汽車空調機換裝電子膨脹閥與碳氫冷媒之研究

Abstract

因應全球暖化與歐盟F-Gas規範等法規限制，傳統汽車主要使用的R-134a冷媒已經受到管制。因此尋求符合環保法規的替代冷媒成為當前迫切課題。本研究將傳統汽車R-134a空調系統（MACs）換裝電子膨脹閥（EEV）與碳氫冷媒（R-290與R-600a）以配合不同冷媒的飽和特性、環保法規以及提升MACs的運轉效能。MACs性能實驗是參考CNS 7897-D3079標準的環境條件與壓縮機轉速進行測試，此外增加30 ℃與40 ℃兩個外氣條件以瞭解外氣溫度對於MACs運轉性能的影響。研究結果顯示， R134a-MACs將感溫膨脹閥(TEV)換裝成EEV之後，在相同充填量(600g)的條件之下，EEV的最佳過熱度為20℃。最佳的性能係數(EER)發生在外氣溫度為40 ℃，呈現高環境溫度之下有較佳的EER。在外氣溫度為40 ℃的條件之下，壓縮機轉速在1000 rpm與1800 rpm使用EEV的EER分別比TEV高11%與7%。R134a-MACs使用EEV可以成功地換裝R-290與R-600a。R-290的最佳充填量為180 g(約R134a的30%）即可達到與R134a近似的出風溫度。換裝R290之後的最佳EER發生在外氣溫度為30 ℃，呈現低環境溫度之下有較佳的EER。在外氣溫度為30 ℃的條件之下，R290在壓縮機轉速1000 rpm與1800 rpm的EER分別比R134a高14%與27%。MACs使用EEV換裝R-600a最佳填充量為270 g (約R134a的45%），R-600a在三種外氣溫度條件下，出風溫度上升1 ℃左右，EER則提升了10%-20%。以R-134a為比較基準，使用R-290冷媒評估總當暖化影響（TEWI），運行1-8小時減少3%的排放量。使用R-600a冷媒評估TEWI，運行1-8小時減少44%的排放量。相關研究結果顯示R-600a比R-290更適合作為R-134a的替代冷媒，且能有效地達到節能與環保目的。

In response to global warming and regulatory restrictions such as the EU F-Gas Regulation, the use of R-134a—traditionally adopted in mobile air conditioning systems (MACs)—is increasingly regulated. As a result, identifying environmentally compliant alternative refrigerants has become an urgent issue. This study investigates the retrofit of conventional R-134a MACs with an electronic expansion valve (EEV) and hydrocarbon refrigerants (R-290 and R600a), to enhance system performance while meeting environmental and thermodynamic criteria.Performance testing was conducted under environmental conditions and compressor speeds specified by CNS 7897-D3079, with additional tests at outdoor ambient temperatures of 30 °C and 40 °C to examine the impact of outdoor ambient temperatures on system efficiency. Results show that replacing the thermal expansion valve (TEV) with an EEV under the same R-134a charge (600 g) yields an optimal superheat of 20 °C. The highest energy efficiency ratio (EER) occurred at an outdoor ambient temperatures of 40 °C, indicating improved performance under high-temperature conditions. At compressor speeds of 1000 rpm and 1800 rpm, EEV-equipped systems achieved EER improvements of 11% and 7% at outdoor ambient temperatures of 40 °C, respectively, compared to TEV systems.Further experiments confirmed the feasibility of substituting R-134a with R-290 and R-600a using EEVs. An optimal R-290 charge of 180 g (about 30% of R-134a's charging mass) produced comparable supply air temperatures. The highest EER for R-290 occurred at an outdoor ambient temperatures of 30 °C, with gains of 14% and 27% in EER at 1000 rpm and 1800 rpm, respectively, compared to R-134a. Similarly, retrofitting with R-600a showed that an optimal charge of 270 g (about 45% of R-134a's charging mass) resulted about 1 °C increase in supply temperature across all test conditions, and enhancing EER by 10%–20%. Using R-134a as a comparison benchmark, using R-290 refrigerant to evaluate the total equivalent warming impact (TEWI), running for 1-8 hours reduces emissions by 3%. Using R-600a refrigerant to evaluate TEWI, running for 1-8 hours reduces emissions by 44%. Related research results show that R-600a is more suitable as a replacement refrigerant for R-134a than R-290, and can effectively achieve energy conservation and environmental protection goals.