Fundamentals of Mass Transfer

When concentration gradients exist in a multicomponent system, there is a natural tendency for the concentration differences to be reduced and, ultimately, eliminated by mass transfer. This is the process of diffusion, and mass transfer occurs by molecular means. Thus, water evaporates from an open dish and increases the humidity of the air. However, the rate of mass transfer can be increased by blowing air past the dish. This is called convective mass tranter or mass transfer due to flow. 

The basic equation governing the rate of mass transfer of component A in a binary mixture of A and B is (in one dimension) given by 

Although Eq. (13.2.1) is similar in form to Fourier s law of heat conduction and Newton s law of viscosity, the similarity is somewhat superficial. This is because the flux given by Eq. (13.2.1) is not relative to a set of axes that are fixed in space, but are relative to the molar average velocity that is, 

Because the molar flux of A relative to the fixed axes, is this 

If we choose to work in terms of mass units, the corresponding form of Eq. (13.2.1) is as follows [11]  

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The lack of adequate predictive models is an obstacle to industrial applications. The poor understanding of the fundamentals of mass transfer in biological cellular structures—a problem common even to other areas of food processing dealing with transport phenomena—is the main hindrance... 

APPLICATION OF THE FUNDAMENTALS OF MASS TRANSFER TO PLATE EFFICIENCIES... 

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