Thermal response test
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A thermal response test (TRT) is used to determine the thermal properties of the ground. There is no direct way to measure ground thermal conductivity and borehole thermal resistance. The TRT is vital for designing ground source heat pumps and seasonal thermal energy storage (STES) systems. A TRT is an indirect (in-situ) measurement method which is the simplest and most exact way to determine precise thermal properties (Gehlin 2002).[1] Thermal response tests were first suggested by Mogensen (1983) at an international conference in Stockholm.[2] Mogensen suggested a simple arrangement in which heat at constant power is injected into (or extracted from) a borehole while the borehole mean temperature is measured.
The system consists of a borehole, pipe system, circulation pump, a chiller or heater with constant power rate, and continuous logging of the inlet and outlet temperatures of the heat carrier fluid. The equipment is normally contained within a single unit for ease of transport and efficient use.[3] The thermal response data (i.e. temperature development in the borehole at a certain energy injection/extraction) allows estimation of the effective thermal conductivity of the ground and the thermal resistance of the borehole.