Electric Vehicle Two-stage Compression Heat Pump Air Condition System And Simulation Research

With the increasing market share of new energy vehicles,saving energy and increasing endurance become a research hotspot.The air conditioning system needs to consume plenty of electric energy in the automobile system,especially in the cold outdoor environment,the traditional single-stage compression heat pump is inefficient,so it is urgent to find a new energy-saving heating method.Based on the analysis of the two-stage compression thermodynamic cycle,the corresponding thermodynamic calculation program is compiled on MATLAB and EES platform to obtain the flow relationship between the two stages,and the relationship between the volume efficiency and the compressor pressure ratio is obtained according to the nominal working condition of the compressor.After inputting the corresponding evaporation temperature,condensation temperature and other parameters,the operating state parameters of the system can be output,and the optimal intermediate pressure of the heat pump cycle with R410 A as the refrigerant and the influence of various factors on the efficiency can be obtained,and the efficiency of single-stage compression and two-stage compression can be compared.In the modeling and Simulation of each component,it is based on Simulink platform.In the modeling of compressor,the flow rate and two-stage relationship of compressor are obtained through the exhaust capacity and speed.The modeling of parallel flow condenser involves many parameters.Through the empirical formula in the references,the heat transfer coefficient and pressure drop of air side and refrigerant side are obtained.The micro elements are divided according to the enthalpy difference,and the micro element tube length is calculated.Define the heat transfer coefficient function and verify the enthalpy function,and establish the algorithm flow of design calculation and check calculation.The modeling of evaporator is also based on parallel flow heat exchanger,which is simpler than condenser.The intercooler is modeled as a tubular heat exchanger,with two-phase and single-phase flow in the inner and outer tubes respectively,and the tube length of the output heat exchanger.Because the parameters of the system are coupled with each other,many iterative processes are involved in the process of building the model.On the basis of the model,the influence of heat exchanger structure parameters on heating capacity and subcooling,and the influence of air speed and temperature on the system are analyzed.Under the condition of determining the tube length,the influence of variable frequency operation realized by changing the speed on the heating capacity and COP of the system is obtained;and under different ambient temperatures,the relationship between the ambient temperature and the two-stage speed is obtained by controlling the superheat degree At the end of the paper,the thermal calculation program and the self defined function used in the construction of Simulink system are included in the appendix.