18 May 2017

P.2.7.11 The effects of test temperature and duration on the results of constant temperature thermal response test


Constant heat flux method is commonly used for Thermal Response Tests (TRT) to predict the thermal properties of a borehole heat exchanger (BHE). An alternative method for TRT is based on constant temperature. Although the cost of this method is relatively higher than that of constant heat flux method, it provides better accuracy and shorter test duration besides well matching with the test standards of heat pumps. The aim of this study is to investigate the effects of test temperature and duration on the long-term predictions based on constant temperature TRT. By using different test durations and fluid temperatures, thermal properties of ground are calculated based on TRT data. Long-term heat transfer rates per unit length of a BHE (unit HTR) are predicted by using the calculated properties of ground. The relative differences between the predictions are compared with each other to examine the dependencies of the predicted unit HTR values on test temperature and duration. The results can be used to determine the suitable and practical duration and fluid temperatures for the applications of constant temperature TRT.