| Summary: | 碩士 === 國立勤益科技大學 === 冷凍空調系 === 104 === This paper discusses how to operate R-134a refrigerant heat pump system stably in low temperature environment, so as to perform the optimum refrigerating and heating effects, and handles the problems of the air source heat pump system in low temperature environment effectively. For example, the compression efficiency decreases as the compression ratio increases, the heating capacity decreases as the compressor suction specific volume increases, even the excess exhaust temperature resulted from the increased compression ratio, the compressor is burnt down beyond the allowable operating range.
The household air source heat pump is connected to a vapor injection circuit in parallel to improve the applicability of heat pump system at different ambient temperatures. This study builds an air source heat cycling heat pump water heater unit, collocated with a flash tank to make the vapor injection circuit, and uses an electronic expansion valve for vapor injection flow control. The system is tested in environmental laboratory to analyze the operating parameters, including coefficient of performance, compression ratio and power consumption, under vapor injection valve openings 0%, 33%, 66% and 100% at ambient temperature of 5~35℃.
The experiment shows that the system with a vapor injection circuit can enhance the performance by 10% at ambient temperature of 20℃. In the environment at 5℃, the compression ratio is reduced effectively, the system safety is enhanced, and the compressor life is prolonged.
This paper discusses the control logic of refrigerant vapor injection quantity of vapor injection circuit at different ambient temperatures, hoping to find out the optimal control mode in different operational environments.
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