CHEM 3615H CHAP 20

In the case of liquids and solids we will in

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Unformatted text preview: ng the z- axis). The velocity gradient is also called the shear rate. In these three transport cases, we find that the flux (denoted by J) of some property (mass, energy or momentum) is proportional to a gradient (composition, temperature or velocity), where the proportionality constant is a materials characteristic or property (Diffusion Coefficient (D) for mass transfer, Coefficient of Thermal Conductivity (κ) for heat transfer, and Coefficient of Viscosity (η) for momentum transfer). J(matter) = - D (∂c/ ∂z) J(energy) = - κ (∂T/ ∂z) J(momentum) = - η (∂vx/ ∂z) For perfect gases, very similar expressions have been derived for D, κ, and η. D = (1/3) λ <c> κ = (1/3) λ <c> CVm (n/V) η = (1/3) λ <c> M (n/V) Transport processes occur obviously also for real gases, liquid and solids. However, in the...
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This note was uploaded on 01/26/2014 for the course CHEM 3615 taught by Professor Aresker during the Spring '07 term at Virginia Tech.

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