Evaporation heat transfer characteristics of R-245fa in a shell and plate heat exchanger for very-high-temperature heat pumps

A shell and plate heat exchanger (SPHE) has been introduced for use in very-high-temperature heat pumps (VHTHPs). However, studies on the evaporation heat transfer characteristics of refrigerants in SPHEs for use in VHTHPs are very limited. In this study, the evaporation heat transfer characteristics of R-245fa in the SPHE are measured and analyzed by varying the saturation temperature, mass flux, heat flux, mean vapor quality, and fluid direction. Experiments are conducted under high temperatures of 60−80 °C for VHTHP applications. The evaporation heat transfer coefficient increases as the mass flux and mean vapor quality increase, whereas it decreases as the heat flux increases. The two-phase frictional pressure drop increases as the mass flux and mean vapor quality increase. The heat transfer performance of the upward flow in the SPHE is better than that of the downward flow. In addition, empirical correlations of the Nusselt number and two-phase friction factor of R-245fa in the SPHE are derived.