Multicomponent Transport in Porous Catalysts

It can be viewed as a work-related term that increases the internal energy of the system, unless diffusion opposes the external force. This contribution vanishes for pure fluids (i.e., ji = 0). It also vanishes for multi-component mixtures when the external force field acts similarly on all components in the mixture (i.e., g, = g for 1 f A ) because the dif-fusional mass fluxes of all components with respect to the mass-average velocity sum to zero  

Steady-state analysis of coupled heat and mass transfer within the pores of catalytic pellets is based on simultaneous solution of the mass transfer equation  

Stoichiometry in the mass balance with diffnsion and chemical reaction indicates that 

Equation (27-17) and the thermal energy balance given by (27-15) are integrated over an arbitrary control volume V within the catalytic pores via Gauss s law  

These conditions on the diffusional mass flux and the molecular flux of thermal energy, the latter of which includes Fourier s law and the interdiffusional contribution, allow one to relate temperature and reactant molar density within the pellet. If n is the local coordinate measured in the direction of n, then equations (27-20) and (27-21) can be combined as follows  

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