Numerical simulation of the heat exchange performance of an internal heat source energy tunnel

This paper takes a heating power tunnel dug by the shield-driven method in Beijing as a representative of an energy tunnel with internal heat sources (referred to as a heating power energy tunnel). Through tests of a tunnel with a similarity ratio of 1:5 and three-dimensional numerical simulation, the effects of the thermal insulation layer and arrangements of the heat absorber pipes on tunnel heat exchange performance were studied. The study shows that the heat flux for the circumferential arrangement of absorber pipes is 16.96% higher than that for the longitudinal arrangement without thermal insulation layers. Furthermore, adding a thermal insulation layer onto the inner surface of the segmental lining effectively slows the transfer of internal heat into the segmental lining structure of the tunnel, thereby reducing thermal interference caused by changes in tunnel air temperature. Compared to the condition without the thermal insulation layer for the circumferential and longitudinal arrangements, the heat flux q120 increases by 4.27% and 8.80% under steady-state operation, respectively. These research findings may provide valuable guidance for the design and construction of the related energy tunnels.