:::

臺灣能源期刊論文全文

臺灣能源期刊第3卷第1期內容

出刊日期:March, 2016

題目
R134a螺桿膨脹機ORC應用於低溫熱水發電及其 特性研究
Title
Characteristics of R134a-ORC Applied in Heat Recovery of Hot Water
作者
吳孟儒、王大維、徐菘蔚、黃金文
Authors
Meng-Ru Wu, Ta-Wei Wang, Sung-Wei Hsu, Jin-Wen Huang
摘要
工業廢熱佔其使用燃料熱能的40%~60%,中低溫工業廢熱(溫度<350oC))又佔工業廢熱排放 量~80%。本研究以80oC~83oC的熱水為熱源,冷卻水塔的冷卻水為冷源,設計開發一款20 kW級發 電量的R134a螺桿膨脹機有機朗肯循環(ORC)系統。藉由系統分析及系統性能測試結果,發現(一) 低溫熱源條件時,R134a之ORC系統比R245fa系統具有高發電量、高效率、及機組體積小等優點; (二)設計點的系統性能測試結果顯示,當工作流體進入螺桿膨脹機的過熱度愈低,ORC性能表現 越佳;(三)離點的系統性能測試結果顯示:(1)工作流體蒸發溫度調降時,R134a質量流率、冷凝溫 度、發電機效率、發電量、及系統熱效率隨之降低;(2)系統膨脹比高於螺桿機內建膨脹比時,螺桿 膨脹機等熵效率維持於63%以上。系統膨脹比略高於螺桿機內建膨脹比時,可獲得最佳的螺桿膨脹 機等熵效率;(3)系統膨脹比低於螺桿機內建膨脹比時,螺桿膨脹機等熵效率快速下降,ORC系統 正常運轉時,應避開此操作區間,以獲得高的發電量。由本研究成果知:R134a之螺桿膨脹機ORC 適用於低溫熱能發電,且系統穩定,發電成本低,具備經濟效益及節能減排功效。本研發成果可直 接應用於低溫工業廢熱、地熱/溫泉、生質熱能及太陽熱能發電,可促成國內低溫發電產業。
關鍵字
工業廢熱、有機朗肯循環、螺桿膨脹機、膨脹比
Abatract
Due to the huge amount of low temperature waste heat discharged from industry, a 20-kW R134a- ORC system was designed and constructed for heat recovery of 80oC~83oC hot water and 30oC coolant water. A twin screw expander was induced in this system. A series of tests were designed and performed to investigate its performance at design point and off-design point. System optimization shows that R134a ORC system with high pressure working fluid has larger power output, higher efficiency and more compact structure than the R245fa ORC system. At design point, the higher superheat degree of working fluid at expander inlet, the lower power output. The off-design performance shows that (1) lowering the evaporation temperature will cause the decrease of R134a flow rate, condensation temperature, alternator efficiency, power output and system efficiency; (2) The optimum expander isentropic efficiency can be achieved while the system expansion ratio is a little higher than the built-in expansion ratio of screw expander; (3) The isentropic efficiency of screw expander will decrease rapidly while the system expansion ratio is lower than the expander built-in expansion ratio. The developed R134a screw expander ORC has a wide operation range and performs stable power output. It can be used for heat energy conversion to electricity in waste heat, geothermal, biomass, and solar thermal energy.
Keywords
industrial waste heat, organic Rankine cycle, screw expander, expansion ratio