Short-time thermal response test based on a 3-D numerical model

Abstract

To assist the design of ground heat exchangers the thermal response test method is usually performed. In its traditional version the thermal response test data are compared with the line source model solution to restore the soil thermal conductivity and the borehole thermal resistance. This approach requires that a steady-state thermal condition is approached and, consequently, it may need up to about 50 hours to be carried out. Promising approaches can be found within parameter estimation procedures supported by 3-D numerical tools. They allow the reduction of the test duration, since they perform a more realistic description of the system's behaviour especially in the early regime. In this paper, a versatile parameter estimation procedure based on a 3-D numerical model of a geothermal system is presented. The procedure is aimed to restore the value of both the soil thermal conductivity and the borehole thermal resistance, by using only the first few hours of the thermal response test data. The approach is validated by comparison with a medium-scale set of experimental laboratory data.