히트펌프 시스템의 열원 및 팽창장치 변경에 따른 냉매 충전량에 관한 실험적 연구

Abstract

Upcoming technology for the environmental climate control system of fuel cell driven vehicle is heat pump system. The fuel cell driven vehicle has no engine to drive. Which means there is no heat source to heating up the compartment because the heating of the compartment is performed by the hot water from the engine. The hot water with antifreeze fluid supplies heat to the heat core that is located at inside of the compartment. The heat pump system uses heat from the outside air or heat from the coolant heat of the fuel cell. Heat pump system performance is strongly dependent on the efficiency of a compressor and composition of the components assembled to the system. Optimum charge of the working fluid(refrigerant) is the other factors of it. In this study, the experiment was performed to get the optimum refrigerant charge amount of the system. The system uses the waste heat from the fuel cell which is supplied to the heat pump system. The heat pump system can be operates three types of driving mode. Reference system uses the air heat passing through the evaporation as conventional heat pump system. Second configuration is the system uses waste heat from fuel cell stack through out the plate heat exchanger. The last configuration is the stack heat supplied to the air pre-heater which is located in upstream flow of air source heat exchanger. The air pre-heater is also work as defrosting device of the outdoor heat exchanger when the frost accumulated on it. The system was tested by varying refrigerant charge amount. The test was conducted at 7℃ DB and 6℃ WB in outdoor air temperature and 20℃ DB and 15℃ WB for the outdoor air conditions. And also the temperature of stack simulator is set at 40℃. All test was performed at 1,800rpm of compressor rotation speed. As results, optimal charge of the system with 1.5RT capacity EEV as expansion device is determined at 1,150g. When the EEV opening is 100%, is 4.37 in air source, 4.89 in air pre-heating source, and 5.18 in water source. When the system is equipped with a receiver to verify the saturation refrigerant to the evaporator, it showed that the is 4.07 in air source, 4.59 in air pre-heating source, and 5.89 in water source with same openings of the expansion device at 100% respectively. The optimum charge amount in system in this configuration is determined at 1,300∼1,400g refrigerant. When the expansion device capacity is increased from 1.5RT to 3.0RT, the optimum charge is fount out at 1,000g with 4.69 in air source, 4.79 in air pre-heating source, and 5.56 in water source. Mean while the system changes the expansion device EEV to TXV, the optimum charge is determined at 2,300g with 4.58 in air source, 4.63 in air pre-heating source, and 4.13 in water source.