{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lecture3

# lecture3 - Numerical Example Quasi-steady State A cubic...

This preview shows pages 1–3. Sign up to view the full content.

Numerical Example – Quasi-steady State where c is in ppm and the hydrogen pressure, p H , is in atm. The density of steel is 7.73 g/cm 3 . The diffusion coefficient of hydrogen in steel is taken to be 10 -8 cm 2 /s. What is the rate of pressure drop (atm/s) as a result of diffusion of hydrogen through the wall? SOLUTION A cubic steel tank of volume 1 liter and wall thickness 0.1 cm is used to store hydrogen with an initial pressure of 8.7 atm. The tank is placed in outer space at 673 K. The hydrogen concentration on the steel surface is given by , H p c 3 = Diffusion Under an External Field v – velocity of mass flow or drift velocity under external force, F . v c x c D J + = Diffusion Mass flow or drift due to an external field MF = v where M is the atom mobility which is related to diffusivity through the Nernst-Einstein relation, T k D M B =

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Examples of External Forces, F ϕ – elastic potential - d ϕ /dx Elastic potential gradient γ – activity coefficient -k B Td ( ln γ ) /dx Gradient of excess chemical
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 5

lecture3 - Numerical Example Quasi-steady State A cubic...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online