Combined Diffusion and Convection Mass Transport

The total or absolute transport is the sum of diffusive transport and convective transport 

Substituting Equation 6.63 into equation, we arrive at an alternative form of the total molar transport flux cf species i 

Note that the diffusive molar flux given by Ficks s law can also be expressed in terms of fhe diffusion velocity of the species relative to the mixture molar average velocity. 

Mass transport owing to combined multicomponent diffusion and convection is written by combining Equations 6.57 and 6.60 as 

For lower temperature gradient and negligible diffusion thermal effect, a simplified form is written as 

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