Numerical evaluation of effective emissivities of black-body cylindrical cavities
Vicente de Paulo Nicolau
A cylindrical cavity was simulated considering radiation exchange in the enclosure. The diffuse and gray surface model and the net-radiation method, based on Gebhart coefficients, were adopted. Herein, the influence of the length to diameter ratio, surface emissivity, discretization mesh and temperature profile of the cavity surface on total and spectral effective emissivities are examined. Some numerical results regarding the influence of the temperature profile show that a non-isothermal cylindrical cavity can be used as a good approximation of a black-body cavity. This is observed for a radiation beam originating from the cavity bottom, with a small solid angle around the cavity axis.
Keywords: Thermal radiation; black-body cavity; emissivity; effective emissivity; nonisothermal cavity; net-radiation method.