Examination of Thermal Diffusivity Measurement Method of Sample in Contact with Transparent Plate by Flash Method Considering Thermal Radiation
2020 Volume 34 Issue 4 Pages 117-128
Details
2020 Volume 34 Issue 4 Pages 117-128
As a measuring method by flash method of the contact pressure dependence of interlayer thermal resistance of 2 layered sample, there is a method of sandwiching the sample with transparent materials. In this case, the interlayer thermal resistance analysis is performed assuming that the heating light is absorbed by the sample surface and the radiant heat flux is proportional to the sample rear surface temperature and the sample and the transparent materials are in a thermally insulated state. Actually, there is a thermal contact between the sample and the transparent materials, so the influence on the measurement due to this contact can be considered. To evaluate this effect, 2-layer model (the opaque sample/transparent material) is assumed and the radiant heat flux from the rear surface of 2-layer material was studied when the surface of the material was pulse-heated. When the optical thickness of the transparent layer is about 0.1 or less and the product of the ratio of the 1st layer characteristic time to the 2nd layer characteristic time and the ratio of the 2nd layer heat capacity to 1st layer heat capacity is 0.5 or less, it was confirmed that 1st layer thermal diffusivity can be obtained with an accuracy of about 5% by the half-time method. In addition, it seems that it is desirable to use data about 5 times the characteristic time of the sample, because it is affected by the transparent layer later in the measurement time.
