Effective emissivities of black-body cavities with grooved cylinders

The optical ray-tracing approach based on the Monte Carlo method was applied to evaluate the radiative characteristics of isothermal black-body cavities with reflectivities in the intermediate range between diffuse and specular reflection. The directional effective emissivities of the cylindro-cone cavities with rectangular- and triangular-grooved surfaces were calculated accurately enough for practical applications. The superiority of the cavities with grooved surfaces to those with flat surfaces can be indicated quantitatively in the specular-diffuse model. The effective emissivities of the triangular-grooved cavities are much higher than the rectangular-grooved cavites in this intermediate range between diffuse and specular reflection. The difference in radiative characteristics between triangular- and rectangular-grooved cavities can be explained qualitatively by the decrease in the fraction of the ray bundles associated with two reflections inside the cavity.