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臺灣能源期刊論文全文

臺灣能源期刊第4卷第1期內容

出刊日期:March, 2017

題目
單歧管太陽能集熱板效率實驗研究
Title
Experimental Study on Performance of Single-Fin Solar Collector
作者
曾國哲、張克勤
Authors
Kuo-Che Tseng, Keh-Chin Chang
摘要
本文探討兩種不同型式之單歧管單鰭片平板型集熱板,其差異在於歧管分別置於向陽面與背陽面,並搭配五種入口流體流量進行太陽輻射光日照實驗。研究發現歧管置於向陽面的集熱板模組(FPC-1),歧管因直接被日照光照射,故集熱板內部能量傳導的路徑相對較短,當入口流量小時,在低熱散條件下的效率最高,約0.66;但隨著流量增加,逐漸下降至0.62以下。相對之下,歧管置於背陽面的集熱板模組(FPC-2),內部能量由吸收板被陽光照射後,經由集熱板內部的熱傳導及水管管璧熱對流來傳遞能量。當入口流量小時,其集熱系統的效率較低,約0.60;隨著流量增加至約一倍標準流量,其最佳效率達至高峰值,約0.63;爾後又隨流量增加而略為下降。兩種模組間的集熱效益差異來自受熱條件以及結構上的差異。FPC-2在大部分的天候、流量條件下,其吸收太陽能的效能較佳;而FPC-1其優勢僅在於入口流量低(約0.180 ℓ/min)且系統均溫(Tm)與環境溫度(Ta)溫差小或是日射量(G)大時(亦即(Tm-Ta)/G小於0.041oC • m2/W) 的情況下才會發生。由本研究結果得知,在兩種所測試集熱板模組中,FPC-2是使用條件(日照、環境溫度、流量)範圍較廣泛、聚熱效率相對理想的集熱板模組。
關鍵字
平板型集熱板、太陽熱能、準動態效能測試
Abatract
This study investigates the performances of the flat-plate solar collectors constituted of single tube and single fin. There are two different types of flat-plate collector (FPC) in this study. The first one is that the FPC tube is mounted on the sunny side; while the second one is that the FPC tube is mounted on the back of the sunny side. ISO 9806:2013 records a quasi-dynamic test (QDT) on FPC performance under variable and real weather conditions. Based on the standard of QDT, two types of FPCs were tested with five different inlet flow rates in Tainan, Taiwan for their performance analyses. The tube of the first FPC module was irradiated by the solar radiation directly, so the energy transferring path was comparatively shorter. At a small inlet flow rate, the optimal efficiency without heat loss (η0) of the FPC was almost 0.66. η0 decreased gradually as the inlet flow rate was increasing. In the second FPC module, solar radiation irradiates to the absorber plate of the FPC. The heat was transferred to the tube of the FPC via thermal conduction. At a small inlet flow rate, η0 of the second FPC was at most 0.60. As the flow rate was increasing, η0 is increased gradually to 0.63 at around the standard inlet flow rate stated in ISO 9806:2013: then, η0 is decreased as the flow rate increases further. In the first FPC module, the tube of the FPC contacted the air layer inside the FPC system directly, so the mean temperature of the FPC was higher in the process of solar energy absorption. As a result, the degree of heat loss of the first FPC is higher than the second FPC. In the present study, the temperature of work fluid is increased about 5~10oC as passing through the FPC system. Because the average temperature of FPC system is higher than the ambient one, the heat loss of FPC system occurs certainly. It led to that performance of the first FPC module is worse than the second one. The only advantage for the first FRC module is observed under the conditions of the small inlet flow rate (0.180 l/min) together with the small temperature differences between the system and the environment or the high global solar radiation (i.e., (Tm-Ta) / G < 0.041oC • m2/W).
Keywords
Flat-plate collector, solar energy, quasi-dynamic test