The thermal contact conductance (TCC) between two machined pieces of
stainless steel was studied. A guarded hot plate thermal conductivity test fixture was
designed and built for the experiment. Factors investigated included the contact pressure,
surface roughness, interface material and average test temperature. The contact pressure
at the interface ranged from 80 to 800 psi. The mean surface roughness of the opposing
surfaces was 2.8 ��in (.0708 ��m) parallel to the sanding direction and 1.9 ��in (.0482 ��m)
perpendicular to the sanding direction. Interface materials included air, indium foil,
copper foil, Teflon tape, silver filled paint and thermal grease. Average test temperatures
ranged from 0��C to 100��C, in 20��C increments.
With air alone in the interface gap the TCC was nearly insensitive to contact
pressure. The thermal grease and silver filled paint most increased the TCC over air
alone while being nearly insensitive to pressure. With indium foil the TCC was similar to
air, but improved somewhat with increasing pressure. With copper foil the TCC was
lower than air alone, but increased with increasing pressure. The Teflon tape had a lower
TCC than air at low contact pressure, but a higher TCC than air at higher pressures. In
general the TCC improved somewhat at higher temperatures. The ability of an interface
material to improve the TCC is more a function of its flow stress and wetting ability than
its thermal conductivity.
An existing mathematical model was used to predict the TCC with air as the
interface material, and was found to over-estimate the TCC by an order of magnitude. It
was found that the model did not accurately predict the effective surface spacing for very
smooth surfaces as used in this work. When a modification for smooth contact surfaces
was incorporated into the model it yielded results that were consistent with experimental
results. / Graduation date: 1999
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33742 |
| Date | 18 August 1998 |
| Creators | Schneider, Donald A. |
| Contributors | Wolff, Ernest G. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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