Critical Heat Flux of Water at Subatmospheric Pressures in Microchannels

摘要

Critical heat flux conditions for water at subatmospheric pressures in an array of silicon-based, 227 μm hydraulic diameter, rectangular microchannels were experimentally studied. Experiments were conducted at exit pressures from 0.1 atm to 1 atm, mass fluxes from 86 kg/m~2 s to 303 kg/m~2 s, and an effective heat flux up to 444 W/cm~2. The annular flow pattern revealed during flow visualization and the high exit qualities at CHF conditions suggest dryout to be the CHF mechanism. An analysis, based on the experimental results and known CHF characteristics, on the dependency of the critical heat flux on various variables was performed. It was found that the boiling number at the CHF condition was approximately a constant.