Fig. 9From: Temperature sensor module for groundwater flow detection around borehole heat exchangersTemperature development during the cooling (a) and the relaxation phase (b) at the inner (black) and outer rings (gray) of the TSM for the sandbox experiment without (ground)water flow. The BHE fluid had a temperature of 10 °C, while the ambient temperature in the laboratory was approximately 20 °CBack to article page