Temperature and Finite Pulse-Time Effects in the Flash Method for Measuring Thermal Diffusivity

TLDR

The flash method’s applicability spans the original Parker, Jenkins, and Abbott regime and a low‑temperature.

Abstract

The flash technique for measuring thermal diffusivity is analyzed for the case of a cylindrical-shaped specimen of radius r0 and thickness a to determine the effects of radiation at high temperatures, finite duration of the heat pulse, and the feasibility of low temperature measurements. It is found that the flash diffusivity method is useful in two complementary limits: (1) pulse time τ short compared to the characteristic thermal response time tc, (2) τ/tc of the order 1 to 10. The former case corresponds to the original description of Parker, Jenkins, and Abbott, while the latter case is suitable at very low temperatures. Moreover, it is shown that there is an optimum specimen thickness a for a given material and pulse time τ, in the sense that a higher temperature can be reached before any corrections have to be made to the Parker et al. analysis.