fin surfaces are deposited with copper nanoparticles (20±5 nm) by an electrostatic deposition method. Saturated pool boiling heat transfer of FC-72 is experimentally investigated, illustrating the effect of nanoparticles on the saturated pool boiling heat transfer. Compared with the micro-pin-fin surface, the nanoparticles have slight effects on the heat transfer at low heat fluxes (< 5 W/cm2 ), while at moderate-high heat fluxes (>5 W/cm2 ), the effect of nanoparticles depends on the deposition time. In the present case, heat transfer is deteriorated on the micro-pin-fin surface with 1h deposition at moderate-high heat fluxes, but the heat transfer is slightly enhanced at moderate heat fluxes (5 – 15 W/cm2 ) and is slightly deteriorated at high heat fluxes (>15 W/cm2 ) on the micro-pin-fin surface with 2h deposition. Additionally, compared with the micro-pinfin surface, the critical heat flux (CHF) is slightly enhanced (around 7%) on the micro-pin-fin surface with 2h deposition, but is almost the same on the micro-pin-fin surface with 1h deposition. To study the reasons behind these results, SEM images are taken to characterize the surfaces and high speed visualization is conducted to compare bubble behaviors. In addition, supplementary experiments are designed to measure the wickabiltiy on these surfaces.

Keywords pool boiling, nanoparticle, critical heat flux, heat transfer