18 May 2017
Estimating the performances of air-to-air heat pumps (HPs) on-field is problematic given that measuring accurately the enthalpy and mass flow rate of air is challenging. A method based on the compressor energy balance can be used to estimate the coefficient of performance (COP) of different HP types, including air-to-air, on-field. In this method heat transfer from the compressor shell towards the ambient air must be evaluated. In this paper, a non-intrusive method, which estimates scroll and rotary compressor heat losses towards the ambient air, is presented. The number and location of temperature sensors required by the method in order to estimate the external thermal profile of compressor shell, is specified. The developed method can be integrated in the on-field performance measurement method. Coefficient of performance values for scroll and rotary compressors are estimated in two operating conditions and compared with reference COP values obtained from intrusive measurements. The outcome of this study is the number and location of surface temperature sensors in scroll and rotary compressors along with appropriate correlations for heat transfer coefficients in order to accurately estimate COP values of air-to-air HPs using the on-field performance measurement method.