A preliminary testing of a flat panel ground heat exchanger

An experimental setup is devised to investigate the behaviour of a novel type of a horizontal ground heat exchanger (HGHE). The prototype is named ‘flat panel’ and is coupled with a hydraulic closed loop in which warm water is circulating to express the cooling mode from a reversible-cycle heat pump. Several thermal sensors are employed in the experimental field to monitor the ground temperature distribution and the fluid. The behaviour was tested during the summer of 2011, in the continuous and discontinuous operating mode. The HGHE behaviour was monitored in dry and wet conditions; the latter were induced with a dedicated irrigation system. The heat power for the unit exchanging surface dropped down from 140 to 40 W per metre of trench, moving from the start-up to the last period, late in the summer. The minimum was achieved in very hot conditions after long time in the continuous operating mode. When the working mode was switched to discontinuous, the power increased quickly over 50 W/m. Finally, the soil temperature was significantly altered up to 3 m far from the exchanger, and without over-heating conditions at the soil surface. The flat panel was able to involve a large soil volume, and this behaviour in turn enables high-energy performance, at least in the cooling mode. Copyright , Oxford University Press.