One-dimensional model of thermal radiation calorimeter for measuring thermal conductivity and thermal diffusivity

A new mathematical formulation and experimental conditions for thermal radiation calorimetry for the measurement of thermal conductivity and diffusivity are discussed. When an insulated plate sample is heated and cooled on the front surface and a radiant heat flux is emitted from the rear surface, the heat flux can be assumed to propagate in the thickness direction through the sample by one-dimensional heat conduction. On the basis of this assumption, the analysis by means of the Taylor series expansion shows that the thermal conductivity and diffusivity can be estimated from the temperatures and the ramp rates of both sample surfaces in heating and cooling modes, and the emissivity of the rear surface. The present formulation was tested by a computer simulation for several samples: Pyroceram9606, Pyrex7740, 5.3 wt% yttria-stabilized zirconia, alpha-Al2O3 in the temperature range 373.15-673.15 K, and polymethylmethacrylate in the range 273.15-373.15 K. The thermal conductivity and diffusivity estimated by the present formulation coincided satisfactorily with the original values used for the simulation.