A small-scale experimental apparatus to study heat transfer in the vicinity of geothermal boreholes

This article reports on the design and construction of a small-scale laboratory tank to study transient heat transfer in innovative ground heat exchangers designs. The tank is 1.35 m high and has a diameter of 1.4 m. It is filled with well-characterized laboratory-grade sand and instrumented with precisely positioned thermocouples. Experimental results for a 73-h heat injection period followed by a 5-day recovery period for a single U-tube borehole are reported. A comparison is performed against results obtained with an axisymmetric numerical model of the ground surrounding the borehole. It is shown that the agreement between both set of results is very good indicating that accurate experimental data can be obtained with the apparatus.