CORRECTION FOR CALCULATION OF PARTICLE HEAT TRANSFER IN THERMAL PLASMAS

One of the most widespread areas of plasma technology is a treatment of fine-dispersed materials in plasma jets. Complexity of an experimental research of system "plasma flow - particles" has caused the creation of the mathematical models describing movement, heat transfer and physical and chemical transformations of dispersed materials in plasma. Researches of heat transfer in high-temperature flows are of significant interest as heat transfer from plasma to particles of powder is the determining factor. A number of studies of particle heat transfer in thermal plasmas give the following expression for Nusselt number: Nu=2+A·Re0.5·Pr0.33, where A is constant. However, this expression overestimates Nu in comparison with experimental data. In this connection authors offer the criterial expression for calculation of particle heat transfer in plasma taking into account the correction for conductive term: Nu=2·(Vs/Vp)+A·Re0.5·Pr0.33. Introduction of correction namely Vs/Vp obviously explains mechanism of influence of heat transfer conductive component on particle conductive-convective heat transfer in thermal plasma and result in sufficiently good agreement of calculations with numerous experimental data.