The Effect of the Surrounding Medium and Its Pressure on Data Obtained in Thermal Diffusivity Measurements Using the Flash Method

This work describes experimental measurements made with a high temperature– high pressure flash thermal diffusivity instrument, using nitrogen, argon, and helium as environment. Data was generated using pressures from vacuum to 30 bar in the temperature range of ambient to 1000°C. NIST SRM 8425 (Poco AXM 5Q, fine grain graphite) was used for the tests. A total of 2.970 data points were obtained, showing a clear and prominent shift in the data, depending on the pressure and the thermal properties of the surrounding gas. Preliminary conclusions drawn from the work indicate the influence of heat conduction, convection, and diffusion through the environmental gas, on the thermal diffusivity results.