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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.

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In order to enhance the energy efficiency of nonthermal plasma methods for volatile organic compound decomposition in a catalyst-hybrid plasma reactor, we used a Cu-Cr catalyst to dissociate ozone into active atomic oxygen species at low temperatures. We investigated the conditions necessary to obtain the synergetic effect in single-stage and two-stage combinations. The ozone decomposition catalyst was not effective for the reaction under plasma discharge in the single-stage combination. In the two-stage combination, the efficiency increased by increasing the amount of catalyst. Although the propensity of catalysts for active oxygen species formation from ozone decomposition is important for optimizing the reaction efficiency, the surface area is even more important. We conclude that ozone decomposition catalysts are more effective in the two-stage combination compared to the single-stage.

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