Thermal performance of energy diaphragm wall (EDW) adjacent to air-conditioned space from the underground-engineering perspective

Abstract

Energy diaphragm wall (EDW) has attracted increasing interest owing to its high energy efficiency and low operating cost. Current research concerning EDWs has primarily focused on its utilization in underground tunnels and parking spaces. However, no underground-engineering-related research has been performed to investigate the heat interaction between the EDW and the adjacent air-conditioned space resulting in extra heat gain or loss from the wall surface. This study numerically analyzes EDW implementation adjacent to an air-conditioned space to evaluate its feasibility and thermal characteristics. Firstly, the influence of the buried pipe on the heat-transfer regulation of EDW and the indoor thermal load was investigated. Next, a comparison of heat exchange between the pipe in EDW and the full-buried pipe without the influence of air-conditioned space was conducted. Later, the inner surface heat flux of walls with/without the installation of heat exchangers is carried out. Besides, the influences of wall configuration, hydrogeological condition, pipe, and indoor air temperature on the overall heat transfer efficiency of the EDW was investigated. It is construed from the results that the pipe's cooling capacity in the EDW is 12.8 % lower than the scenario without adjacent air-conditioned space for a 360-h operational period, and the difference becomes larger with time. The wall's natural cooling capacity was reduced by 93.8 % due to the installation of buried pipes with an operation duration of 360 h. The parametric analysis in this investigation provides a reference for further implementing EDW in underground engineering with adjacent air-conditioned space.