A transient technique was validated for making thermal conductivity measurements. The technique incorporated a small, effectively spherical, heat source and temperature sensing probe. The actual thermal conductivity measurements lasted 30 seconds. After approximately 15 minutes of data reduction, a value for thermal conductivity was obtained. The probe yielded local thermal conductivity measurements. Spherical sample volumes less than 8 cm² were required for the materials tested. Thermal conductivity (and moisture) distributions can be measured for relatively dry or wetted samples.
The technique employs an encapsulated bead thermistor. A thermistor, more commonly used as a temperature transducer, has the inherent feature of being readily self-heated. A computer-based data acquisition and control system regulates the power supplied to the thermistor such that its self-heated temperature response approximates a step change. Thermal conductivity is deduced from the transient measurement of the power dissipated by the probe as a function of time.
The technique was used to measure the thermal conductivity of fifteen liquids and five insulation materials. Two different thermistor types, glass-encapsulated and Teflon-encapsulated, were evaluated. Capabilities and limitations of each probe type and the measurement technique, in general, were observed. / M.S.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/101183 |
| Date | January 1987 |
| Creators | Dougherty, Brian P. |
| Contributors | Mechanical Engineering |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | xiii, 118 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 17605183 |
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