Criteria for accurate measurement of thermal diffusivity of solids using the Angstrom method

This paper presents criteria for accurately measuring the thermal diffusivity of a solid material using the Ångström method. In this technique, a periodic heat load is supplied at one end of the sample and temperatures are measured at different locations along the sample. The thermal diffusivity is estimated from the measured amplitude and phase of the temperature oscillations at various locations along the sample. Criteria are presented for important measurement parameters namely as periodic heat load power, waveform and frequency. Since more than two sensors are used, the accuracy is further improved since the linearity of the phase and amplitude data can be verified. We experimentally establish that a sinusoidal input heat load with a frequency as defined by the criteria established in this paper results in improved measurement accuracy. Based on these criteria, the experiment was performed with a range of materials spanning low to high thermal diffusivities namely Teflon, G10, Titanium Alloy (Ti6Al4V), Stainless steel (SS316) and Aluminium Alloy (Al6061-T6). The results indicate that the measured thermal diffusivity values deviate from the literature data at room temperature by less than 2.1%.