Hydrothermal interactions in energy walls

Energy geostructures (EGs) employ heat exchangers embedded in concrete geostructures, such as piles, walls, tunnels, and sewers. In this study, energy walls (EWs) are studied with an emphasis on the following objectives: (1) to understand the fundamentals of hydrothermal interactions acting in the vicinity of EWs caused by groundwater seepage in saturated soil; (2) to highlight hydraulically induced thermal effects and their consequences on the thermal performance of EWs. Extensive three-dimensional hydrothermal finite element analyses are performed considering two groundwater flow conditions: perpendicular and parallel to the EW. The thermal activation of the geostructure locally modifies the flownet with respect to the non-isothermal case because of the temperature dependency of the water properties. Mutual interactions between seepage directions and thermal activation are analyzed. Remarkable thermal interactions are detected within the heat exchangers. The thermal behavior of EGs is highly affected by an incorrect evaluation of the hydraulically induced thermal effects, which may result in an overestimation of the thermal behavior. Conversely, an efficient thermal design, which considers such interactions, may increase the thermal potential of EGs.