Deffrosting Process Analysis Of Fin Tube Of Air Source Heat Pump Outdoor Heat Exchanger

Air source heat pump has a very wide range of applications, it has many adventages: equipment for both winter and summer, convenient installation, convenient operation and management, energy saving and environmental protection, wide application scope etc. But when the air source heat pump runs in winter, if the temperature of heat pump outdoor coil outdoor is lower than the dew point temperature of outdoor air and the freezing point of water, the outdoor coil surface will be frosting. When frost accumulates to a certain extent, it is needed to defrost the outdoor heat exchanger.Air source heat pump reverse circulation process usually consists of three stages: the first stage, the fan stops rotating, so that as soon as the increase of condenser temperature; the second stage, frost melting and in avoid the heat loss to the surrounding air heat exchanger, the fan continues to stop; the third stage, the fan starts, mainly in order to have the melted water to be dried. For the defrosting process of single-tube of air source heat pump outdoor heat exchanger, two kinds of defrosting models are established, an experiment table is built. The single tube is transformed into the frosting and defrosting model respectively by controlling the switch of the three-way valve. In defrosting process, the temperature of circulating solution is changed to 40℃、30℃、20℃,10℃、5℃, at the same time, theoretical analysis is carried out for the defrosting process. The experiment results and theoretical analysis show that defrost efficiency has little change with the increase of temperature of the circulating solution under different temperature of the circulating solution; the higher the temperature of the circulating solution, the better the defrosting effect; the higher the temperature of the circulating solution, the heating time of thermostatic bath is longer and the heating efficiency is lower.The melting process is divided into two kinds of situations, and the two models are established according to the two conditions: By comparing the theoretical model A and the experimental data, the conclusion is obtained: The results of the model are in good agreement with the actual value of the solution while the temperature of the circulating solution is high, but there are some differences between the model calculation results and the experimental values while the temperature of the circulating solution is low; The time of first defrosting stage, the time of second defrosting stage and the total time are all decreased with the increase of the temperature of the circulating solution. The percentage of the first stage of the total melting time is little, and the maximum is no more than 10%; Different fin materials have great influence on the time of first defrosting stage, but have little effect on the total defrosting time; With the increase of hi value of the heat transfer coefficient, the total defrosting time is decreased, and the total defrosting time changes more rapidly when the hi value is small; The smaller the ti value of the circulating solution, the higher the effect of the hi value of the heat transfer coefficient on the total defrosting time; With the decrease of hiti value, the change of the total defrosting time is more quickly.