Geometrical differences of isotherms in convective high intensity discharge lamps

Summary form only given, as follows. It is known that convective effects in High Intensity Discharge (HID) Lamps play a significant role by transporting heat from the arc plasma core towards the arc tube walls. The effects of convection in a vertically operated HID lamp are studied via computer simulations and the results are presented. The governing equations, in the simulations, are the Navier-Stokes equations and Poisson´s equation; the latter allows for a volumetric Joule heating that is included in the energy equation. The transport coefficients of the gas are assumed to be those of a Hg and Ar mixture in an isobaric system. Radiation transport was not included in the simulations. The effects of convection on isothermal and isospeed surfaces at different locations within the gas are presented. The behavior of such isosurfaces with increasing arc tube diameter is also included.