Research On Dynamic Performance Of Air Source Heat Pump Under Frosting Conditions In High Humidity Area

Air source heat pump is widely used as a building cold and heat source in China.However,frosting is the primary factor that affects the operation effect of the unit.Therefore,the research on frosting and defrosting of air source heat pump has been carried out extensively.The temperature and humidity of the outdoor are quite different in north and south China.In the south of the Yangtze River,the unit is prone to work without defrosting;in the north,it is usually to be defrosting without forsting.These seriously affect the heating capacity of the unit.In this paper,theoretical model and experimental analysis were carried out for the frosting problem of air source heat pump caused by the typical environment characteristics of low temperature and high humidity in Guiyang.This paper analyzed the trend of dynamic performance of the unit under different conditions,and summarized the frosting rule of air source heat pump in Guiyang.According to the rules of frost formation,a method of frost suppression by stages was proposed.Firstly,this paper have reviewed the development of air source heat pump defrost experiments and theoretical research.Based on previous results,a dimensionless frost forecast model suitable for Guiyang was derived.The error was controlled in ±15%,which proved that the model has well reliability.Secondly,frosting experiments,blocking degree experiments and dew condensation experiments of the air source heat pump in Guiyang were carried out.The experimental results show that: the frosting conditions in Guiyang should meet environment temperature ?6? and RH?75% simultaneously;air source heat pump is recommended for heating at 6 ? to 18 ?;frost suppression measures shall be taken timely when it is below 6 ?.When the degree of frost blocking is 10%,the unit's performance is optimal in all aspects for the initial frosting is helpful to heat exchange.Because of the time inconsistency of frost covered finned tubes,staged frost suppression method was proposed.Finally,frost suppression experiment was carried out for the idea of defrosting by stages.The experimental results show that: the heat capacity by frost suppression is about 1.15 times that without frost suppression;frost suppression extends the time of initial frosting by 22 minutes.The total running time of the frost suppression by stages and non-frost suppression is basically the same,but the frost suppression prolongs the time of initial frosting.So,the heat exchange is enhanced,improving the thermal comfort.