Apparatus for dynamical thermal measurements of low-thermal diffusivity particulate materials at subambient temperatures

Abstract

Apparatus for measurement of thermal diffusivity of particulate matter in the temperature range of 10-300 K is described. The basis of the measurement is modulated radial heat flow into a cylindrical sample, with a relatively small temperature gradient. Data is analyzed by Fourier transformation, and thermal diffusivity is determined from both the phase lag and amplitude ratio of the temperature at various locations along the cross section of the cylinder. This apparatus was tested with solid benzene, and found to give measurements within +/- 30%, in accord with the error analysis. It is especially useful for the determination of low thermal diffusivity materials, in the range of 1 x 10(-8) to 5 x 10(-6) m(2) s(-1).