Development of Thermal Conductivity Probes for Soils and Insulations

摘要

Eighteen laboratory-type and 3 field-type probes were designed, constructed and tested. Stainless steel, copper and plastic probe sheaths with epoxy resin, ceramic, or Wood's metal fillings were used with bifilar and single or multiple wire constantan heaters. Copper-constantan thermocouples and thermistors located both within the probe and on the probe sheath were used as temperature sensors. Probes from 0.020 in. to 1/4 in. in diam. and from 3 to 24 in. in length were used. The probes were laboratory tested in dry and moist silt, gravelly sand, beaded polystyrene, and Foam-glass insulations over the temperature range from -40 to +90F. Measurements were also made in snow, ice, insulation boards, dry and moist silt, and gravel. The results of the tests indicate that the design and construction of probes for measurements of thermal conductivity of soils and insulating materials can be based on theoretical considerations with reasonable assurance of good probe performance and that the probes are useful and valuable for laboratory and field measurements.