Experimental analysis of condensation of zeotropic mixtures from 70°C to 90°C in a plate heat exchanger

High temperature condensation is relevant for the heat pump system used for the district heating and the organic Rankine cycle system used for combined heat and power generation. By using a zeotropic mixture as working fluid in such systems, it is possible to achieve a higher system efficiency compared with those of pure fluids. Only two previous studies addressing zeotropic mixture high temperature condensation in plate heat exchangers are available in the open literature, and these studies considered ethanol/water mixtures. The current works present an experimental analysis of high temperature condensation of zeotropic mixtures in a plate heat exchanger. We analyzed the condensation of the hydrofluoroolefin mixture R1234ze(E)/R1233zd(E) and the hydrofluorocarbon mixture R134a/R245fa with different mass compositions at various condensation temperatures and mass fluxes. Based on the experimental results, we analyzed the temperature effects on the condensation heat transfer and identified a convective-dominated condensation heat transfer process. Furthermore, the results suggest that the mixture R1234ze(E)/R1233zd(E) has the up to 8.5 % and 4.4 % higher heat transfer coefficient and frictional pressure drop, respectively, than the R134a/R245fa mixture. A modified Silver-Bell-Ghaly model predicted the heat transfer data with a 7.1 % mean absolute percentage deviation between the predicted and experimental results, and a new pressure drop correlation developed using the mixture test data predicted the pressure drop results with a 6.2 % mean absolute percentage deviation.