Performance comparison among two-phase, liquid, and vapor injection heat pumps with a scroll compressor using R410A

Although two-phase injection technique is expected to improve the performance and reliability of heat pumps in cold climate conditions, its application is limited due to wet-compression. In this study, a numerical model was developed and validated to predict the performance of liquid, vapor, and two-phase injection heat pumps. The performance characteristics of the liquid, vapor, and two-phase injection heat pumps with a scroll compressor using R410A were compared with the others, based on the predicted data. The optimum injection quality in the two-phase injection heat pump to achieve maximum COP was analyzed as a function of the injection pressure, compressor frequency, and outdoor temperature. The two-phase injection heat pump with the optimum injection quality exhibited the highest COP among all injection types with a proper discharge temperature. In addition, the two-phase injection heat pump with the optimum injection quality was more effective in COP improvement with decreasing outdoor temperature.