The Refrigeration System Simulation And Optimization Of Alternative Refrigerants Train Air-conditioning

Under the double request of protecting ozone layer and greenhouse gas emission reduction,more attention has been paid to the environmental protection performance of refrigerants.Currently,the research foundation of the domestic HCFC in the train air-conditioning industry is weak,and the refrigerant suitable for the train air conditioner is not clear.It is imperative to carry out the application research of alternative refrigerant in train air conditioning system.At present,the refrigerants mainly adopted in the train air conditioning are R22,R134a,and a small amount of R410A.The design of air conditioning system is involved in the research of refrigerant substitution,while the traditional train air conditioning design method needs to make a large number of prototype tests and adjust the structural parameters of the system,which is not conducive to saving energy and saving materials.Besides,the long design cycle delays the replacement research of refrigerants.The computer simulation technology of the refrigeration system can accurately predict the performance of the air conditioning products,and it can simulate the performance of air conditioning system under various cooling and heating conditions within a certain error range,which represents the development trend of air conditioning system design.In this paper,firstly the principle of screening the refrigerant for train air conditioning is put forward,R32 and R407C are selected as the refrigerants of train air conditioning,and the properties of refrigerants to be screened are analyzed theoretically.Then the experimental prototype and platform are designed to test the performance of train air conditioning system using alternative refrigerant.Afterwards,the steady-state simulation model of the train air conditioning system is set up,and simulation software for train air conditioning using alternative refrigerants is written,which is corrected and verified by the experimental data.Finally,the influence of the optimization scheme on the system performance is simulated based on the corrected model.The detailed research content of the paper is as follows:(1)The propertiesof R32,R134a,R407C,R410A and R22 systems are analyzed theoretically under the four refrigeration conditions design.The aspects of environment,safety,thermodynamic properties and economics are taken into account to screen alternative refrigerants suitable for train air conditioning.The refrigerant R407C and R32 are selected as alternative refrigerants for train air conditioners,and the performance of train air conditioners using R407C and R32 are tested.(2)Based on the working principle of refrigeration system and the latest research results at home and abroad,simulation models of compressor,heat exchanger,capillary tube,connecting pipe and heat exchange material are established,which are coupled to the refrigeration system.The simulation calculation of the refrigeration system is carried out by using the specified superheat and subcool algorithm,and then the simulation model is corrected.(3)A circuit arrangement optimization method based on genetic algorithm is proposed,which is used to optimize the circuit arrangement of evaporator.After several generations of evolution,it converges to an optimal way of circuit arrangement.A dimensionless entropy generation number is used to analyze and evaluate the comprehensive efficiency of the evaporator.It can be concluded from the optimization results that the dimensionless entropy generation number of the evaporator is reduced by 4%compared with that before optimization.Finally,the influence of optimizing circuit arrangerment on the system performance is calculated based on the system simulation model.(4)Based on the corrected simulation model,the layout schemes of heat exchangers and uniform wind structures are optimized.In addition,various heat exchanger layout schemes are compared and analyzed,which could obtain a better combination layout scheme of heat exchangers.At the same time,a kind of system co-simulation method is put forward,in which the CFD simulation of the heat exchanger air side is combined with the steady-state simulation model of the air conditioning system.It is shown that when the condenser tilt angle is 53 degrees and the evaporator tilt angle is 50 degrees,the cooling capacity of the system increases 4.44%,and the system EER increases 9.35%.Based on optimization scheme of the heat exchanger,the uniform wind structures are designed to reduce wind velocity mal-distribution of condenser.It is shown that under the rated cooling condition,the system cooling capacity increases from 38.08kW to 41.36kW,and the system EER increases from 4.19 to 4.54.