Formation of dynamic and thermal boundary layers in a methane pyrolysis reactor with variable viscosity and thermal diffusivity
K.V. Kolotilkina, S.V. Zaitsev, E.V. Stefanyuk, V.A. Kudinov
Samara State Technical University, Samara, Russia
Abstract
Using the integral heat balance method, analytical solutions were obtained for the formation of dynamic and thermal boundary layers in a methane pyrolysis (thermal decomposition) reactor with variable viscosity and thermal diffusivity within these layers. It is shown that, on the inner surface of a metal reactor wall heated to 1000°C, a layer of stagnant gas forms due to high viscosity and thermal diffusivity, having the same temperature as the wall. Isotachs and isotherms in this layer are located perpendicular to the wall surface. In this case, boundary layers form at a certain distance from the wall, within which the velocity is practically zero and the temperature is equal to the wall temperature, significantly exceeding the gas temperature outside the boundary layers. In the near-wall layer of stagnant gas at high temperatures, intensive carbon formation (pyrolysis graphite) occurs, depositing on the reactor walls until the reactor flow cross-section is completely carbonized and the pyrolysis process stops.
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