| A method is proposed to determine deep ground thermal properties at worksites using one-dimensional solid cylindrical heat source model together with parameter estimation method. The solid cylindrical heat source model considers the inner borehole of a vertical buried loop of Ground Heat Exchanger (GHE) as a solid and heat flux is imposed on the borehole wall, so it is more approximate than the hollow cylindrical heat source model which assumes the inner borehole has no mass, and also more approximate than the line source model which regards the buried U tube as a line heat source with a diameter of zero. And an analysis software is developed using this method to analyze the field test data. The software includes two parts:friendly human-machine interface and computation program, which respectively are written by Visual Basic and Visual C++. The software takes into account all aspects of the analysis of field test data, including parameter settingã€data readingã€calculation results and curve shows. So that users can easily carry out the data analysis operation and obtain the ground thermal properties. This paper has used the solid cylindrical heat source model, together with the parameter estimation method, to measure and analyze the ground thermal properties of some actual projects in situ, and the results show that this method can get credible ground thermal properties, which can be used for engineering design.The line source modelã€hollow cylindrical heat source model and solid cylindrical heat source model have respectively used to analyze the impact of measuring time on the ground thermal conductivity. The results show that when the test results achieves stable, the measuring time with solid cylindrical heat source model is shorter than that with the other two models. In addition, in-situ ground thermal properties measurement time of about48hours is relatively short to obtain stable ground thermal properties. The test time should be extend in order to obtain more accurate and reliable results. |
