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Mass Transfer - Engineering

Q1:

Pick out the wrong statement.

A The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one.

B Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference.

C According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(b)P - 3, Q - 2

D The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz.

ANS:C - According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(b)P - 3, Q - 2

The wrong statement is: "The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one." The Reynolds analogy for mass transfer is not given by the Lewis relation, but by the Stanton number, and it is applicable when the Schmidt number is equal to one, not the other way around. The correct statement should be: "The Reynolds analogy for mass transfer is given by the Stanton relation and is applicable when Schmidt number is one." Therefore, the statement provided is incorrect.