半圓洞道內線性熱源位置對剖面溫度的效應

Effects of Position of Linear Heat Source on Cross-Section Temperature Distribution in a Semicircular Tunnel

劉彥宏(Yen-Hung Liu)

指導教授 ： 蘇金佳

國立臺灣大學/工學院/機械工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02256

摘要

大型地下洞道的發展和工程設計越來越普遍且受到重視，國內對於大型洞道工程的經驗不多，且缺乏相關的研究文獻，本研究以大型半圓洞道為實體模型進行研究，並利用冷水管間接冷卻系統作為洞道內的冷卻散熱裝置，以棒狀加熱器模擬洞道中因輸電發熱的電纜熱源，探討相關的熱傳效應。
　　實驗過程中以四個加熱器位置、加熱器表面溫度（100℃、150℃、200℃、250℃）、冷卻水總流量（8LPM、12LPM、16LPM）和冷水管數（四管、單管Ⅰ、單管Ⅳ）作為操縱變因，在洞道內佈設熱電偶線量測空氣溫度，同時也量測冷水入出口水溫及加熱器表面溫度，將所獲得的數據進行軸向溫度分佈、剖面溫度分佈的分析和繪圖。
　　當洞道內熱源置於越上方（但在冷水管位置以下）靠近冷水管時，雖然在洞道頂端的空氣溫度較熱源置於其他位置來得高，但熱源水平位置以下具有均勻且低溫的活動空間；若半圓洞道內熱源置於圓弧面中間或下方位置，雖然熱源附近的空氣受熱膨脹上升有較充裕的空間和洞道上方冷水管的冷空氣混合，使得洞道內最高溫降低，但在洞道剖面空間中大部份量測點的溫度則較熱源置於高處來得高。研究結果也顯示，在同樣的冷卻水流量和同樣的熱源表面溫度之下，若將熱源置於洞道不同的地方，除了會造成不同的剖面空氣溫度分佈之外，空氣平均溫度和最高最低溫也會出現差異。
　　而在冷水管數的研究中，發現在相同的冷水總流量之下，冷水管數多寡的均勻散佈程度對洞道內空氣溫度的高低影響非常顯著，冷水管採多管的分佈會比單管大流量大幅降低洞道空氣平均溫度和最高溫。
　　另外，在熱源所在水平線以上的溫度量測點，較易產生溫度變動的情形，尤以熱源正上方附近及冷水管下方周圍的變動區間最大，顯示該處冷熱空氣對流的劇烈及不穩定。

關鍵字

地下洞道 ； 間接水冷 ； 半圓形封閉空間 ； 自然對流

並列摘要

The development and engineering design of large underground tunnel becomes more general and worthy to take seriously. We don’t have enough engineering experience on building large underground tunnel in Taiwan and lack for the related research literature. This research proceeds in a large semicircular tunnel model, in which air is cooled by indirect water cooling system. The linear heat source in the tunnel is simulated by electric heaters.
　　The effect of the position of the heat source, the surface temperature of the heater(100, 150, 200, and 250℃), cold water flow rate(8, 12, and 16LPM), and the number of cooling pipes(four pipes, single pipeⅠ, single pipe Ⅳ) were investigated. Air temperature distribution in the tunnel in the axial direction and in different cross- section areas were obtained with thermocouples.
　　If the linear heat source is located near, but below, the cold water pipe located on top of the tunnel, the temperature of the air near the top of the tunnel gets higher. However, we have more uniform and lower air temperature in the tunnel space below the heat source. When the linear heat source is located in the middle section or near the bottom of the tunnel, the highest temperature of air reduces, but the average cross-section temperature becomes higher. Though the water flow rate and the surface temperature of the heater keep the same, different positions of the heat source cause different air temperature distribution in cross-section. The average, maxumin and minimum of air temperature were also change.
　　In the experiment of the number of cooling pipes, the result shows that using multi-pipe to reach the same water flow rate has lower temperature of air in tunnel than using single pipe.
　　Moreover, the temperature at the position above the level line of the linear heat source changes easily and oscillate, especially near the position right above the heat source and below the cool water pipe. It shows that the counter flow of cold and hot air there is most fierce and most unstable.

並列關鍵字

underground tunnel ； indirect water cooling ； semicircle enclosure ； natural convection

參考文獻

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