Numerical comparison between two advanced HGHEs

Several solutions are currently being tested to improve the thermal efficiency of ground heat exchangers (GHEs) employed in geothermal closed loops. For shallow exchangers, the main effort is towards maximizing the surface available for heat exchange, while reducing the interference among exchangers; popular solutions towards this end are the slinky coil and the radiator shape. Recently, the flat panel has been proposed as a novel alternative to horizontal exchangers. In this study, the performance and thermal impact of the radiator and flat panel installations are compared by solving the transient flow and heat transport problem within the surrounding ground via a numerical model. Adopting the same computational conditions, the two installations yield different resulting domain thermal fields. The flat panel shows a higher capability to affect larger volumes of surrounding ground, so the soil temperatures reach values less extreme than in the radiator case. Since horizontal GHE temperatures remain 2–3° warmer in winter time, a higher coefficient of performance is expected for the flat panel.