Analysis of temperature variation in a geothermal borehole through TRT and cooling tests in the city of Talca, Chile

Abstract

On the San Miguel campus of the Catholic University of Maule, in the city of Talca (Chile), the conductivity and thermal resistance of a geothermal borehole were analyzed through a thermal response test (TRT) based on initial ignoring time (IIT) for 3 different heat injection tests, resulting in the thermal conductivity of at least 1.6 Wm-1K-1 and a thermal resistance of 0.25 mKW-1 (most unfavorable values). Taking advantage of the heating process through the TRT, the cooling capacity of the vertical geothermal heat exchanger was analyzed from a theoretical and practical point of view. Temperature profiles were obtained along the borehole at different time intervals through a water pressure and temperature sensor, and in this way, an average temperature curve of the borehole until the equilibrium temperature was obtained. The latter was compared with the theoretical curve of the cooling process. The results indicate that the cooling curves obtained in a practical way are similar to the theoretical curves. Together with this, a value for the thermal conductivity of 2.35 Wm-1K-1 was obtained.