| Heat recovery heat pump hot water system is safe,efficient,energy-saving new hot water system.Commercial heat recovery heat pump hot water product has gradually been favored by the public in the market,but also gets many researchers attention.The paper analyzed a large number of research results about the heat pump and heat transfer.Combined with the experiment,the heat recovery heat pump hot water system mathematical simulation model using R410A as working fluid was established.Heat pump running process and the impact of various factors were analyzed using the mathematical simulation model.In the paper,the calculation formula of entropy,enthalpy,density and dynamic viscosity of R410A is established by combining the state equation of PR cubic with the deviation function theory and free volume theory.The polynomial fitting method was used to establish the calculation model of specific heat capacity,thermal conductivity and surface tension of R410A.All calculated results are compared with REFPROP sample data,and the average relative error is less than 6.3%.In the paper,IAPWS-IF97 recommended water model was used to establish the calculation model of water thermophysical properties and migration parameters,the average relative error between obtained results and the sample data is less than 2.0%.In the paper,the compressor steady-state efficiency model was used to establish the rolling rotor compressor simulation calculation model.The steady-state distribution parameter model was used to establish the simulation model of the casing condenser.The steady-state concentration parameter model is used to establish the simulation model of plate evaporator.According to the principle of equal enthalpy,the calculation model of electronic expansion valve was established.Combined with all the above models,the simulation model of heat recovery heat pump hot water system is established.The simulation results obtained are compared with those of the verification experiment.The average relative errors between the simulation results and the experimental ones are less than 10%.The model meets the requirements of engineering simulation applications.The simulation model was used to simulate the operation process and coefficient of performance of the heat recovery heat pump hot water system.From the analysis of the calculation results,it can be seen that the circulating water in the water tank is continuously heated and the temperature of the water continuously increases during the operation of the system.The evaporation temperature,the evaporation pressure,the condensation temperature and the condensation pressure in the heat pump system both increase,and the system power consumption rise,the system’s heating capacity decreased,the system’s performance coefficient decreased,the system’s heating capacity decreased.On this basis,the evaporator and the condenser heat transfer process was simulated during the operation of heat recovery heat pump hot water system.The results show that during the operation of the heat recovery heat pump system,the coefficient of performance of the system increases when the heat transfer area occupied by the two phase transformation heats in the evaporator and the condenser increases;when the area occupied by the two-phase transformation heat decreases,the performance coefficient of the system decreases,the system’s performance coefficient decreases.Based on the above analysis,we can see that in the heat recovery heat pump hot water system,two-phase transformation heat transfer process has a great impact on the heat pump performance coefficient.It can be inferred that the heat generated by the two-phase transformation heat exchanger in the heat exchanger is the main heat source in the heat pump working fluid circulation system.Continuously,the influence of the change of circulating water flow on the heat pump performance is analyzed in the paper.In the simulation calculation model,the recirculation water outlet temperature and system performance coefficient of the system were calculated respectively under the conditions of circulating water flow of 1.5m3/h,1.75m3/h and 2.25m3/h.From the analysis of the calculation results,it can be seen that the temperature of the circulating water of the system decreases with the increase of the circulating water flow,and the coefficient of performance of the system increases with the increase of the circulating water flow of the system.Meanwhile,The paper analyze the impact of heat exchanger structure size changes on heat pump system performance.In the simulation calculation model,32-plate,38-plate,44-plate,50-plate plate evaporator and tube-type condensers of 5.8m,6.4m,7m and 7.6m tube length are given respectively.The simulation results show that the performance coefficient of the system increases with the increase of the size of the bushing condenser and decreases with the increase of the size of the evaporator when the other conditions are not changed. |
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