Application of linear superposition theory in successive thermal response tests without ground temperature recovery

The thermal response test is an important way to obtain underground thermal properties for the design of a ground-source heat pump system. In practice, two successive thermal response tests with different heating powers may be conducted in the same borehole. If the waiting time between the two tests is not long enough for the ground temperature to recover to the original ground temperature, the subsequent thermal response test may be affected by the residual ground temperature field of the initial test. In this case, there is an obvious deviation between the results computed using the conventional line source method for the two thermal response tests. In the current article, a new computational method, based on linear superposition theory, is proposed to solve the problem encountered in the situation described. With the proposed method, the thermal conductivity is computed for four sets of thermal response tests conducted on four boreholes located in different zones, and the results demonstrate the accura...