For an example of how to use the Reactive Pellet Bed, see the model example A Multiscale 3D Packed Bed Reactor, file path Chemical_Reaction_Engineering_Module/Reactors_with_Porous_Catalysts/packed_bed_reactor_3d
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The dependent variable c for each chemical species i represents the interstitial concentration (SI unit: mol/m3), that is, the physical concentration based on unit volume of fluid flowing between the pellets.
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εb is the bed porosity (SI unit: 1). It should be noted that the R term on the right side is per unit volume of bed, (SI unit: mol/(m3· s)).
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N is the number of pellets per unit volume of bed.
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Equally as in Equation 3-20, cpe is the interstitial (physical) species concentration in moles/m3 of fluid volume element inside the pore channel,
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Rpe is the reaction rate in moles/(m3· s) of pellet volume. It should be stressed that the user input of R is per unit volume of pellet.
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Continuous concentration: assuming that all resistance to mass transfer to/from the pellet is within the pellet and no resistance to pellet-fluid mass transfer is on the bulk fluid side. The concentration in the fluid will thus be equal to that in the pellet pore just at the pellet surface: . This constraint also automatically ensures flux continuity between the internal pellet domain and the free fluid domain through so-called reaction forces in the finite element formulation.
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Film resistance (mass flux): The flux of mass across the pellet-fluid interface into the pellet is possibly rate determined on the bulk fluid side by film resistance. The resistance is expressed in terms of a film mass transfer coefficient, hDi, such that:
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