Study On Air Conditioning Characteristics Of Special Cooling And Heating Heat Pump For Large Pure Electric Bus

The rapid growth of the number of cars has aggravated the problems of traffic congestion,air pollution and energy shortage.Bus is one of the main means of transportation in China.The development of pure electric bus has become an important measure to solve the above problems.Encouraged by various policies of our country,local governments have put in large quantities of pure electric buses,and the number of them is still growing.Reducing the energy consumption of key equipment and increasing the endurance mileage of pure electric bus are the main research directions of pure electric bus.Air conditioning system is an important part of pure electric bus,its energy consumption is as high as 1/3 of the total energy consumption of pure electric bus.Therefore,it is of great significance to develop an efficient and energy-saving heat pump air conditioning system for pure electric buses,which can reduce the energy consumption of pure electric buses and increase the endurance mileage.Based on quasi-two-stage compression and enhanced air-supply technology,this paper develops a set of special cooling and heating heat pump air-conditioning system for large-scale pure electric bus.The scroll compressor with supplementary air function is used in the compressor of the system.The environmental friendly refrigerant R410a with large unit refrigeration capacity is used as refrigerant.The micro-channel parallel flow heat exchanger with high heat transfer efficiency is used inside and outside the vehicle.The electronic expansion valve with sensitive regulation and high precision is used in both main and auxiliary circuits.The experimental results show that the system can operate steadily and efficiently at ambient temperatures ranging from-25?to 50?,and can meet the needs of comfort of people in buses.Under the standard refrigeration and heating conditions,the refrigeration capacity of the system is19.21kW,the heating capacity is 21.49 kW,the refrigeration performance COP and COP_E are 3.87 and 2.17 respectively,and the heating performance COP and COP_E are 5.53 and 2.7 respectively.The exhaust temperature of the system is as high as 90.73?when the system is not supplied with air at 50?high temperature,and the exhaust temperature can be effectively reduced to 74.61?with the supplementary gas technology.At the same time,the refrigeration capacity can reach 17.77%,and the refrigeration performance COP and COP_E are 2.53 and 1.67 respectively.When the system is not air-filled at low temperature environment-25?,the heat produced is only 9.48 kW,which is53.41%less than the standard heating condition.The heat produced by air-supplementation technology can reach 11.27 kW,which can be increased by18.88%,and the heat produced by COP and COP_E are 3.45 and 1.52,respectively.This heat pump air-conditioning system can increase the overall performance of the system under standard refrigeration and heating conditions,and then effectively solve the problem of excessive exhaust temperature of compressor under extreme high temperature environment,so as to ensure the safe and stable operation of the system,at the same time,increase the refrigeration capacity and improve the refrigeration performance of the system.Finally,under the low temperature condition of-25?,it can effectively reduce the attenuation of heat production and improve the heating performance of the system.