要約

Recently a new experimental set up for measuring the directional spectral emittance has been developed. The both sides of packed bed sample are simultaneously heated with identical power laser beams (4kw, CO² 10.6 μm) and the isothermal condition in the medium is assumed. In this paper, the coupled conduction-radiation equations are considered to investigate the effect of the temperature non-uniformity on the calculated value of the emittance and to verify if the isothermal assumption is valid. It is shown that the gradient temperature in the medium can be non negligible depending on the thickness and on the sample extinction coefficient.