Thermal Performance Evaluation of Six Soils of Different Texture Classes

The objective of this research was to develop a Thermal Performance Index (TPI) which can be used to classify the ability of a soil type to transfer heat. The TPI must account for the relative magnitude of heat transfer along with the ability of the soil to sustain heat transfer under thermal load. Susceptibility to thermally-induced drying, shrinkage and reduction in thermal contact conductance at the heat exchanger-soil those factors interface are also important. Knowledge of which have the greatest affect [sic] on thermal performance can be used to determine what soil types make good backfill materials around buried heat exchangers. The following sub-objectives were identified to obtain the main objective: - Obtain thermal conductivity as a function of water content and dry density for six soil types of varied texture. - Identify the density and water content ranges at which each of the six soil types normally exist. - Perform a series of laboratory experiments to measure heat transfer rate and water content distributions in the six soils. These tests will consider the effect of soil density, initial water content and applied thermal gradient. - Rank the six soils according to their thermal properties and measured performance under thermal loading. - Utilize the available physical, thermal and water property data of each soil to develop a Thermal Performance Index that may be used to classify the ability of soil type to transfer heat