Performance Evaluation And Design Of Heat Pump Air Conditioning For Electric Bus

The energy security of the international community, extreme climate of the world and guide national policy making pure electric bus has become the future direction of the bus. However, an environmental protection, energy-efficient heat pump air conditioning system becomes one of the key technologies to prolong the endurance mileage of electric Bus.It’s designed a new heat pump air conditioning system which can run normally under variable conditions including extreme high temperature and low temperature, based on a set of 12 m large electric bus. The paper studied mainly the cooling and heating performance of the common bus air conditioning system and the developed new one and analyzed the test results. It also developed corresponding compressor to match the system on the basis of the principle of two-stage compression which can realize complement gas of middle-pressure and low-pressure. Besides, the internal and external heat exchangers have been improved to increase efficiency. It experimented on the common system and the new system for comparative analysis adopted medium pressure and low pressure mixed gas independently under variable working conditions changing the inside and outside air volume. Moreover, the rapid defrosting technology for the new system has studied by experimental test.The results shows that the change of environmental temperature brings enormous influence on the performance of the heat pump air conditioning system when ambient temperature raises, the heating performance would be improved, however, the cooling performance shows the opposite trend.When utilized scroll compressor the complement gas of middle pressure, refrigerating capacity can be improved and exhaust temperature reduced by 8-14℃.When applied the complement gas of middle and low pressure independently, heating capacity and COP can be advanced. The variable air volume outside experiments show that the change of the outside air volume has little effect on the system performance parameters which means that the outside air volume can be appropriately reduced, in the case of guarantee refrigerating and heating capacity.Change the air volume inside show that the system under different working condition of the heating conductor in different air volume changes. Under- 10℃, using medium pressure fill gas can increase heating capacity and COP by 21.8% and 13.3% respectively; Adopted complement gas of low pressure, the heat capacity and COP rise by 37.7% and 29.2% under the same condition. The new type system can defrost outside heat exchanger of the frost fast within 4 minutes, shortening the defrosting time greatly. New system improved the system performance and lower refrigeration cycle evaporator operation resistance by about 25% via optimizing interior heat exchanger process and effective area for the traditional system. New type heat pump air conditioning system can operate stably between the ambient temperature- 20℃ to 50℃.