Research PaperNumerical study of the effects of injection-port design on the heating performance of an R134a heat pump with vapor injection used in electric vehicles

- A simulation model for an EV heat pump with vapor injection is developed and validated.
- Geometries of the injection port are analyzed according to angle of the injection port.
- Design of the injection port is determined to optimize COP and isentropic efficiency.
- Performance of dual-injection ports is compared to that of the non-injection heat pump.

Heat pumps, which enable the cooling and heating of vehicular cabins, consume a significant portion of the total energy consumption in electric vehicles (EVs). The efficiency of the heat pump is typically degraded owing to cold-weather conditions, so the refrigerant-injection technique has been proposed for improving the system performance and compressor reliability. In this study, a simulation model for an R134a heat pump with vapor injection is developed and validated by performing thermodynamic analyses with geometrical information. The effects of the injection-port design are investigated using the developed numerical model. Single-injection and dual-injection ports are considered to optimize the coefficient of performance (COP) and isentropic efficiency by controlling the injection mass flow rate. The optimal angles of the single- and dual-injection ports are determined to be 440° and 535°/355° (for pocket A/B), respectively, while the corresponding COPs are improved by 7.5% and 9.8%, respectively, compared to the non-injection heat pump at an outdoor temperature of −10 °C.