OP-II-3

PP-I-29NUMERICAL INVESTIGATION OF NANOPARTICLES TRANSFERTO THE WALL OF HIGH-TEMPERATURE REACTORKolesnikov A., Moropeng L.Tshwane University of Technology, Pretoria, South Africa, kolesnikova@tut.ac.zaInorganic nanopowders (particle size in the range 10-1000 nm) are findingsignificant applications in a number of new advanced technologies. One of theattractive methods of nanopowders manufacturing at high production rate (hundredsof kilograms per hour) is a high-temperature gas phase synthesis in plasmachemicalreactors or flame reactors [1,2].The direct gas phase chemical reaction of precursor vapor to form particles andthe ease of separation of the particulate products from the gas makehigh-temperature gas phase reactors an attractive device for control of particle sizedistribution, which is on of the most important characteristic of nanopowders.However, proper operation of reactors requires better understanding of the role ofvarious factors, affecting the formation of particle size distribution.Formation of nanoparticles can be considered in the following schematic manner.The gaseous precursors undergo homogeneous gas phase reactions formingcondensable products, whose transition to the solid or liquid phase is initiated byhomogeneous nucleation. Coagulation (coalescence) of nuclei and particlescontribute to the further development of the particle size and number concentration.In high-temperature reactor with cooled walls the coagulation occurs underconditions of high temperature gradients, inducing thermophoresis [3]. The presenceof turbulence in the flow also introduces turbophoresis. These two factors areresponsible for the nanoparticle transfer to the reactor’s wall. As a result ofthermophoretic and turbophoretic forces action, the particle number concentration ingas flow decreases, affecting the coagulation rate and further the particle sizedistribution.The objective of the present paper is to analyze spatially two-dimensional aerosoldynamics for the high-temperature gas phase process in which the size distributionfunction (and average size) vary both in axial and in radial directions in a tubularreactor. Particular attention is given to the influence of thermophoresis andturbophoresis. The developed mathematical 2D stationary model incorporating heat,mass, momentum transfer and aerosol dynamics was solved with the help of272