| 摘要: | 冷媒HFC-134a與HFC-245fa是目前市面上常見的冷媒，兩者都是屬於沒有含氯離子的第三代冷媒，不會破壞臭氧層。而兩者的差異在於工作壓力的不同，HFC-134a 屬於高壓冷媒，因此使用在低溫的場所，像是冰櫃、車用空調、除濕機或冰水機等製冷設備中。而 HFC-245fa 屬於較低壓的冷媒，因此用在較高溫的地方，最常用於有機朗肯循環系統，回收工業廢熱，提升能源使用效率。
本研究比較兩種冷媒在山型紋板式熱交換器中的流動沸騰性能，以兩種冷媒為工作流體，測試山型紋角度65°的板式熱交換器，固定溫度30°C、冷媒流量分別為G=10，20，30到40 (kg/m2s)總共分為四個流量進行流動沸騰實驗，並比較其熱傳係數以及壓降。
總體而言，HFC-134a相較於HFC-245fa有較好的熱傳性能，因此前者的使用範圍較廣，但由於他的工作壓力較高，若是要使用必須先確保系統是否能承受他的高工作壓力。;Refrigerants HFC-134a and HFC-245fa are common refrigerants on the market at present. Both belong to the third generation refrigerants without chloride ions, which will not destroy the ozone layer. The difference between the two is the difference in working pressure. HFC-134a is a high-pressure refrigerant, so it is used in low-temperature places, such as freezers, car air conditioners, dehumidifiers or ice water machines and other refrigeration equipment. HFC-245fa is a lower pressure refrigerant, so it is used in higher temperature places, and is most commonly used in organic Rankine cycle（ORC）systems to recover industrial waste heat and improve energy efficiency.
In this study, the flow boiling performance of two refrigerants in a chevron plate heat exchanger was compared. The two refrigerants were used as working fluids to test a plate heat exchanger with a mountain-shaped pattern angle of 65°. The experiment condition was temperature at 30°C, and the refrigerant flow rates were respectively For G=10, 20, 30 to 40 (kg/m2s), a total of four flow rates were divided into flow boiling experiments, and the heat transfer coefficients and pressure drops were compared.
In general, HFC-134a has better heat transfer performance than HFC-245fa, so the former can be used in a wider range, but due to its high working pressure, if it is to be used, it must be ensured that the system can withstand his high work pressure. |
