Analytical Study on the Performance Characteristics of a Liquid Injection Refrigeration Cycle

A residential heat pump faced with reliability problems due to high compressor discharge temperature and lower performance at lower ambient temperatures. Many researchers have been trying to overcome this problem by applying vapor injection techniques. However, the application of the vapor injection cycle caused higher cost due to the increased components such as internal heat exchanger or flash tank. Liquid injection technique has merits of cost and cycle reliability due to refrigerant that discharged from the condenser was expanded and injected directly into the compressor. In this study, a simulation program for a liquid injection heat pump cycle was developed. The performance of the cycle was simulated using a mass and energy balances. The model was validated by comparing the predictions with measured data at various operating conditions. Based on the simulation results, cycle performance characteristics were discussed at various operating and compressor design conditions using the simulation program.