Effects of natural convection on the characteristics of long laminar argon plasma jets issuing upwards or downwards into ambient air-a numerical study

A modelling study has been performed on the effect of natural convection on the characteristics of a long laminar argon plasma jet issuing into ambient air. In this study the plasma jet is taken to be flowing vertically upwards or downwards, and the combined diffusion coefficient method has been used to treat the diffusion of ambient air into the argon plasma jet. It has been shown that although a temperature difference as large as 104 K is involved in the long laminar plasma jet system, in total the effect of natural convection on the fluid flow and heat/mass transfer within the plasma jet is small for the typical plasma jet parameters under study. Only at low jet inlet velocities and near the jet edge in the jet downstream region can the natural convection effect be detected