圓形洞道內單線性熱源對剖面溫度之效應

Abstract

對於人口密集度較高的地區，傳統高架電纜線對人類造成的危害逐漸增加，故高架電纜線地下化已經是時勢所趨，而地下纜線在輸送電力時，會產生大量的熱量，國內目前仍缺乏在如何將這些熱量排除之研究，因此本研究以一實體水泥洞道來模擬地下洞道、棒狀加熱器模擬電纜線發熱、以間接水冷的方式作為洞道內之冷卻系統。 實驗中之操作變因如下:五種冷水管位置(A、B、C、D、E)、室溫範圍(17℃~31.1℃)、加熱器位置(30ﾟ、120ﾟ)、加熱器功率700W、總冷水管流量7.5LPM、冷水管管數(雙管、三管、四管)。分別調整至所需條件後，以數個熱偶線量測洞道內某一剖面以及冷水出入口水溫，以溫度記錄器儲存數據，最後將各點數據加以繪圖及分析。 在不同室溫的情況下發現，當室溫越高，冷水管所帶走之熱量增加，壁面所散失之熱量減少，因此對於不同室溫，相同冷水管配置條件下，無法對冷水管最佳配置做判斷，必須以某一室溫範圍，使得剖面溫度變化不受到室溫之影響；在冷水管管數為三，加熱器位置為120ﾟ，固定某一室溫範圍下，得到冷水管最佳配置情況為ACE；冷水管管數為四，加熱器位置為120ﾟ及30ﾟ時，最佳配置分別為ACDE以及BCDE；接著對於不同室溫範圍，冷水管管數為四，得到相同之最佳配置。 最後因在多冰水管之實驗中，往往需要耗費相當多時間以得到所有數據，因此嘗試著以較少冷水管管數之實驗，來預測多冰水管之最佳配置，且以多組數據加以驗證。

In high population density areas, the risks from overhead electric cables to human health are increasing. As a result, replacing traditional overhead cables with underground cables are needed. However, the cables will produce large amount of heat in the underground tunnel. The research of cooling down the sewer system is still lacking in Taiwan. Therefore, this research utilizes a cement tube to simulate the environment of a sewer system, heat sticks which work as the cables in the system, and water for indirect cooling in the sewer system. Controls in the experiment are five positions of the water pipe in the cement tube (A, B, C, D, E), range of room temperature (17℃ to 31.1℃), site of the heat stick(30ﾟ and 120ﾟ), power of the stick - 700W, flow rate (7.5LPM), and the numbers of the pipe (two, three, four ). After these controls have been adjusted, thermocouple wires that are installed in the cement tube detect the temperature of three different sections: a random cross section, the entry, and the exit of the water pipe. We then analyze the plot which is built from the data from the sensors. In different room temperatures we found that the higher the room temperature the more heat the water pipe can cool, we also found that the heat which is dissipated by the air surrounding the tube is diminished. Thus, for different room temperatures and the same pipe placement, we cannot optimize the placement of the cooling pipes. It must remain within the certain range of room temperature, so the temperature which is measured from a random cross section will not be affected by room temperature. Within the specific temperature range, the number of pipes is three, the heat stick is placed approximately 120ﾟ from the top of the tube, and we found that the optimal positions of the pipes is ACE. We then changed the number of the pipe to four and placed heat sticks in position 120 and 30 degrees from the top of the tube. In this condition, the optimizations of four pipes are ACDE and BCDE. Next, we continue to place four pipes in the tube, but within different range of room temperatures. We got the same optimizations which are ACDE and BCDE. We used the data from the experiment which is using less pipes to simulate and prove the optimizations of multiple cooling pipes, because of the experiment which is utilizing multiple pipes needs to spend a lot time to obtain all data.