Construction And Thermodynamic Performance Research Of Dual-source Heat Pump System Based On Non-azeotropic Mixtures

In response to the instability of single source heat pumps and the inability of single working fluid to provide different evaporation and condensation temperatures simultaneously in dual source heat pump system,a double source heat pump system based on non-azeotropic mixtures is designed.The system is available different evaporating and condensing temperatures,while utilizing two heat or cold sources,which can effectively reduce irreversible losses.The main research contents and conclusions of this article are as follows:(1)A dual source heat pump system based on non-azeotropic mixtures was constructed,and three application conditions and corresponding working fluids were determined according to the different application situations;The thermodynamic performance of the dual source heat pump system under design conditions is calculated theoretically through a calculation model.(2)According to the heating condition,an experimental platform was built.By comparing the calculated value with the experimental value,the maximum absolute error of temperature at each state point was less than 7℃,and the maximum relative errors of compressor input power,condenser heating capacity and coefficient of performance(COP)were less than 7%,6% and 2%,respectively,which verified the accuracy of the calculation model.(3)In the three operating conditions,the compressor input power decreases with the increase of evaporation pressure and increases with the increase of condensation pressure,and the evaporation pressure has a significant impact on the compressor input power;The COP of the system increases with the increase of evaporation pressure and decreases with the increase of condensation pressure.For each 0.1MPa increase in evaporation pressure,the COP of the system increases by an average of 13% to 16%;The COP of the system decreases by an average of 3.5% to 6.1% for each 0.1MPa increase in condensation pressure.Therefore,when using two different heat source temperatures in a dual source heat pump system,it is necessary to consider the changes in the degree of influence of two operating parameters,evaporation pressure and condensation pressure,on the COP of the system.(4)With the increase of the mass components of the low boiling point working medium,the three working conditions have the same points: the input power of the compressor increases,the heat absorption capacity of the evaporator increases,and the heat generation capacity of the condenser increases.The main reason is that the specific enthalpy and pressure of low boiling point working fluids are higher than those of high boiling point working fluids at the same temperature.Therefore,the mass components of low boiling point working fluids increase,the suction and exhaust pressures increase,the compression ratio decreases,the compressor input power increases,the condenser heating capacity increases,and the evaporator heating capacity increases.Differences: Under heating conditions and temperature and humidity independent processing conditions,the system COP first slowly decreases and then gradually increases;Under dry conditions,the system COP increases.Due to the increase of the low boiling point refrigerant mass fraction from 0.2 to 0.4 in heating conditions and temperature and humidity independent processing conditions,the compressor input power growth rate is greater than the condenser heating capacity growth rate and evaporator heat absorption growth rate,while the increase from 0.4 to 0.6 is less than the condenser heating capacity growth rate and evaporator heat absorption growth rate,so the system COP first slowly decreases and then gradually increases.