Closure to “Discussion of ‘Thermal Contact Resistance of Silicone Rubber to AISI 304 Contacts’ ” [ASME J. Heat Transfer, 122, p. 403 (2000)]

During tests of more than 40 hours at constant mechanical load (0.1214 MPa) and heater power (3.2 kW/m²), the resistances varied by less than ±2.5 percent after reaching steady state. There was no trend, either increasing or decreasing, in the values of the resistances. Surface profiles of the contacting surfaces were measured before and after the test and, as shown in Table 2 of 1, no significant difference was found in the surface profiles of the specimen. This indicates that, within the range of temperatures and mechanical loads tested, no significant changes in the surface characteristics occur during the duration of the test.

The thermal conductivity of the elastomer under investigation was measured before conducting the thermal contact resistance tests. Assuming a linear temperature distribution between adjacent thermocouples in an elastomer specimen, the thermal conductivity for the range of temperatures and mechanical loads to be tested was calculated using Fourier’s equation. The thermal conductivity of the elastomer is temperature-dependent, so care must be taken in calculating the bulk resistance from the thickness and thermal conductivity. Nevertheless, the bulk resistances calculated from the thickness and the measured thermal conductivity values agree well (±5 percent) with the bulk resistance obtained by subtracting the sum of the measured interface resistances from the total resistance of the joint. The details may be found in Parihar 2.

You are right, the units in Table 1 and 2 should read μm/μm.

Yes, at the lower interface the heat flow is from elastomer to metal.