Experiment on defrosting performance of air-source heat pump unit

To study the effect of performance of air-source heat pump units,which is caused by using different expansion device and different methods,compares two methods based on using thermal expansion and the electronic expansion as the expansion device of the air-source heat pump unit including defrosting by directly reversing four way valve and defrosting by reversing four way with compressor off.The result shows that the period of machine with electronic expansion is 12 seconds or 11% shorter than that with thermal expansion electronic valve,so suggests integrating both two methods by using the electronic expansion and by reversing four-way with compressor off.It keeps the capability of four way and,in a certain extent,it can solve the problem of pouring oil in from compressor,in the mean time,it can shorten period by using the expansion valve.