Demonstration of Computationally Efficient Vapor Injection Optimization Method for Spool Compressor

A heat pump is often considered a substitute for the conventional boiler due to its high efficiency. However, its performance is degraded when used in regions with extremely low outdoor temperatures. The refrigerant vapor injection technique is proven to improve the performance in refrigeration applications and it recently gained attention for heat pumping in cold climates. This article first develops a simplified approach to finding the equilibrium injection mass flow rate using a vapor compression cycle coupled with a mechanistic chamber model of a compressor. A novel spool compressor is then simulated with vapor injection for a wide range of operating conditions (−30  \(^\circ \) F to 35  \(^\circ \) F evaporator temperature and 110  \(^\circ \) F condenser temperature). The effect of the injection port diameter and its angular location is also evaluated. The compressor simulation model is based on the mechanistic chamber modeling approach and is validated using experimentally collected data for different refrigerants, operating conditions and cooling capacities. The preliminary results indicate the existence of an optimal injection port diameter of 0.4 in. and port location between 260 \(^\circ \) and 280 \(^\circ \) .