Abstract
It has been recommended to carry out ther-mal response tests (TRT) for a period of minimum 48 hours when the measured data are used together with a linear approximation of Kelvin’s infinite fine source func-tion for heat transport in porous materials to estimate ap-parent thermal conductivity of the ground. Recently an asymptotic solution of the line source function has been proposed to reduce the estimation error. This study exam-ined the potential of the new solution to also reduce the TRT period, as the new solution in principle can be ap-plied to early (short-time) data. For this analysis, a one-dimensional convective-conductive heat transport equation was applied for the circulating fluid, and three-dimensional conductive heat transport equations were applied for the ground, the grout, and the heat exchangers, to simulate heat transport and exchange between circulating fluid and the ground during TRT. Fluid temperatures simulated un-der different conditions were then used to estimate appar-ent thermal conductivity using both the linear approxima-tion and the asymptotic solution of the line source function. Results showed that the TRT period can be reduced to less than 20 hours with an average error less than 5 % even in case of extreme thermal conductivity of grout, which can markedly affect early (short-time) TRT data. The con-clusion was confirmed when also using actual TRT data collected at ground source heat pump (GSHP) test sites at Tokyo University of Agriculture and Technology and Saitama University.
