CVD Reactors for coating fibers:

Chemical Vapor Deposition reactors are used to manufacture and/or coat fibers for use in composite materials We consider a cylindrical reactor where a carrier gas mixture of argon and oxygen enters and exits from its ends. The fiber is drawn continuously through the reactor and is heated by either heating the reactor walls or by external means such micro-wave or resisting heating heating. when the carrier gas flow stabilized small quatities of precursor gases are added to the mixture. Precursor molecules react on solid hot surfaces and deposit solid material that coats the surface. In Ideal situation one would want to coat the fibers not the reactor walls. Thus, cold wall reactors are most efficient. We model the gas flow as a compressible ideal gas with an energy equation including convection, conduction, and radiation in an axisymmetric reactor. The precursor species are modeled by convection-diffusion systems. Surface reactions rates are assumed proportional to the impingement rate and depends on temperature in an Arrhenius manner. Again adaptive software with Galerkin Least Square method was used to perform parameter studies and compare efficiencies of different reactors with varying geometry and operating conditions. In practical situations bundles of coated fibers are combined to form porous toes which are also coated in order to seal all pores between fibers which includes diffusion in porous media. Other interesting areas of research are modeling turbulent flow and multi-step chemical surface reactions and their effects on the quality of the coating.