| Summary: | 碩士 === 國立臺北科技大學 === 能源與冷凍空調工程系碩士班 === 98 === As the restrictions on refrigerant by Montreal Protocol and Kyoto Protocol in ODP (Ozone Depletion Potential) and GWP (Global Warming Potential), to find a suitable refrigerant used in systems are worthy of study. While single stage air source heat pump water heater runs in conditions of low ambient temperature (-5℃~-25℃), it will face some problems. Such as: Compression ratio of the compressor will be oversized, the evaporator inlet quality will increase, and the discharge temperature of compressor will increase. These will make the overall system performance degradation. Therefore, if heat pump runs in conditions of low ambient temperature, it can overcome the above problem, and make the high efficiency, it should be investigated. The objective of this study is, through theory simulation parametric analysis for quasi-two stage air source heat pump system with economizer in the same compressor by R134a and HFOs refrigerants, to investigate performance under different operating conditions. To investigate the feasibility for HFOs as an alternative refrigerant to R134a. And HFO refrigerants which are R1234yf and R1234ze(E). The operating conditions of the condensing temperature is 40℃~50℃, and the evaporation temperature is -10℃~-25℃.The results show that: Comprehensive appraisal of R1234yf and R1234ze(E), the result shows that R1234yf is suitable than B to replace R134a for medium refrigerant of quasi-two stage heat pump system The refrigerant using R1234yf can increase the coefficient of performance about average 4.01% than R134a, and the discharge temperature of compressor reduced average 14.4℃. The obtained result of this study equivalent to Spatz and Minor [18].
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