Thermal performance and operating energy consumption of the energy tunnel system

Abstract Energy tunnels offer excellent heat exchange performance and high economic viability, making them particularly suitable for managing the loads of underground tunnels. In this study, 12 influencing variables were selected to systematically investigate the heat exchange performance and operational energy consumption of energy tunnel systems. A numerical heat transfer model was developed and simulated over a month period under both static and dynamic load conditions. Range analysis and analysis of variance(ANOVA) were employed to evaluate the effects of these 12 parameters on the coefficient of performance(COP) and operational energy consumption of the energy tunnel system, and to identify the optimal parameter combinations. The results show that, for the COP and operational energy consumption, the optimal levels of the influencing factors predominantly correspond to level 3. The average variation trends of the influencing factors for COP and operational energy consumption exhibit a high degree of similarity. Under both loading conditions, the lining material and the location of the heat exchangers within the lining exert significant and substantial effects on the COP and energy consumption. In contrast, the longitudinal length of the heat exchangers and the lining thickness have negligible influences on both performance indicators. These findings offer a valuable reference for the future design and implementation of energy tunnel systems.