| Compared with the traditional fuel automobile, the electric car has the vantages of low noise and zero direct carbon emissions. With the increasing deepening energy crisis in the process of society development and energy saving and environmental pressure, electric automobile has become the auto industry development in the new direction of development. Compared with the fuel vehicle, electric vehicle has no engine waste heat for heating use. Among the many different heating schemes, the comprehensive performance of heat pump air conditioning system is better. This article mainly aims at the Haima-Aishang pure electric vehicle design a set of operation at low temperature under the variable conditions of heat pump air conditioning system. Based on the principle of quasi two-stage compression and combining with the relevant control method, the system solve the problem of low temperature performance of air source heat pump air-conditioning system environment of auto decay too quickly and defrost at the low efficiency. In this study, the compressor uses medium and low pressure ways to complement gas of the system. We build the heat pump air conditioning system test bench for electric car. The variable refrigeration mode, the dynamic characteristics of heating and the dynamic characteristics of the outside heat exchanger defrosting experiment has tested in the constant temperature and humidity test chamber. The dynamic characteristics of System heating condition experiments including exterior ambient temperature change influence on system performance experiment, variable speed of the compressor, variable air volume of condenser experiment, variable gas supplying mode experiment and electronic expansion valve opening variable experiment. The outside heat exchanger defrosting experiment including variable condensing air defrosting experiment, variable gas supplying mode and air compensating valve opening variable defrosting experiment.In this study, the system cannot stabilize and the exhaust pressure exceeds the limit pressure value 22 bar of the compressor working without the complement gas of the system, when the temperature of the environment system in vehicle to minus 15 degrees Celsius low-temperature heating. The system can run stably and reliably, system heating capacity reached 2881 W, the COP value is 1.45 with the loop of complement gas. When the environment temperature system in vehicle to minus 7 degrees Celsius at run time, heat production compressor maximum speed reached 3667 W, system COP value is 1.55. Performance meet the design requirements of the system, the ratio of PTC low temperature heating scheme is obvious more energy efficient. We set the superheat set value of the main valve under the optimal cooling conditions and we adjust the complement gas supply valve opening of the defrosting experiment. after the system operation for a period of time in the environment of low temperature and high humidity in the condition of defrosting. Under the surface wind speed is 1.6m/s of the outside heat exchanger, defrosting time is shortest at 60 s. System defrosting efficiency is improved obviously. Heat pump air conditioning system in electric vehicles the Institute of the paper designed and developed fully reflects the validity and reliability of the heat pump system. It can not only meet the demand of the car comfort, but also reached the purpose of energy saving and environmental protection. Lay the foundation of data and control method of this study concluded that for the development of further optimization and vehicle system of heat pump air conditioning system of electric vehicle. |
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