Experimental study on single bubble growth of R32+R1234yf binary mixtures during saturated pool boiling

R32 + R1234yf mixtures are considered highly promising refrigerants. Understanding the bubble growth characteristics of mixtures is vital for understanding their boiling heat-transfer performance. In this study, pool boiling experiments were conducted to investigate the single-bubble growth characteristics of R32, R1234yf, and their binary mixtures. The bubble growth curves for each test refrigerant were obtained in the superheat range of 1.3-6.2 K. The results showed that the asymptotic bubble growth rates of the pure refrigerants were slower than those predicted using previous theoretical models, which were developed for isolated bubbles growing in an infinite superheated liquid. The bubble growth constants of the mixtures were lower than those of the pure components, whereas the growth exponents were greater than the "ideal growth exponent." The sudden decrease in the effective wall superheat and sharp increase in mass transfer resistance slowed the initial bubble growth rate. In the late stage of growth, the microlayer that had not yet dried out provided stable heat input to the bubble, resulting in a higher asymptotic growth rate than that of pure components. A set of dimensionless correlations for the bubble growth rate of mixtures is proposed, and they predicted the data in this study within a +/- 15% deviation band.