Numerical investigation on work performance of the anti-freezing drainage system of tunnel utilizing TPCT

Abstract

More than 40 % of tunnels in the cold regions of China incur freezing damage due to the freezing of drainage systems. This study proposes antifreezing drainage system technology based on the two-phase closed thermosyphon (TPCT) to eliminate freezing damage. This technology utilizes shallow geothermal energy around the tunnel to eliminate freezing damage and offers high heating efficiency, automatic operation, low energy consumption, and low maintenance requirements. Moreover, it can be used alone or in combination with other antifreeze technologies. A heat transfer model of the system is developed to investigate the feasibility of this technology. The influence of parameters of the TPCT (position, working fluid, length, diameter, and spacing) on the ditch temperature was studied by numerical simulation. The results show that: (1) the new technology increases the lowest ditch temperature by 3.03–5.44 °C, which leads to the ditch temperature remaining consistently above 0 °C; (2) The temperature of the ditch with the TPCT installed on the outside is 149.3 % higher than that of the ditch with the thermosyphon installed at the bottom; (3) the antifreeze effect of the TPCT is weakly related to its working fluid type; (4) this effect increases with the length and diameter of TPCT and decreases with the TPCT spacing; (5) Thermal resistance of the TPCT is the primary influence on its performance and antifreeze effect; (6) Performance of the TPCT decreased by 8 %–18.3 % in 8 years and stabilized thereafter.