Analysis of Thermal Conductivity of Borehole Heat Exchanger Measured During TRT Compared with Theoretically Calculated and Its Impact on the Installation Parameters

Abstract

To the proper system design using borehole heat exchanger is appropriate to implement thermal response test, which gives the averaged values, however, sufficient to quantify the performance of heat exchanger. Implementation of TRT is indicated for the site with very poorly recognized geological and hydrogeological conditions and the installation with greater power heat pumps i.e. over tens of kW heating/cooling. In such cases, the cost of the TRT can be paid back when the test result will show that the system can be made with less borehole heat exchangers than the designed based on tabular, averaged values of the thermal conductivity coefficient of the ground. The paper presents calculations for borehole heat exchanger installation for which thermal response test has been done in comparison with theoretical borehole heat exchanger selection model (based on literature data). Analysis of thermal conduction measured during TRT and theoretically calculated one, clearly indicate the amount of errors possible to commit during calculation and imprecise interpretation of literature data.