A thermal-dissipation correction method for in-situ soil thermal response test: Experiment and simulation under multi-operation conditions

The in-situ thermal response test (TRT) is a key process to measure the soil thermal properties and has been widely applied for precise design and optimal operation of borehole heat exchanger (BHE). However, it is difficult to accurately calculate and simulate thermal dissipation from fluids to ambient air in test processes. This paper experimentally investigated geotechnical indoor testing and TRTs at 11 sites under multi-operation conditions. Furthermore, a thermal-dissipation correction method (TDCM) is introduced and established in TRNSYS to simulate the thermal dissipation. Infinite line source model (ILSM) and infinite cylindrical source model (ICSM) are adopted to comprehensively evaluate experimental and simulation results. The simulation results of TDCM are well verified and parallelly compared under multi-operation conditions. TDCM works well with ICSM on the correction of thermal resistance with improved accuracy over 10% and also improves the accuracy of average fluid temperature, soil thermal conductivities and heat flux per unit length of BHE. Besides, TDCM is more efficient to correct results processed with ICSM than that with ILSM and is valid for simulations with heating powers of 4–8 kW. This study proposes an efficient model to estimate thermal dissipation of fluids in TRTs and select appropriate operating parameters of BHEs.