Performance Study Of Heat Pump Air Conditioners For Electric Vehicles With Linear Compressors

The new energy vehicle industry is an important part of China’s strategic emerging industry,and an important part of achieving the goal of "carbon neutrality".The anxiety of driving range has always plagued the promotion of electric vehicles.As one of the important assemblies of electric vehicles,the energy consumption of air conditioning system accounts for 33%of the energy consumption of the whole electric vehicle,and the compressor is the most important energy-consuming component of the air conditioning system.Therefore,the development of high-performance compressors for heat pump air conditioning system of electric vehicles has a significant effect on the improvement of the range of electric vehicles.The linear compressor eliminates the crank linkage mechanism,has a compact structure,high efficiency,and can achieve oil-free operation and avoid start-stop operation,which has great potential for application in the heat pump air conditioning system of electric vehicles.In order to comprehensively explore the feasibility of replacing scroll compressor with linear compressor in the heat pump air conditioning system of electric vehicle,firstly,a test bench of heat pump air conditioning system based on linear compressor was built,meanwhile,a data acquisition and control system based on LabVIEW was constructed to control,monitor and collect system operation parameters such as piston amplitude frequency,evaporating pressure and temperature,condensing pressure and temperature,and mass flow rate.Using R134a as the working material,the cooling and heating performance of the linear compressordriven heat pump air conditioning system was experimentally studied at a pressure ratio of 2.0-3.0,compressor stroke of 40-50 mm and a condensing temperature of 40℃.The study results showed that the maximum system cooling COP was 4.31 and the maximum system heating efficiency was 4.01 at a pressure ratio of 2.0 and compressor stroke of 40 mm.Subsequently,the numerical model of linear compressor is established by combining the energy balance equation,compressor dynamic equation and heat transfer equation.The simulation results were validated based on compressor stroke,mass flow rate,and power input.The validation results showed that the overall error of the linear compressor numerical model is within±15%,demonstrating the reliability of the model.Based on this numerical model,the valve opening,piston displacement,cylinder temperature,discharge temperature,and thermodynamic efficiency of the linear compressor during operation are analyzed to study the performance of the linear compressor under different operating conditions.The numerical model of the scroll compressor heat pump air conditioning system is established,and the simulation verification of the established numerical model is carried out based on the existing literature test results.The verification results show that the overall error between the simulation system performance parameters such as condenser outlet temperature,evaporator outlet temperature,mass flow rate,power input,cooling capacity and COP and the test is within 15%,which verifies the simulation model of the scroll compressor heat pump air conditioning system.accuracy.The numerical model of the modular automotive heat pump air conditioning system was constructed by combining the numerical model of scroll compressor,linear compressor and microchannel heat exchanger model,and the cooling and heating performance of the two compressor-driven heat pump air conditioning systems were compared and analyzed under the same operating conditions.The simulation results show that the system COP of the linear compressor heat pump air conditioning system is about 26%higher than that of the scroll compressor heat pump air conditioning system under cooling conditions,while it is about 16.5%lower under heating conditions.Finally,based on the numerical model of a linear compressor,an numerical model of a two-stage compression air conditioning refrigeration system with a linear compressor is constructed,and the effects of two-stage pressure ratio,condenser temperature,and evaporator temperature on the performance of the two-stage compression air conditioning refrigeration system are analyzed.The results show that the maximum leakage of the two-stage compression refrigeration system is reduced by 40%compared to the single stage compression,and the refrigeration capacity and COP generated by the two-stage compression system are also 105.5%and 36.8%higher than the single stage compression system,respectively.The research results of the paper have certain guiding significance for the application of linear compressors in the field of two-stage compression heat pump air conditioning systems.