An analytical model to predict the temperature in subway-tunnels by coupling thermal mass and ventilation. (December 2021)

• Record Type: Journal Article
• Authors: Sun, Tingting; Luo, Zhiwen; Chay, Tim
• Is Part Of: Journal of building engineering. Volume 44(2021)
• Publication Date: 2021-12
• Subjects: Subway tunnels -- Heat transfer -- Thermal mass -- Ventilation -- Thermal coupling; Building -- Periodicals; 690.05
• DOI: 10.1016/j.jobe.2021.102564
• Languages: English
• ISSNs: 2352-7102

Abstract

Abstract: There is an increasing incidence of overheating in subway tunnels in recent years especially in old subways without air-conditioning e.g., London Underground. There is still lack of a clear understanding how tunnel-air temperature is determined by complex thermal processes in subway tunnels. In this study, a mathematical model that describes the thermal processes in deeply buried subway tunnels was developed. Analytical solution was derived by separating the solution into time-averaged component and periodic component. The results show that the time-averaged component of tunnel-air temperature will approach steady state as the time tends to infinity, which has a positive linear relation with internal heat-source and average ambient temperature. Active cooling or heat-recovery systems could soon become a necessity in subway tunnels due to both global warming and increasing internal heat generation. Compared with outdoor air, the amplitude of the tunnel-air temperature shows a significant reduction in the day period but not in the year period. The surrounding soil temperature will keep changing for thousands of years. This study offers a new physical insight to analyse and mitigate overheating in subway tunnels. Highlights: An analytical model for deeply buried subway tunnels is developed. The model can describe the interaction between complicated thermal processes. How important factors determine tunnel temperature is analyzed. Efficacious solutions to reduce tunnel-air temperature are discussed.