Analysis of CHF enhancement by magnetite nanoparticle deposition in the subcooled flow boiling region

Abstract

Subcooled flow boiling CHF experiments were conducted with DI water on bare stainless steel and nanoparticle-deposited surfaces under atmospheric pressure. Magnetite nanoparticles (Fe(3)0(4)) were evenly deposited on test sections by applying the same deposition process. The wettable surface was observed by the reduced contact angle and the porous and rough surface was identified by SEM image. Experiments were conducted over a mass flux range from 1000 kg/m(2)s to 5000 kg/m(2)s and with inlet temperatures of 40, 60, and 80 degrees C. The CHF enhancement was from 0% to 40% by the nanoparticle deposition. The CHF enhancement was increased as the mass flux increased, which lead to exit quality decrement. The trend of CHF enhancement was investigated using DNB mechanism and flow regime. The CHF enhancement of low mass flux in a slug flow was relatively lower than that of high mass flux in a vapor clot. The liquid sublayer dryout model and Kelvin-Helmholtz instability were used to evaluate the effect of the nanoparticle deposition on CHF enhancement. (C) 2017 Elsevier Ltd. All rights reserved.