Analysis of interphase heat and mass transfer in suspension plasma spraying using air

Abstract

A theoretical model of interphase interaction “suspension particle - plasma flow” is proposed. The model assumes several successive stages of the evolution of liquid material: 0) entry into the plasma stream and break-up of the liquid into droplets; 1) heating the droplet to the evaporation temperature of the carrier fluid; 2) evaporation of the liquid, accompanied by convective mixing of the material; 3) evaporation of the liquid with the formation of a dry crust; 4) heating the solid material to melting; and 5) evaporation. Based on the analysis of the intensity of the processes of interfacial heat transfer, evaporation, diffusion and filtration mass transfer, relations are obtained for evaluating at each stage of the process duration, particle size, speed and distance passed in the flow. Demonstration calculations were performed for an aqueous ZrO2 suspension with a solid phase concentration of 20% injected into the air plasma stream at a flow velocity of 2000 m / s and a flow temperature of 5000 K.