A detailed kinetic model is applied to simulate the evaporation-pyrolysis of cellulosic material, a structured isotropic porous medium inside an electrically heated smoking article via ceramic heater. Heat and mass transfer in the flavor-generating cellulosic materials are coupled with moisture evaporation and precursor pyrolysis which are influenced by a strong interaction between transport phenomena and chemical reactions. A two-dimensional transient model is presented in this study to predict the physico-chemical processes of the pyrolysis and evaporation in the porous medium. This model considers pyrolysis of the cellulosic materials as obeying a kinetic scheme based on the functional groups (FG) and described with a single-step multi-reaction model, evaporation of water following a mass-transfer and rate-determined process. Physical processes involve the convection, conduction (including radiation if heat transfer) and the momentum resistivity due to the porous medium. In the study for momentum transfer, the Navier-Stokes equation including viscous loss and inertial loss is compared with a pressure evolution equation obtained through a combination of continuity, state and momentum equations. Moreover, in the case of energy balance, convective and conductive heat transfer rates at the boundaries are compared to figure out the relative importance of the different heat transfer mechanisms. This model is implemented in the commercial computational fluid dynamics (CFD) code, FLUENT, using user-defined-functions (UDFs).

Keywords: mathematical model, isotropic porous medium, multi-reaction, pyrolysis, ceramic heater