Wind Evaporator Heat Pumps—Part I: Test Methods

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. It is believed that, in certain climates, wind evaporators can operate satisfactorily with frost on their surfaces for extended periods of time and defrost passively during switch-off periods. If so, an active defrost cycle would be unnecessary in these climates. Wind evaporators present an opportunity for heat pumps to be less expensive, more reliable, and more energy-efficient. However, the heat transfer performance of wind evaporators varies as a result of changes in a wide range of climatic variables. To determine the technical feasibility of wind evaporators, it is necessary to test complete wind evaporator heat pumps and to compare their monitored field performance over extended periods to that of conventional heat pumps with fan-assisted, finned-tube evaporators. In this paper, a test facility which allows side-by-side testing of wind evaporator and conventional heat pumps and monitoring of weather conditions is described. The choice of measurement technique for each variable is discussed and estimates of the measurement uncertainty for each sensor are made.