MODELING OF THE HEAT-TRANSFER AND FLUID-FLOW IN A RADIOFREQUENCY PLASMA TORCH WITH ARGON-HYDROGEN AS THE WORKING GAS

Modelling results concerning the heat transfer and fluid flow in a rad io-frequency plasma torch with argon and hydrogen as the working gas a re presented. The diffusion of hydrogen in the gas mixture due to the presence of temperature and concentration gradients within the torch h as been modelled by using the combined-diffusion-coefficient approach. Included in the modelling are also the effects of the induced current s appearing in the brass probe for central gas injection on the electr omagnetic fields and thus on the plasma flow and heat transfer within the plasma torch. It has been shown that the electrical conductivity o f the probe affects the modelling results of the flow field and the te mperature distribution in the torch. The flow rate of the central argo n flow has substantial effects on the temperature, velocity and concen tration fields, especially in the region near the axis of the torch. C omputed temperature profiles at a few cross sections of the torch are favourably compared with corresponding experimental data for a typical case.