Experimental flow boiling characteristics of R134a/R245fa mixture inside smooth horizontal tube

The flow boiling characteristics were experimentally studied in smooth horizontal tube for pure R245fa and one of its mixtures, R134a/R245fa with 0.82/0.18 in mass fraction, which was regarded as a promising working fluid for Organic Rankine Cycle (ORC). The flow boiling heat transfer coefficient and pressure drop for the two fluids were measured under different vapor quality, mass flux, tube wall heat flux and evaporating pressure. Correlation for predicting the flow boiling heat transfer coefficient was developed for the selected mixture based on the experimental data. The results indicated that the flow boiling heat transfer coefficients of the two working fluids went up with mass flux, heat flux and evaporating pressure under the experimental conditions. The mixture of R134a/R245fa with 0.82/0.18 in mass fraction had less pressure drop, but higher heat transfer coefficient than that of the pure R245fa. The absolute errors of 89% experimental data are within 10% of prediction of the present developed correlation for the mixture. The results may benefit the potential utilization of R134a/R245fa in ORC. (C) 2016 Elsevier Ltd. All rights reserved.