Residential air-source heat pump with refrigerant injection and variable speed compressor: Experimental investigation and compressor modeling

This paper presents an experimental study of a residential heat pump working with a variable speed scroll compressor with refrigerant injection and R410A as the working fluid. The experimental campaign is aimed at investigating the performance of the scroll compressor under different evaporating and condensing temperatures and rotational speeds. This campaign helped appropriate mathematical expressions to be chosen for an empirical compressor model that is presented in this study. Moreover, the impact of the superheat at the suction and injection ports is investigated for several compressor speeds and working conditions. Decreasing the evaporator superheat from 15 to 5K helped to increase the COP and heating capacity by 9.3% and 12.6% on average respectively, and to decrease the discharge temperature by 6K on average. Decreasing the injection superheat had no impact on the COP but helped to increase the heating capacity by 3.5% and decrease the discharge temperature by an additional 7K. The coupling of the injection and suction superheat control is also presented and offers perspectives for advanced expansion valve control of the injection cycle. Finally, an empirical model of the compressor is presented. This model is based on five dimensionless relations and shows good accuracy in predicting the compressor mass flow rates, electrical consumption and discharge temperature. (C) 2019 Elsevier Ltd and IIR. All rights reserved.