| 摘要: | 板式熱交換器由於其有良好的熱傳導係數，體積小，有效度高等優點，已被廣泛應用在工業界。HFC-134a是目前市面上常見的冷媒之一，因其為不含氯離子的第三代冷媒，所以其臭氧層破壞係數(ODP)為0，故不會破壞臭氧層，且其低毒性，在空氣中不可燃，被歸類在安全類別A1，具有良好之綜合性能，用來替代上一代冷媒 CFC-12。而HFC-134a屬於高壓冷媒，適合用於低溫條件下，被廣泛應用於像是冰櫃、車用空調、除濕機或冰水機等製冷設備中。但伴隨著現代人對環境的要求越來越嚴格，第四代冷媒HFO-1234yf被開發出來取代第三代冷媒HFC-134a。
本研究為了瞭解冷媒在板式熱交換器中的熱傳與壓降特性，使用HFC-134a及HFO-1234yf為工作流體，測試在山型紋角度65度之板式熱交換器內熱傳性能與壓降，固定飽和溫度在30℃，並比較在不同冷媒流量下分別為G=10、20、30 kg/m2s，其熱傳係數與壓降。
實驗結果發現，兩種冷媒之壓降並無明顯差異；HFC-134a相較HFO-1234yf之熱傳性能略高約5%至14%，兩種冷媒熱傳係數皆隨著乾度上升而增加，在低乾度時熱傳機制以成核沸騰主導，熱傳係數與熱傳量成正比。
;Plate heat exchangers are widely used in industrial applications due to their excellent thermal performance, compact size, and high effectiveness. HFC-134a is one of the commonly used refrigerants in the market today. As a third-generation refrigerant that does not contain chlorine ions, it has an ozone depletion potential (ODP) of 0, thus posing no threat to the ozone layer. It is low in toxicity, non-flammable in air, and classified as safety category A1. Demonstrating good overall performance as a replacement for the previous generation refrigerant, CFC-12. HFC-134a is a high-pressure refrigerant suitable for low-temperature conditions, widely applied in refrigeration equipment such as refrigerators, automotive air conditioning, dehumidifiers, and chillers. With increasing environmental demands, the fourth-generation refrigerant HFO-1234yf has been developed to replace HFC-134a.
This study aims to understand the heat transfer and pressure drop characteristics of these refrigerants in a plate heat exchanger. Using HFC-134a and HFO-1234yf as working fluids, experiments were conducted on a plate heat exchanger with chevron angle of 65 degrees, maintaining a saturation temperature of 30°C. The study compares heat transfer coefficients and pressure drops at different refrigerant mass flow rates of G = 10, 20, and 30 kg/m2s.
The experimental results show that there is no significant difference in pressure drop between the two refrigerants. The heat transfer performance of HFC-134a is slightly higher, approximately 5% to 14% more than HFO-1234yf. Both refrigerants exhibit increasing heat transfer coefficients with higher quality. At low quality, nucleate boiling dominates the heat transfer mechanism, with heat transfer coefficients proportional to heat flux. |
