This apparatus can be used for measuring the thermal conductivity of solids or to measure temperature drop across two mating surfaces using thin film interface materials. Heat is generated by electrical cartridge heaters on the top part of the apparatus continues through the test samples, and then into a water-cooled base. By insulating the rods, one dimensional, steady state heat flow is established in the samples.
For conductivity testing the heat first enters a sample of known conductivity then passes to the sample of unknown conductivity. By measuring the temperature at precise intervals in both specimens, it and relating the heat flow to the thermal conductivity, it is possible to find the conductivity of the unknown sample. The contact resistance of thermal interface materials can be found using a similar method. This test rig has been used recently to test new thermal interface materials created from mats of graphite nanofibers and to test the thermal properties of unique energy storage building materials.