Wind Evaporator Heat Pumps—Part II: Thermal Performance Results

Wind evaporators are alternative evaporators for air source heat pumps which rely on wind-driven or natural convection to move air across the heat transfer surfaces. A fully automatic, computer-controlled test facility which allows side-by-side testing of wind evaporator and conventional heat pumps and monitoring of weather conditions has been designed and built at University College Galway. The aim of this paper is to quantify the advantages of wind evaporators by comparing the performance of a wind evaporator heat pump with that of a conventional heat pump over an extended testing period and by examining the relationship between weather conditions and heat pump performance. In this paper, results are presented in the form of plots of coefficient of performance (COP), compressor power, evaporator and condenser heat transfers and climatic variables against time. In addition, a testing period coefficient of performance has been calculated for each heat pump. The results show that wind speed is the dominant climatic variable affecting wind evaporator heat pump performance, and that frost growth does not significantly reduce this performance. Even at extremely low wind speeds, the COP of the wind evaporator heat pump is not significantly affected. After over 460 hr of testing, the testing period COP of the wind evaporator heat pump shows a 16 percent increase over that of the conventional heat pump. (Refer to Nomenclature in Part I of this paper.)