| The world’s climate problem, environment problem and energy problem have become increasingly serious today; electric vehicle has become the future vehicle development direction because of its advantages of zero emission, low noise and high efficiency. Same as the traditional fuel vehicle, electric vehicle also needs air-conditioning system to keep comfort in the car. A high efficient and energy saving air-conditioning system is also essential for electric vehicle. Electric vehicle has entirely different system structure with the traditional fuel vehicle, it has no engine to supply power source to the air-conditioning compressor, so compressor of the electric vehicle air-conditioning system is driven by motor directly. Due to the limited space of electric vehicle passenger compartment, arrangement of air-conditioning evaporator is restricted seriously, which requires evaporator unit volume to have a larger heat transfer rate. To solve this problem, double arrangement of micro-channel parallel flow evaporator is adopted; the thesis mainly focuses on the following contents:Firstly, establish R134 a physical properties rapid calculation model and moist air physical properties rapid calculation model, solve the precision and speed of the computer call, put forward moist air physical properties iterative calculation logic, and determine the standard of evaporator dry condition and wet condition.Secondly, set up steady-state simulation model of electric vehicle air-condition system main components, including scroll compressor model, thermostatic expansion valve model and refrigerant pipe model adopting lumped parameter method; micro-channel parallel flow condenser model and micro-channel parallel flow evaporator model using distributed parameter method. Considering void fraction, establish refrigerant charge model.Thirdly, carry on experimental study of the micro-channel parallel flow evaporator, and verify the accuracy of the above theoretical model. Through the experiment, effects of inlet air temperature, face velocity and refrigerant mass flow on heat transfer and flow performance of micro-channel parallel flow evaporator are researched. Through the simulation, effects of air-side structure like fin height, fin pitch, louver pitch and louver angle, and refrigerant-side structure like flat tube inner hole numbers, proportion of height and width of the inner hole and flow paths arrangement on heat transfer and flow performance of micro-channel parallel flow evaporator are researched.Fourthly, based on the foregoing components model, connect the components together according to equilibrium conditions, electric vehicle air-conditioning system performance steady state simulation model is established. Within the scope of the normal working conditions, effects of condenser inlet air temperature, evaporator inlet air temperature, condenser face velocity, evaporator face velocity, compressor speed and refrigerant charge on system performance are researched, and put forward corresponding optimization suggestions.Fifthly, on the basis of above simulation model, establish electric vehicle air-conditioning system design and performance simulation software platform, which can complete design calculation and simulation calculation, and has save and output function. The software platform has very outstanding practical value for vehicle air-conditioning designer. |
