Modeling of Radiative Transfer in Mercury-Argon HID DC Lamp

摘要

Radiative transfer is the most dominant mechanism for the energy transfer in UV source lamps operating at high pressure. The prediction of radiation transfer is one of the most important issues in the overall lamp modeling. Among the various models described in the literature, we have selected the P1 model initially developed to be used for a gray gas solution. We have adapted the model to be used with multiple bands and thus to simulate the radiation in the lamp enclosure. Our lamp consists of a thin glass wall enclosing a plasma. A 2d treatment of this problem is considered since the problem docs not depend on the azimuthal angle. The glass is semi-transparent so we deal with semi-transparent boundary conditions. Also, we assume that the incident radiation from within the medium is diffuse and the reflected component from wall interface is diffuse as well. Scattering is neglected. Finally, the reflected energy into the plasma is assumed to be small; therefore the calculation of exchange factor is not necessary. In our problem, the plasma medium is considered gray and consists of several bands with temperature dependent absorption properties. Within each band, a mean absorption coefficient has been calculated and it depends on the temperature and pressure and not on the wavelength (or frequency). Therefore we have derived a new formulation of the PI model that accounts for multiple frequency bands. Note that, the radiation intensity, through emission and temperature-dependant properties, depends on the temperature field and therefore cannot be decoupled form the overall energy equation. Thus the temperature field must be determined through an energy conservation equation that incorporates all three modes of heat transfer; conduction, convection and radiation.