The results of an experimental investigation of pool boiling of water at subatmospheric pressures from small horizontal heat sources are reported. The heat sources are upward-facing copper surfaces submerged in a laterally-confined, finite pool of liquid. The saturated pool boiling heat transfer characteristics and the critical heat flux (CHF) condition were determined in the experiments. Low pressure boiling of saturated water provides a means of removing heat at high heat flux levels while maintaining low surface temperatures. However, at heat flux levels up to about 60 2 W/cm the frequency of bubble departure at low pressure is much less than the frequency of bubble departure at higher pressure (atmospheric). With low pressure boiling, only one or two very large bubbles form cyclically on the small heated surface, during the boiling process. This intermittent process may result in large, undesirable temperature oscillations at the heated surface for low pressure boiling. High-frequ...

This study considers boiling binary mixtures of water with methanol or 2-propanol at subatmospheric pressures. Liquid-phase equilibrium vapor pressures, binary phase equilibrium thermodynamic properties, heat transfer characteristics, and the critical heat flux (CHF) condition are determined for saturated pool boiling from a localized heat source while varying the concentrations of methanol and 2-propanol in water. The heat source is an upward-facing copper surface submerged in a laterally-confined, finite pool. Low pressure boiling of aqueous mixtures provides a means of removing high heat fluxes while maintaining low surface temperatures. Small additions of alcohol to water increase the CHF condition above that of pure water. Higher concentrations of alcohol begin decreasing the CHF condition to that of the pure alcohol. While single-component correlations using mole weighted binary liquid thermodynamic properties have been shown to predict ideal binary mixture boiling behavior, they...