Experimental setup to measure the heat-exchange processes by controlling thermal and hydraulic conditions

The design of a Borehole Heat Exchanger (BHE) is based on the evaluation of the thermal exchange capacity of the whole system constituted by the probes and the surrounding ground. The energy performance of a BHE mainly depends on the thermal properties of the sediments, the possible groundwater flow and the changes in the thermal gradient in the probe's surroundings due to the continuous heat exchange with the subsoil. The interpretation of the in-field applications is often difficult because in many instances the information needed is unavailable due to difficulties of in-field measurements. An experimental device was built in order to assess, under controlled conditions, the evolution in time and space of the energetic processes that occur between a thermal probe and the surrounding ground. A copper probe was placed into a soil control volume of 1m3 and 24 high precision temperature sensors were distributed inside this volume at different distances from the probe. The configuration of the experimental settings was built to allow alterations in terms of sediments, groundwater flow conditions, thermal probe properties and operations, in order to simulate different physical conditions and to better understand the complex physical processes involved. Another goal of the experimental research was to produce reliable experimental data that can be used for the calibration and set up of numerical models. This paper describes the experimental apparatus and two experiments performed in order to assess its capability to satisfy the design requirements.