Effects of Position of Linear Heat Source on Cross-Section Temperature Distribution in a Semicircular Tunnel
Date Issued
2009
Date
2009
Author(s)
Liu, Yen-Hung
Abstract
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.
Subjects
underground tunnel
indirect water cooling
semicircle enclosure
natural convection
Type
thesis
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