Effects of coating structure by A1203 nanoparticles deposition on critical heat flux Of R123 in flow boiling

Abstract

In this study, R-123 flow boiling experiments were carried out to investigate the effects of nanoparticle deposition on heater surfaces on flow CHF and boiling heat transfer. It is known that CHF enhancement by nanoparticles results from porous structures. Although previous studies have investigated the surface effects through surface modifications, most studies are limited to pool boiling conditions and so the porous effects in flow boiling heat transfer are still unclear. This paper focused on the porous effects on CHF in flow boiling. In this study R123 was used to investigate the CHF and boiling mechanisms. Bare and A1203 nanoparticles-coated surfaces were prepared for the experiments. The CHF of each surface was measured with different mass fluxes of 1600, 1800, 2100, 2400 and 2600 kg/m2s. The nanoparticles- coated tube showed CHF enhancement up to 17% at 2400 kg/m2s mass fluxes compared to the bare tube. The factors for CHF enhancement are related to the enhanced rewetting process derived from capillary action through porous structures built-up by nanoparticles suppressing wettability since highly wettable R123 refrigerant was used as a working fluid.