Simulations on the performance of a vapor-injection heat pump for different cylinder volume ratios of a twin rotary compressor

In residential air-source heat pump systems, the refrigerant injection technique has rapidly developed in recent years due to its outstanding performance at low ambient temperatures. A numerical simulation model of a flash tank vapor-injection heat pump with a twin rotary compressor is newly presented in this paper. The performance of the twin rotary compressor with refrigerant injection was simulated using a loss and efficiency model. The model was validated by comparing the predictions with measured data. In addition, the model was used to analyze the performance characteristics of the vapor-injection heat pump according to the cylinder volume ratio of the twin rotary compressor. Based on the simulation results, optimum cylinder volume ratios were suggested for various design conditions, including for the fixed first cylinder volume, the fixed total cylinder volume, and the fixed heating capacity.