Modelling of the heat transfer and fluid flow in a radio-frequency plasma torch with argon-hydrogen as the working gas

Abstract

Modelling results concerning the heat transfer and fluid flow in a radio-frequency plasma torch with argon and hydrogen as the working gas are presented. The diffusion of hydrogen in the gas mixture due to the presence of temperature and concentration gradients within the torch has been modelled by using the combined-diffusion-coefficient approach. Included in the modelling are also the effects of the induced currents appearing in the brass probe for central gas injection on the electromagnetic fields and thus on the plasma flow and heat transfer within the plasma torch. It has been shown that the electrical conductivity of the probe affects the modelling results of the flow field and the temperature distribution in the torch. The flow rate of the central argon flow has substantial effects on the temperature, velocity and concentration fields, especially in the region near the axis of the torch. Computed temperature profiles at a few cross sections of the torch are favourably compared with corresponding experimental data for a typical case.