Analysis of Thermal Response Test in Tianjin, China

Abstract

Thermal response test, a method to determine ground thermal properties for BHE?borehole heat exchanger?, this in-situ method for ground-source heat pump systems has spread to many countries where borehole BHE is used on a large scale. In this paper, in-situ thermal response test have been carried out in Tianjin University of Technology, China for double U-pipe with 32 mm pipe diameter. Boreholes are drilled in Sandy clay to a depth of 120 m and fitted with sand mixture filled U pipes. The test gives reliable design data by estimating the thermal properties of ground and boreholes. Underground temperature was determined to be 14.7 °C. A constant heat injection and extraction are imposed on two test boreholes during thermal response test, average heat and cold output is 35.41 kW and 78.79 kW, respectively. Simulation results based on linear source model agree well with the measure temperature response when the unstable data in first ten hours are excluded. These effects have proved to be of very important to the thermal performance of borehole thermal energy storage systems.