- 學位論文
迴路式熱管儲能系統之研究
Investigation of Loop Heat Pipe Energy Storage System
摘要
近年來，由於能源使用量漸增與環保意識高張，如何有效利用或回收能源，便成為各方研究之重點。而儲能系統是其中相當重要的一環，在運用自然資源或將廢熱回收之情形下，減輕興建電廠的負擔；同時保護環境而不造成汙染。而利用工作流體相變化以傳遞熱能的迴路式熱管，不僅具備熱傳效果佳、成本低廉之優點，同時其被動式設計使其相當可靠，因此具有成為儲能系統的潛力。本研究即以兩相迴路式熱管為熱傳系統，設計一套由蒸發端吸熱、冷凝端釋熱，並將能量儲存於水中之儲能系統。本實驗採用三類不同之蒸發管，包含平滑管、燒結管及網格管，並以不同的加熱功率、系統充填率及工作流體做為實驗參數，進行每次兩小時之實驗。本實驗目的在於以毛細結構改善迴路式熱虹吸管蒸發端及冷凝端的液位差，同時採用較高熱傳導係數之奈米流體，以提升儲能效率。 以純水為工作流體之結果顯示，低充填量時，燒結管之平均儲能效率依不同加熱功率，較網格管提升約3%~7%，而網格管較平滑管提升約3%~10%；高充填量時，燒結管略優於網格管，而兩者皆優於平滑管約3%~9%，但當平滑管內沸騰模式由間歇性沸騰轉為核沸騰時，效率接近於網格管。燒結管、網格管及平滑管之最佳平均儲能效率各為37.80%、35.38%及33.30%；且最佳充填率在42.9%至48.6%之間。以粒徑約30奈米、重量百分濃度為0.5%之Al2O3奈米流體為工作流體時，對平滑管及網格管而言，平均儲能效率與使用純水時相近；對燒結管而言，低功率時（5W）約能提升5.86%~8.47%。
並列摘要
The energy storage system has been widely researched and used in recent years due to the energy crisis and environment protection. The development of energy storage system can help to collect the natural energy such as solar energy, or recycle the excess heat generated from the industrial processes. The loop heat pipe employs the phase-change mechanism, and hence has better efficiency. Loop heat pipes are not only cheap and easy to get, its passive design also makes it more reliable. Thus a loop heat pipe is used in our energy storage system. The liquid inside the evaporation tube will absorb the energy transferred from the heat source and becomes vapor, then moves toward the condenser and releases the latent heat into the water inside the energy storage tank. In our experiments, smooth, sintered and meshed copper tubes were used as different evaporation tubes. Other parameters were the fill-ratio of the system, power input, and different working fluids, inclusive of pure water and Al2O3 nanofluid (0.5wt%). Boiling characteristics and efficiencies are discussed. For the experiments with pure water as working fluids at low fill-ratio, results showed that the sintered tube had the best average energy storage efficiency, about 3%~7% better than meshed tube; and the meshed tube was 3%~10% better than smooth tube. At higher fill-ratio, the performances of sintered and meshed tubes were similar, but both were better than smooth tube about 3%~10%. When the nucleate boiling occurred in the smooth tube, its average efficiency became comparable to the meshed tube. The best average efficiencies of sintered, meshed and smooth tubes were 37.80%, 35.38%, and 33.30%, respectively. For the smooth and meshed tubes experiments with nanofluid as working fluids, results showed that the nanofluid did not aggressively enhance the average efficiency due to its higher superheat and late occasion of nucleate boiling characteristics. But it is able to enhance the efficiency for sintered tubes at low input power (5W) experiments about 5.86%~8.47%.