The Pellet Transport Properties subnode to the Reactive Pellet Bed is used to specify fluid flow properties and diffusion coefficients within the reactive pellets.

From the Selection list, choose the domains on which the fluid flows through.

Select density, dynamic viscosity and permeability from the Fluid density, Dynamic viscosity, and Permeability lists, respectively. For both Fluid density and Dynamic viscosity, the density and viscosity from Chemistry could be available in these lists. If there are more than two different pellets, the fluid properties can be set to the same for all pellets by selecting All pellets from the Individual or all pellets list, or set for each pellet separately by selecting Individual (s).

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.

Enter the thermal diffusion coefficients for different species if there is any temperature change within the pellet. The temperature could be coupled to a temperature field solved by a Heat Transfer interface on the same pellet. This can be done by selecting corresponding temperature from Pellet temperature list in settings window of Reactive Pellet Bed feature.