Improved p(t)-linear Average Method for Ground Thermal Properties Estimation during in-situ Thermal Response Test

One potential problem for the ground coupled heat pump is that the ground thermal properties is hardly to be known due to the complicated ground construction. The p(t)-linear average method has been proved that it can improve the accuracy of borehole thermal resistance. However, the p(t)-linear fluid temperature distribution approximation is not agree well with the temperature profile measured by the fiber cable. Thus, in this paper, an improved p(t)-linear average method in which the fluid temperature distribution approximation based on the vertical temperature profile is proposed. With the new vertical temperature profile simulation model, the accuracy for the borehole thermal resistance estimation will be improved comparing to the true value. Besides that, the estimation results are sensitive with the distance between two pipes, and together with the borehole thermal resistance, the distance will be optimized by the outlet fluid temperature. The life cycle cost analysis results of a case study for an office building in Hunan University show that, although the operation cost will be increased, the total cost during the whole lifetime will be reduced with a lower initial investment.