4612 — Comparison of Four Models for Thermal Response Test Evaluation

Four two-variable parameter estimation models for evaluation of thermal response test data are compared when applied on the same temperature response data. Two models are based on line-source theory, the third model is a cylinder-source-based solution, and the fourth is a numerical one-dimensional finite difference model. The data sets contain measured temperature response, heat load, and undisturbed ground temperature from three thermal response tests, together with physical data of the tested borehole heat exchangers (BHE). The models estimate ground thermal conductivity and thermal resistance of the BHE and are compared regarding test length and data interval used. For the three defined data sets, the line source approximation model shows the closest agreement with the measured temperature response. The cylinder source and numerical models show sensitivity to the inclusion of early data. A recommended minimum response test duration of 50 hours is concluded from the model comparison.