Performance and effects on the subsoil temperature of a thermo-active diaphragm wall

The purpose of this study is to evaluate the behaviour of a thermo-active diaphragm wall, comprised in the foundation structure of a building basement, from the perspective of both the geothermal energy exploitation and the influence on the soil temperature field. Finite element analyses have been carried out on a wall single segment equipped with a heat exchanger, to evaluate the influence parameters and to optimize the pipe position and layout. In addition, a transversal section of the building and surrounding soil has been considered to simulate the heat transfer process and investigate the effects of the heat exchangers on the soil temperature over the year (short term) and in the years (long term). The assumptions have been made of seasonal variation of the ground surface temperatures and heating/cooling operating mode of the geothermal system. From the results of the parametric numerical analyses, some comments can be drawn about the influence, on the heat transfer, of the fluid flow velocity and of the coil layout and length. The results show also to what extent the soil can be an effective heat storage mass, in case of dual heating-cooling operating mode or single heating or cooling mode.