Boiling heat transfer with binary mixtures: Part I— A theoretical model for pool boiling

Abstract

Experimental evidence available in the literature indicates that the pool boiling heat transfer with binary mixtures is lower than the respective mole- or mass-fraction averaged value. Although a few investigators have presented analytical work to model this phenomenon, empirical methods and correlations are used extensively. In the present work, a theoretical analysis is presented to estimate the mixture effects on heat transfer. The ideal heat transfer coefficient used currently in the literature to represent the pool boiling heat transfer in the absence of mass diffusion effects is based on empirical considerations, and has no theoretical basis. In the present work, a new pseudo-single component heat transfer coefficient is introduced to account for the mixture property effects more accurately. The liquid composition and the interface temperature at the interface of a growing bubble are predicted analytically and their effect on the heat transfer is estimated. The present model is compared with the theoretical model of Calus and Leonidopoulos (1974), and two empirical models, Calus and Rice (1972) and Fujita et al. (1996). The present model is able to predict the heat transfer coefficients and their trends in azeotrope forming mixtures (benzene/ methanol, R-23/R-13 and R-22/R-12) as well as mixtures with widely varying boiling points (water/ethylene glycol and methanol/water).