Fast segregation of thermal response functions in short-term for vertical ground heat exchangers

A detailed understanding of the short-term performance of the ground heat exchanger (GHE) is a major concern in the design of ground-source heat pumps (GSHP), as it has a significant impact in the efficiency and costs of the facility. The use of numerical models or artificial intelligence techniques may help in the short-term, although they are generally very time-consuming, becoming unpractical in numerous cases. The aim of this work is to obtain the thermal response factors according to the GHE, segregating the transient borehole behavior from the soil effect, based on a previous study which applies experimental data from thermal response tests (TRT) to the finite line source (FLS) model. The proposed method implies an extensive study of the fluid temperature as well as the development of new auxiliary thermal resistances related to the borehole and fluid, avoiding the implementation of numerical models. This procedure has been validated with the temperature outcomes of a 3D numerical model, obtaining low deviations, into a range of +/- 0.1 K, and mean absolute deviations below 0.01 K.