The calculation of the emissivity of cylindrical cavities giving near black-body radiation

A new calculation has been made of the emissivities of cylinders closed at one end and having in the other end an opening of radius either equal to or smaller than the radius of the cylinder. The results are presented for cylinders having diffusely reflecting walls with dimensions such that the emissivity is very close to unity. The method of calculation is that devised by de Vos, but fewer approximations are made, and significantly higher values of emissivity obtained. Comparison with the results of other calculations leads to the conclusion that those of both Buckley and Gouffe are seriously in error for this type of cavity while those of Sparrow et al. are in very close agreement with the present results though obtained by quite different methods. Estimates are made of the effects on the emissivity of internal baffles and grooved surfaces.