In Situ Measurement of Ground Thermal Conductivity Based on Analytical Solution Models

Determination of ground thermal properties is an important part of the design of ground-coupled heat pump system (GCHP). The number of boreholes and the depth and cost of each borehole are mainly dependent on the estimate of the ground thermal properties. This paper summarizes various determining method of ground thermal properties, the test apparatus, test procedure, theory basis and arithmetic on the in situ measurements of ground thermal properties based on analytical solution models are analyzed in detail, which includes the data curve-fit method based on the line heat source model and parameters estimation method based on the line heat source and cylindrical heat source model. The calculated precisions of the three methods are compared by an example calculation, the influence of test duration on calculated results is investigated. The results indicate that the estimate value of ground thermal conductivity by data-curve fit method is appreciably bigger than that by parameter estimation method and the calculated results are affected by the test duration.