地下電纜洞道溫度模擬與最佳化冰水管徑設計分析

Abstract

為了確保地下電纜洞道輸電系統的有效運行及其長期穩定性，本文專注於地下電纜洞道的散熱問題。考慮到台灣位於亞熱帶地區，夏季氣候相對炎熱，地下電纜極易因高溫過熱而影響其輸電效率與壽命。因此，本研究建立一套數學理論模型，用於分析並優化地下電纜洞道的冷卻系統，目的在於提升散熱效率和降低能源消耗，同時兼顧生命週期成本，以確保冷卻系統的經濟性。 本研究首先回顧地下電纜洞道的基本結構與運作原理，分析電纜在電流流經時產生熱量的過程。進一步，通過文獻綜述，檢視先前在地下電纜散熱方面的研究。在數學模型的建立階段，本研究以能量守恆定律和熱傳導理論為基礎，構建了一套描述洞道內空氣溫度變化及冷卻系統性能的數學模型，並與實際案例進行理論驗證以確認模型的準確性。分析結果顯示，冰水管的尺寸對洞道內空氣溫度有明顯影響。在相同的環境條件下，將冰水管徑從110mm增至180mm，可以使洞道內空氣溫度降低約5°C至6°C。進一步的耗能分析顯示，透過調整冰水主機的進水溫度和管徑尺寸，能有效控制整體能耗，在相同外部氣溫下展現最高40%的能耗差異。 最終，本研究提出了一種最佳化的冰水管尺寸設計方法，旨在冷卻效能和運行成本之間達到平衡。這方法以冰水管的生命週期成本作為目標函數。案例分析結果顯示，管徑為180mm的設計雖然初期設置成本較高，但其長期運行成本的節省，可以有效彌補初期投資的費用，從而展現出最優的生命週期成本效益。

To ensure the effective operation and long-term stability of underground cable tunnel transmission systems, this study focuses on the thermal management of underground cable tunnels. Considering Taiwan’s subtropical climate, where summers are relatively hot, underground cables are prone to overheating, which can affect their transmission efficiency and lifespan. Therefore, this research establishes a mathematical theoretical model to analyze and optimize the cooling system of underground cable tunnels. The aim is to enhance cooling efficiency and reduce energy consumption while considering life cycle costs to ensure the cooling system’s economic viability. This study initially examines the structural and operational fundamentals of underground cable tunnels with an analysis of heat generation when current flows through the cables. A subsequent literature review explores existing research on cable heat dissipation. During model development, a mathematical framework describing air temperature variations and cooling system performance, based on energy conservation and heat conduction theories, is constructed. The model’s accuracy is validated against actual case studies. The analysis results indicate that the size of chilled water pipes significantly affects the air temperature within the tunnel. Under identical environmental conditions, increasing the pipe diameter from 110mm to 180mm can reduce the tunnel air temperature by approximately 5°C to 6°C. Further energy consumption analysis shows that adjusting the chilled water main machine’s inlet water temperature and pipe diameter can effectively control overall energy consumption, demonstrating up to a 40% difference in energy consumption under the same external temperature. Finally, the study proposes an optimized design method for the chilled water pipe size to balance cooling efficiency and operating costs. This method uses the life cycle cost of the chilled water pipes as the objective function. Case analysis results indicate that although the design with a pipe diameter of 180mm has a higher initial setup cost, the long-term operational cost savings can effectively offset the initial investment, thus demonstrating the optimal life cycle cost efficiency.