Experimental validation of on-field measurement method for a heat pump system with internal heat exchanger.

Determining the on-field heating capacity and coefficient of performance (COP) of residential air-to-air heat pumps (HP) is problematic, given that measuring accurately the enthalpy and, specifically, the mass flow rate of air is challenging. This paper validates a promising on-field performance measurement method for HPs with an internal heat exchanger (IHX) as vapor injection system using experimental data obtained from air-to-water HP prototype in several operating conditions. The method is based on refrigerant fluid measurements and component energy/mass balances. Non-intrusive sensors, such as surface temperature sensors are used to estimate pressure and refrigerant mass flow rate in different types of HP systems, including air-to-air. Obtained results compared with intrusively measured reference values in steady-state conditions are in good agreement, suggesting that a comprehensive performance analysis can be conducted in already-installed high efficiency residential IHX air-to-water HPs, as well as IHX air-to-air HPs.