An inverse analysis for identifying parameters associated with thermal response tests by using an accurate asymptotic solution of Kelvin′s line source function and Powell′s conjugate gradient method, and its application

Abstract

Evaluating up to higher terms of power-series expansion of exponential integral E(X), which appears in Kelvin′s line source function used for analyzing data of thermal response test (TRT), leads to an asymptotic solution that closely corresponds to the exact solution. This quasi-exact solution is used together with Powell′s optimization method to inversely identify both of thermal conductivity and a parameter relating to volumetric heat capacity of soils. The proposed method was verified by applying to test cases and then satisfactory adopted to real field cases operated under different conditions. A method of activating early data of TRT made it possible to identify intrinsic thermal conductivity efficiently without introducting man-made evaluation errors and to reduce operation cost and duration for TRT.