Simulation and experimental investigation on performance of heat pump scroll compressor with two-phase vapor injection

Vapor injection enthalpy-enhanced technology is key to addressing the issues of heating capacity degradation and energy efficiency reduction in heat pumps under low-temperature conditions. Against this backdrop, this paper focuses on resolving the challenge of excessively elevated discharge temperatures in heat pump systems during low-temperature operation. A thermodynamic model is constructed to analyze the influence of vapor injection parameters in superheated and two-phase states on compressor performance. An experimental platform for vapor injection scroll compressors was built. The vapor injection state was regulated using electric heaters, and the system performance under different refrigerant injection state levels was compared and analyzed. This study shows that during superheated vapor injection, with the increase of injection temperature, the main branch flow rate, total mass flow rate, and heating capacity slightly decrease, while the coefficient of performance (COP) increases. During two-phase vapor injection, with the increase of injection quality, the injection mass flow rate increased by 55.87% within the injection quality range of 60%–90%, and the heating capacity increases by 3.72%. Compared with the experimental data, the simulation errors of the two types of vapor injection are controlled within 10% respectively. Additionally, the injection point near the suction chamber enhances mass flow rate and heating capacity but increases power consumption and lowers COP, while the injection point near discharge chamber yields opposite trends. Based on these findings, injection strategies for different application scenarios are also proposed.