Effect of chevron angle on condensation heat transfer of HFC134a at high reduced pressures in plate heat exchangers

In industrial fields, heat source over 130°C are widely needed, and for this the development of industrial high-temperature heat pump systems has been promoted. For the heat release process in such the heat pump systems, the authors have studied on cooling heat transfer at supercritical pressures and condensation heat transfer at high subcritical pressures of refrigerants flowing in chevron-type plate heat exchangers (PHEs). In this study, to examine the effect of chevron angle on condensation heat transfer of HFC134a at high subcritical pressures, experiments were conducted using chevron PHEs with the chevron angles 30°, 47.5° and 65°. In the experiments, condensation heat transfer coefficients were obtained in the wide range of bulk fluid enthalpy comprising whole the saturated region, at the pressures of reduced pressures 0.65 and 0.80, and the mass flow rates of 7 and 11 kg/min. The condensation heat transfer coefficient increased with chevron angle, similarly with those at low subcritical pressures. The increment ratio of the condensation heat transfer coefficient against chevron angle was compared with that of condensation heat transfer coefficient from a conventional correlation developed based on low subcritical pressures data and that of cooling heat transfer coefficient at a supercritical pressure from experiments.