Influence of ground water flow on implementation of distributed thermal response test.

EU IPA project entitled Research and the promotion of use of shallow geothermal potential in Croatia includes research in eight characteristic regions throughout the country. In this project distributed thermal response test (DTRT) has been applied on 100 m deep borehole heat exchangers in 152 mm diameter borehole. Use of fiber-optic cable for distributed temperature sensing allows determination of vertical distribution of thermal properties as main output data. DTRT consists of three phases. In the first phase temperature is measured with no fluid circulation. -Next 48 hours fluid is circulated with imposed constant heat flux and in last phase thermal recovery of the ground is observed. While the second phase allows determination of thermal properties, the last phase gives indication about heat transport in ground layers. Thermal properties for one location are presented, together with influence of the groundwater flow on the conventional thermal response test and the effective values of the thermal properties obtained.