Measurement of Soil Thermal Properties-Techniques and Instrumentation

A previous report[l] described the nature of thermal stability, which is by far the most difficult soil thermal property to measure since it is more a concept than a well-defined physical entity. This paper will describe improved methods and instrumentation for measuring thermal resistivity, thermal diffusivity, and thermal stability which have been developed in the course of EPRI-sponsored research which culminated with the development of a microprocessor controlled Thermal Property Analyser (TPA). As well, the context in which thermal stability is relevant to the design of underground transmission systems will be examined. In future papers, methods for determining statistically-based soil thermal design parameters from historical weather records and incorporating these improved techniques into underground thermal design will be discussed.