- 學位論文
毛細泵吸環路和雙相熱虹吸環路在太陽能熱水器的應用
Feasibility Study of the Capillary Pumped Loop (CPL) and Two-Phase Closed Loop Thermosyphon (TPCLT) Applied in a Solar Water Heater
摘要
本文主要目的是提出毛細泵吸環路(CPL)和雙相熱虹吸環路(TPCLT)在太陽能熱水器上的應用。以實驗測試的方式針對各環路在不同操作條件下的性能進行探討。 首先本文提出一個新型的CPL太陽能熱水器並且研究其特性。此新型太陽能熱水器的特色是擁有一個欄杆型的集熱器，並且使用CPL作為熱傳工具。實驗方式是量測此CPL在不同加熱功率、填充量、以及傾斜角度下的蒸發部的溫度分佈與轉換效率。根據實驗結果，最佳填充率為70%，而轉換效率最高可以達到77%。另一方面，實驗結果也顯示CPL太陽能熱水器只能在一定的加熱功率區間穩定運作。當傾斜角度為0∘時，CPL太陽能熱水器可以在加熱功率150W到300W之間穩定運作；當傾斜角度增加，可以穩定運作的加熱區間也跟著增加。 由於工作流體的填充率對於雙相熱虹吸環路太陽能熱水器的效能與啟動時間有著關鍵性的影響，因此利用在蒸發管內加入毛細結構來提高雙相熱虹吸環路太陽能熱水器在高填充率下的性能。根據實驗結果可以得知，當蒸發管內加入毛細結構可以減少環路的啟動時間跟增加環路的轉換效率，尤其是在低加熱功率。當加熱功率為360W時，系統的最高效率為68%。 前面的實驗所設計的太陽能熱水器都是小尺寸而且都是在實驗室的環境進行實驗，所以設計了一組大型的雙相熱虹吸環路太陽能熱水器，並且分別在實驗室跟戶外的環境測試。實驗室環境的結果顯示此系統填充量為70%且在加熱功率為630W時，熱轉換效率為69%；填充量為60%且在加熱功率為630W時，熱轉換效率為63%。而在系統填充量為70%時，最低可啟動的加熱功率為270W，填充量為60%時，最低可啟動的加熱功率則為180W。而在戶外環境使用的結果顯示此系統的儲水槽內的水溫達到42度。
並列摘要
The objected of this paper is propose using capillary pumped loop (CPL) and two-phase closed loop thermosyphon (TPCLT) applied to a solar water heater. Experimental investigation of performance of CPL and TPCLT in different condition. Due to those devices are high-efficiency heat transfer device capable of transporting thermal energy over long distances without the need for other mechanical forces, such as pumps. This makes CPL and TPCLT particularly suitable for applications involving solar water heaters and apply on the building integrated solar water heater. First, we presents an experimental examination of a railing-type collector solar water heater, employing a CPL as a heat transfer device. The structure and characteristics of the CPL solar water heater are also outlined. We conducted various experiments to investigate the start-up behavior and thermal storage efficiency under various filling ratios with different heat loads and tilt angles. Experiment results revealed that 70% is the ideal filling ratio for a CPL and that the heat load presents critical limitations with regard to stable operations. The highest thermal storage efficiency obtained in this study was 77%. We also determined that when a railing-type collector has a non-zero tilt angle, loose limitations pertaining to heat load can be relaxed without sacrificing stable operations. The first experiment results show that the fill ratio of the working fluid has a critical impact on the performance and start-up time of TPCLTs. Our objective in this work was to increase the performance of TPCLT solar water heaters by using an evaporator with a porous wick structure (PWS), especially in low heating power. Our results demonstrate that employing a PWS within the evaporator can enhance efficiency by 12.7% and decrease start-up time by 26.5% under low heating power. The above experiment setup all use small scaler solar water heater and operating in laboratory environment. Therefore, we designed the larger scaler TPCLT solar water heater and operating in laboratory environment and outdoor environments. In laboratory environment, the results shows that the efficiency is 69% in filling ratio 70% with heating power 630W. The efficiency is 63% in filling ratio 60% with heating power 630W. When the system is in filling ratio 70%, the lowest start-up heating power is 270W. When the system is in filling ratio 60%, the lowest start-up heating power is 180W. In outdoor environment, the water temperature can reach 42 OC.