Simulation And Experimental Study On Performance Of Integrated Air-source Heat Pump And Freezer System

With the development of economy,the number of convenience stores and small supermarkets are increasing rapidly,and it's power consumption has also attracted widespread attention.In convenience stores and small supermarkets,the air-source heat pump and freezer system often operate separately,which not only waste resources,but also causes a certain degree of thermal pollution in summer.Therefore,how to achieve energy saving and emission reduction is of important significance.Integrated air-source heat pump and freezer system is proposed in this paper,which is coupled by a plate heat exchanger.The plate heat exchanger is used to connect the freezer system with the air-source heat pump system.At the same time,the condenser of the freezer system and the outdoor heat exchange of the air-source heat pump are integrated into one heat exchanger,that can provide a large degree of sub-cooling for the freezer system and it can delay the frosting of the outdoor heat exchange of the air-source heat pump in winter and reduce the defrosting frequency.In this paper,the theoretical analysis of integrated air-source heat pumps and freezer system is carried out.Firstly,the thermodynamic model of integrated air-source heat pump and freezer system is established.The program of calculating the performance parameters of integrated air-source heat pump and freezer system is compiled by using MATLAB and the thermophysical property parameters of refrigerant are invoked by using Refprop software.Secondly,the integrated system is simulated under different evaporation temperature,condensation temperature and mass-flow ratio.Finally,the performance of integrated airsource heat pump and freezer system is experimented in the enthalpy different laboratory.The effects of the relative humidity,mass flow ratio and outdoor temperature on frosting on the integrated outdoor heat exchange and the whole coupling system are studied and analyzed.The following conclusions are obtained.(1)The theoretical analysis shows that the performance of freezer can be greatly improved with the increase of the mass-flow ratio,but it has no effect on the heating capacity and COP of air-source heat pump system.Under the condition of constant evaporation temperature of the air-source heat pump system,the mass flow ratio increases by 6%,and the COP of the freezer system increases by 7.9%.The experimental results show that the mass-flow ratio has a certain effect on the heating capacity and COP of the air-source heat pump system.This is because an evaporator is connected in parallel in the experiment.Under the condition of constant evaporation temperature of the air-source heat pump system,the mass-flow ratio increases by 6% and the COP of the freezer system increases by 6.08%.(2)The experimental results show that heating capacity and COP of the air-source heat pump system increase firstly and then decrease with the frosting time under different relative humidity,mass flow ratio and outdoor temperature,the change range of the refrigerating capacity,power consumption and COP of the freezer system is very small.(3)The experimental results show that under the low relative humidity condition(70%,75%),the frost layer on the integrated outdoor heat exchanger is maintained at 0.035 mm and 0.170 mm,respectively and almost invariable,under the high relative humidity(80%),the frosting period is 120 minutes.Relative humidity has little effect on the average heating capacity and COP of air-source heat pump system,but the higher the relative humidity,the smaller the average COP of freezer system.(4)The experimental results show that under the condition of the mass flow ratio lower than 18%,it has little effect on the frosting period of integrated outdoor heat exchange of the air-source heat pumps.Under the condition of the mass flow ratio higher than 18%,the frosting period of outdoor heat exchange is dramatically shorten,which is disadvantageous to average heating capacity and COP of the air-source heat pump system.For freezer system,average sub-cooling degree,refrigerating capacity and COP all increase with the increase of mass flow ratio.Compared with single operation,the average refrigerating capacity increase by 10.7%~34.5% and average COP as 15%~50.2% respectively in the range of 6%~24% of mass flow ratio.(5)The experimental results show that expect for under the condition of outdoor temperature is-1?,the lower the outdoor temperature is,the shorter the frosting period of the integrated outdoor heat exchange of the air-source heat pump is,and there is no frosting under the condition of outdoor temperature is 5?.The lower the outdoor temperature,the smaller the average heating capacity and COP of the air-source heat pump system.For freezer system,the lower the outdoor temperature,the larger the average refrigerating capacity and COP,except for under the condition of outdoor temperature is-1?.Compared with the single operation,the average refrigerating capacity and COP of the freezer system under the condition of outdoor temperature is-1?increased the most,31.9% and 30.9% respectively.(6)The experimental results show that the frosting period of integrated outdoor heat exchange of air-source heat pump is prolonged by 117% and 14.3% respectively under the condition of outdoor temperature at-1?and-5?.The average heating capacity and COP are improved to some extent.The average heating capacity increases by 3% and average COP as 4.86% under the condition of outdoor temperature is-1?,average heating capacity increases by 4.59% and average COP by 5.59% under the condition of outdoor temperature is-5?.