A CFD study on a vertical chemical vapor deposition reactor for growing carbon nanofibers

A computational fluid dynamic (CFD) study has been carried out to simulate velocity, temperature, and concentration profiles in a vertical chemical vapor deposition (CVD) reactor used for growing carbon nanofibers (CNFs). CNFs were grown over activated carbon fibers (ACFs) wrapped over an especially designed perforated tube which was vertically mounted in the reactor. The numerical model analysis incorporated the conservation equations of momentum, energy, and species. Natural convection effects on the heat-transfer and the exothermic heat generation due to the decomposition of benzene were included. The model simulation results revealed that approximately uniform temperature and concentration profiles existed in the ACF-packed bed. In addition, multiple combinations of the heating length and the wall temperature of the reactor were possible to achieve the prescribed CVD temperature. Under the simulated CVD conditions, the present model predicted an average carbon deposition rate of 5 × 10⁻¹³ kg/m² s, which corresponded to the yield of ∼0.005 g of CNFs per g of ACFs. The simulation results of this study are important for the optimization of the CVD operating conditions to achieve a high and uniform CNF growth in the vertical reactor.