Pulsated Thermal Response Test experiments and modelling for ground thermal property estimation

Abstract

The Thermal Response Test (TRT) is a well known experimental technique for estimating both the ground thermal conductivity and the effective borehole heat exchangers (BHE) resistance in ground coupled heat pump (GCHP) applications. The usual experimental approach for the TRT measurements is to inject (and even extract) a constant heat rate in the ground while the carrier fluid is circulated inside a reference heat exchanger. In this paper the TRT approach is applied with reference to non constant heat rate condition during a several day measuring session at the SEB building site of the University of Genova, Italy. A constant heat injection has been operated for the first 100 hours of the experiment and then a series of 8 hour square pulses (on/off mode) have applied for about 11 days. The ground and BHE thermal properties have been here estimated according to different algorithms developed either at the University of Genova and Polytech Montreal, where either the ILS and FLS (Infinite and Finite Line Source) theories or a Resistance/Capacitance approach are implemented to reconstruct the measured temperature evolution from parameter estimation.