Porous Media Diffusion
The Porous Media Diffusion subnode to the Reactive Pellet Bed is used to specify diffusion properties within the reactive pellets.
Domain Selection
From the Selection list, choose the domains on which the mass transport by diffusion takes place.
Several diffusion nodes can be used to account for different diffusion processes in different porous parts for the modeling geometry.
Diffusion
Select Diffusion model — Millington and Quirk model (the default), Bruggeman model, Tortuosity model, or User defined to describe the effective correction of the diffusion coefficient in the pellet. In the case of the Tortuosity model, a value for the tortuosity τpe within the pellet is required. Use this section to specify diffusion models and diffusion coefficients inside the reactive pellet.
From the Diffusion coefficient list, select diffusion coefficient for different species. If a User defined diffusion model is selected, an Effective diffusion coefficient Dpeff,c (SI unit: m2/s) is entered. The default value is 1·10-9 m2/s in both cases.
Diffusion coefficients calculated in Chemistry are available in the list when Chemistry is coupled to the Reactive Pellet Bed feature.