Calculations of the average normal effective emissivity for nonaxisymmetric cavities using the modified finite volume method

Abstract

The average normal effective emissivity is widely used for calibration since it depends only on the intrinsic cavity characteristics; thus, it is an important parameter for blackbody designs and evaluations. Nonaxisymmetric cavities are widely used as standard blackbody sources and cryogenic solar absolute radiometers. The finite volume method is modified by adding a black-hole cylindrical extension to extend the integrated effective emissivity computations to the much more complex computations of average normal effective emissivities for nonaxisymmetric cavities. The calculated results using the modified finite volume method have an average relative difference of 0.085% from the Monte Carlo method, which is the only reported method for average normal effective emissivities of nonaxisymmetric cavities. The results show that this method can be used effectively for calculating the average normal effective emissivities of cavities with complex geometries.