A new method for the determination of thermal conductivity and thermal diffusivity from linear heat source measurements

Abstract

The new algorithm of the thermal conductivity and thermal diffusivity determination from the transient hot-wire method has been applied to measurements performed in several solid materials. The algorithm makes use of the exact formula for the temperature variations, instead of its simple, asymptotic form that has been employed earlier. In the process of the least-square optimization of the residual function three parameters are obtained; thermal conductivity, thermal diffusivity, and the initial temperature. Two different variants of the method are presented: the classical one with the power kept constant during the measurements and the newly introduced constant current technique. The latter one has an advantage of requiring simpler conditioning electronics, and can therefore be recommended in space applications. The results of data processing show that thermal conductivity can be reliably determined even from the nonasymptotic part of the temperature measurements. The determination of thermal diffusivity is more difficult and requires high quality temperature data from the whole measurement interval.