High Velocity Flows Inside Tube Reactors

Tube reactors used for the chemical vapor deposition of graphene and other 2D films on metal foils are typically operated at ambient pressures or under low vacuum (> 0.1 torr) and at low average flow velocities (< ~1-2 m/s) and Reynolds numbers (< 100). Thus, the flow inside the reactor is laminar and highly diffusive. This report explores what may happen if high velocity flows are instead used, by simulating reactor conditions with the Computational Fluid Dynamics toolbox OpenFOAM. High velocity flows with large Reynolds numbers were found to be turbulent and without any buoyancy driven recirculation. Additionally, a large cooling effect was observed with foil and gas temperatures much lower than the furnace set point. Finally, the temperatures of the 50-100 μm thick metal foils were not uniform but had large temperature gradients sensitive to the system pressure, the total mass flow rate and the process gas composition that increased with decreasing foil thickness.