Integral and Differential Model of Hermetical Compressor Heat Losses Including Experimental Validation

The current evaluation of heating and cooling system performances has become a major issue in European buildings sector. A promising method for measuring heat pump performances on-field has been previously developed and published. However, the accuracy of the method is strongly dependent on the evaluation of heat transfer from compressor towards the ambient air. In this paper a developed compressor heat transfer model that couples integral and differential formulations is presented. The model consists of three fundamental steps: thermodynamic analysis of the compression process, detailed thermophysical flow analysis using a CFD software, and finally compressor thermal network analysis consisting of integral equations that describe heat transfer of solid-fluid interfaces. Temperature distribution of the compressor shell is the main output of the model. Internal and external thermal profiles obtained from the numerical model and experimental measurements are compared in one operating condition at two compressor speeds. The RMS errors of external profiles are 3.20 °C and 1.96 °C, at 30 rps and 60 rps, respectively. The model can be used to determine the minimum number of surface temperature sensors and their locations on the compressor shell necessary to measure heat losses on-field. More accurate evaluation of compressor heat losses towards the ambient air will improve the accuracy of the performance measurement method.