| In order to relieve environmental problems such as greenhouse effect and ozone layer destruction,refrigeration and air conditioning industry is constantly studying new environment-friendly refrigerant to replace the traditional refrigerant R22 with high GWP and non-zero ODP.At present,environment-friendly HFOs are regarded as the most promising refrigerants for next generation.R1234ze(E),which belongs to HFOs is environment friendly,but has the defect of insufficient cooling capacity per unit volume.The previous research showed that the mixture of R1234ze(E)and R152a with a mass ratio of 40:60 could be used as a substitute for R22.Therefore,as a long-term substitute of R22,it is of practical significance to further study the circulation performance of the mixed working medium used in room air conditioners.Firstly,based on the PR equation used to calculate the vapor-liquid state parameters,combined with the VDWs mixing law and the basic knowledge of the vapor-liquid equilibrium theory,the vapor-liquid equilibrium calculation model suitable for R152a/R1234ze(E)was constructed and verified by the experimental data of the vapor-liquid equilibrium of the mixture.The correlation functions of temperature,pressure,component ratio and specific volume in the gas phase and liquid phase of the mixture were obtained.The maximum and average errors of saturated gas and liquid phase pressure obtained by this model are 0.617%and 0.135%,respectively.Secondly,based on the relationship between temperature,pressure and specific volume,combined with the residual property function,the enthalpy and entropy calculation model was further established.Taking the enthalpy and entropy value of the saturated liquid at 273.15K as the reference point,the enthalpy and entropy value of R152a/R1234ze(E)in a certain temperature range was calculated.The corresponding theoretical data are provided for the application of R152a/R1234ze(E).Finally,the mathematical models of the compressor,condenser,throttle valve and evaporator are established by using the relevant knowledge of refrigeration principle and combining with some property parameters and structural parameters of the actual equipment,such as the isentropic efficiency of the compressor,theoretical gas transmission volume and gas transmission coefficient,as well as the physical laws followed in the operation process.The mathematical model was transformed into a physical model using Simulink platform,and the gas-liquid equilibrium calculation model and the enthalpy and entropy calculation model were embedded into the model to complete the construction of the room air conditioner circulation simulation system.The constructed simulation system is used to test the cycle performance of R152a/R1234ze(E)under the condition of air conditioning and variable condition.By comparing the cycle performance of R22,it is found that the cycle cooling capacity of R152a/R1234ze(E)and the cycle power consumption of the compressor are about 41%and 43%lower than that of R22 under the condition of air conditioning,respectively.Under the variable condition,the cycle cooling capacity of R152a/R1234ze(E)in summer is 43.97%～52.66%lower than that of R22,and the cycle power consumption is 29.73%～46.96%lower than that of R22.COP was 8.23%-17.26%lower than R22;In winter,the cycle heating,cycle power consumption and COP were 35.85%～65.28%,25.16%～55.50%and 17.46%～29.67%lower than that of R22.According to the simulation results,the biggest defect of R152a/R1234ze(E)used in room air conditioners instead of R22 is the insufficient cooling capacity or heat generation.It is suggested to increase the gas transmission capacity of the compressor,recycle the cold capacity by using the heat exchanger to increase the undercooling degree,and optimize the circulation system to improve the cooling capacity or heat generation,so as to meet the needs of room air conditioning. |
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