Effect of Single Linear Heat Source on Cross-Section Temperature Distribution in a Circular Tunnel
Date Issued
2011
Date
2011
Author(s)
Chang, Yung-Chia
Abstract
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.
Subjects
natural convection
circular enclosure
underground tunnel
indirect water cooling
single linear heat source
SDGs
Type
thesis
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