Boiling binary mixtures at subatmospheric pressures

The authors present a study of 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 are unsuccessful in predicting the characteristics of aqueous mixtures. The significance of the results obtained to the use of binary coolants for electronics cooling applications is discussed