Development and Calibration of a Large-Scale Thermal Conductivity Probe

A large-scale probe has been developed for measuring the thermal conductivity of geomaterials. The large probe was designed to conduct tests on materials containing large particles, materials with high heterogeneity, and materials with high stiffness. The probe has dimensions of 680 mm length and 15.9 mm diameter and was constructed of stainless steel tubing. The probe operates on the principle of heating an infinite line source in an infinite medium. Initially, parametric evaluations were conducted to determine the operational and test conditions for the large probe, including power level, heating duration, and zone of heating influence. Then, tests were conducted on five homogeneous materials to calibrate the newly developed probe. Thermal conductivity measurements obtained using the large probe were compared with measurements obtained using a conventional small probe. A calibration curve was established for the large probe. In addition, the performance of the large probe was evaluated in two manufactured heterogeneous materials and a large particle material. The test program indicated that the large probe can be used effectively for determining thermal conductivity of geomaterials. This new probe may be suitable for large-scale laboratory testing and field investigations