地下電纜洞道內冰水管間接冷卻系統之性能研究

The Study of An Indirect Cooling System for High-Voltage Electrical Cables In Underground Tunnels

杜文翔(Wen-Hsiang Tu)

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(2006年)

https://doi.org/10.6342/NTU.2006.01067

摘要

對於地下電力纜線來說，當纜線在輸送電流之時，由於纜線本身的電阻的緣故，局部能量會轉變為熱能形式散失，所以冷卻系統的設計，便成了解決地下電纜洞道散熱最主要的問題。
本實驗研究計畫將透過調查與統計的方式對各種冷卻系統分析比較，並依據過去之文獻，進一步推估未來可能之需求。實驗內容採用洞道內水管間接冷卻的方式，並依據相似定律來針對實際的洞道尺寸建立模型以進行洞道模擬實驗，沿著洞道入口對不同的洞道剖面量測各部位之洞道溫度、冰水管溫度及電纜導體溫度等地下洞道工程設計重要參數的變因加以探討，最後找出設計條件的參考數據。
結果顯示洞道內的溫度會隨著離洞道入口的距離增加而上升，並在入口處的上升幅度最為明顯，代表冰水管前段帶走的熱量較多，隨著冰水管溫度的上升，帶走的熱量便漸漸減少。至於單一剖面的溫度變化則由加熱器位置往上遞減，到洞道上方時受到冰水管附近的冷空氣影響，溫度沿著半圓壁面往下遞減，至洞道半圓壁面最低點溫度最低。冰水流量與洞道溫度有直接的影響，流量越慢，洞道內的溫度越低；冰水管數對洞道整體溫度的高低雖無明顯影響，但管數越多，洞道前後的溫度變化較為平緩，表示系統的熱傳效果較為平均。

關鍵字

地下洞道 ； 自然對流 ； 間接水冷

並列摘要

As far as underground high-voltage electrical cables are concerned, when the cables transmit electric current, a part of electric energy will transform into heat and then dissolve due to electric resistance from the cables themselves. Therefore, designs of cooling systems are the main concern when we try to solve the problem of heat dissipation in underground tunnels where high-voltage electrical cables are installed.
In this research we estimate further possible needs based on preceding literatures regarding several such cooling systems. An experimental apparatus is built to study the performance of an indirect cooling system which cooling water tubes are placed through an insulated tunnel. The modeled tunnel that we engage in the simulated tunnel experiment is set up according to similarity laws. At different sections of the tunnel, tests are conducted to measure temperatures of the tunnel, the cooling water tubes, and the electrical cable. The variables are analyzed and studied and references may then be obtained for an optimal design of an underground high-voltage electrical cable tunnel.
The result shows that the temperature in the tunnel rises in accordance with the increasing distance from the tunnel entrance. At the entrance of the tunnel, the rising degree of the tunnel’s temperature is the most significant. It indicates that the cooling water tubes in the front section of the tunnel take away heat more. The higher the cooling water tubes’ temperature get, the less heat they take away. As for temperature variation of a single section, the temperature drops compliant with the ascending position away from the heater. At the top part of the tunnel, affected by cold air close to the cooling water tubes, the temperature gets lower and lower around the semicircular wall of the tunnel. The temperature gradually drops to the lowest at the lowest point of the semicircular wall of the tunnel. Water-flow exerts a direct impact on the tunnel’s temperature. The slower the water-flow is, the lower the tunnel’s temperature gets. Though the number of cooling water tubes shows insignificant impact on tunnel’s temperature variation, the more the cooling water tubes are, the smoother the temperature distribution is in the front and rear sections of the tunnel. This indicates the heat transform of the cooling system is more even.

並列關鍵字

underground tunnel ； nature convection ； Indirect Cooling System

參考文獻

[10] 陳慶豐，“超高壓電纜地下洞道冷卻氣流模擬分析”， 國立臺北科技大學凍空調工程系碩士論文，民國93年

[12] I. Sezai and A. A. Mohamad, “Natural convection from a discrete heat source on the bottom of a horizontal enclosure ”, International Journal of Heat and Mass Transfer, Pages 2257-2266, 2000.

[13] Frank Kreith and Mark S. Bohn, “Principles of heat transfer” , p301~345, 1986.

[14 ] Bruce R. Munson, Donald F. Young and Theodore H. Okiishi, “FUNDAMENTALS OF FLUID MECHANICS”, ch 6, 1990.

參考文獻