BOILING HEAT-TRANSFER WITH BINARY-MIXTURES - PART-I - THEORETICAL-MODEL FOR POOL BOILING

Experimental evidence available in the literature indicates that the p ool boiling heat transfer with binary mixtures is lower than the respe ctive mole- or mass-fraction-averaged value. Although a few investigat ors 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 wed currently in th e literature to represent the pool boiling hear transfer in the absenc e of mass diffusion effects is bused on empirical considerations, and has no theoretical basis. In the present work, a new pseudo-single com ponent heat transfer coefficient is introduced to account for the mixt ure property effects more accurately. The liquid composition and the i nterface temperature at the interface of a growing bubble are predicte d analytically and their effect on the heat transfer is estimated. The present model is compared with the theoretical model of Calus and Leo nidopoulos (1974), and two empirical models, Calus and Rice (1972) and Fujita et al. (1996). The present model is able to predict the heat t ransfer coefficients and their trends in azeotrope forming mixtures (b enzene/methanol, R-23/R-13 and R-22/R-12) as well as mixtures with wid ely varying boiling points (water/ethylene glycol and methanol/water).