Thank you very much for solving this problem, I think I know the way to solve it

Question

Thank you very much for solving this problem, I think I know the way to solve it (wrote it below) but I am unsure.

Topic: Steady state diffusion

Problem statement:

You use the concentration equation above Cn to calculate the concentration on each side (Ca, Cb), then you use the

Diffusion coefficient equation below (where you use the D0 and Qd values given in the problem statement) to find D:

And then you use Fick's first law and plug in the values (like in the example problem below) to find the diffusion flux.

5.9 When a-iron is subjected to an atmosphere of nitrogen gas, the concentration of nitrogen in the iron, CN (in weight percent), is a function of hydrogen pressure, py,(in MPa), and ab solute temperature (T) according to 4.90 x 10-3 v exp (-37.6 kJ/mol) C RT Furthermore, the values of Do and Qd for this diffusion system are 3.0×10-7 m2/s and 76,150 J/mol, respectively. Consider a thin iron membrane 1.5 mm thick that is at 300°C Compute the diffusion flux through this mem- brane if the nitrogen pressure on one side of the membrane is 0.10 MPa (0.99 atm), and on the other side 5.0 MPa (49.3 atm).

Explanation / Answer

Your analysis is indeed right,

Plugging in the values, obtain values of

D as 3.37*10^(-14) m2/s,

Ca-Cb as -3.498*10^(-6) kg/m3,

Given thickness as 1.5*10^(-3) m

gives us value of J as 7.85*10^(-17) kg/m2-s

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