A study of the convective flow as a function of external parameters in high-pressure mercury lamps

This paper deals with the modelling of the convection processes in high-pressure mercury arcs. Temperature and velocity fields have been calculated by using a 2D semi-implicit finite-element scheme for the solution of conservation equations relative to mass, momentum and energy. After validation, this model was applied to the study of the influence of are external parameters such as mercury charge and tube diameter on the convective processes. It was found that stable laminar mono-cellular convection flow occurs at low values of tube diameter for a cylindrical burner and/or a low mercury charge. Finally, we considered in detail the region behind the electrodes, where an accumulation of mercury is observed. The evaluation of this amount of mercury 'trapped' in these regions is of prime importance fora good description of the distribution of mercury in the burner and for a correct evaluation of the total discharge pressure.