Investigation on Cable Temperature in Wet Tunnel Considering Coupled Heat and Moisture Transfer

Abstract

Many elder tunnels often lack waterproofing facilities, and water can easily accumulate in tunnel bottom or even on cable surface. Using the finite element method (FEM), the three-dimensional tunnel cable model, which couples the fluid field, the heat transfer and the moisture transport, is developed in our study. The coupling effects especially the phase change behavior are comprehensively considered. It indicates that a high humid environment would benefit the heat dissipation. Depending on the initial vapor content, water distribution, and cable arrangement, the maximum cable temperature may drop to some extent ranging from 2 °C to 10 °C. The presence of water changes the thermal properties of air, including the thermal conductivity and heat capacity. The latent heat caused by evaporation accounts for a greater portion compared to conduction. The presence of water changes the vapor concentration distribution of tunnel. It is mainly located near the cable surface within a distance of 0.02 m, and it decreases drastically away from the cable. In addition to common radial heat transfer, both the longitudinal and circumferential heat flux exists arising from the movement of fluid flow and water evaporation.