ISSN: 0090-3973
Page Count: 7

Measurement of Apparent Thermal Conductivity by the Thermal Probe Method
Manohar, K
Lecturer, The University of the West Indies,

Yarbrough, DW
Professor, Tennessee Technological University, TN

Booth, JR
Adjunct professor, Tennessee Technological University, TN

Abstract

Three thermal probes were constructed in accordance with ASTM D 5334 and calibrated using heat-flow metre data. The temperature-time response of the thermal probes for determining apparent thermal conductivity λ under transient state conditions was logged at 1 s intervals. The instrumentation used reduced the determinate error associated with voltage and current measurements to a negligibly small value that made the uncertainty in λ dependent on the uncertainty of the slope dT/dlnt. A test method was run in 1000 s, in which a criterion of 2.5% spread among three consecutive slope values was used to determine the extent of the linear segment of the T–ln t curve.

The probes demonstrated repeatability within ±3.5% but had definite individual bias indicating a need for individual calibration. Using individual probe calibration factors, the experimentally de termined λs for all-purpose sand, sifted sand, and soil were deter mined to be 0.520, 0.445, and 2.11 W/moK, respectively.

Keywords:
thermal probe, thermal conductivity, line source method

Paper ID: JTE12123J
DOI: 10.1520/JTE12123J
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