Evaluation of a Novel Enhanced Boiling Surface in Cryogenic Liquids

Abstract

Experimental results of saturated nucleate pool boiling on a novel enhanced boiling surface in liquid oxygen, liquid nitrogen, liquid argon and Freon-12 are reported. Measurements of heat transfer coefficient as a function of coating thickness are also presented. The enhanced surface used was a metallic porous coating which is shown to have excellent heat transfer characteristics. The efficiency of the surface is shown to depend on the liquid properties at low heat fluxes (q<lWcm⁻²) and on the coating thickness at higher heat fluxes. Three regions are identified within the boiling curve and the heat transfer mechanisms associated with each region are discussed. At low heat flux it is suggested that boiling occurs within the porous coating with vapour removal via well defined channels. At high flux boiling is confined to the surface of the coating and the thermal conductivity of the coating dominates the heat transfer.