Comparative evaluation of the evaporation heat transfer characteristics of a low-GWP refrigerant R-1234ze(E) between shell-and-plate and plate heat exchangers

In this study, the evaporation heat transfer characteristics of R-1234ze(E) in a shell-and-plate heat exchanger (SPHE) and plate heat exchanger (PHE) are measured and analyzed by varying the mass flux, saturation temperature, heat flux, and vapor quality. The evaporation heat transfer coefficients of the SPHE and PHE are highly affected by the mass flux, but are hardly influenced by the saturation temperature. The evaporation heat transfer coefficient of the PHE decreases rapidly at high vapor qualities due to dry-out, while that of the SPHE remains constant even at high vapor qualities due to a large liquid pool. The two-phase frictional pressure drops in the SPHE and PHE are strongly influenced by the mass flux and saturation temperature. In addition, the heat transfer characteristics of R-1234ze(E) in the SPHE and PHE are compared in terms of the enhancement and penalty factors. Furthermore, empirical correlations of the Nusselt number and two-phase friction factor are developed using dimensionless parameters.