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Diffusion Through Sphere

diffusion sphere mass transfer

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#1 oiler1

oiler1

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Posted 13 September 2014 - 03:18 PM

Hydrogen gas at a pressure of 1.25 bar is contained in a thick-walled
neoprene rubber sphere which has inner and outer radii of 70 mm and
80 mm, respectively. The concentration of hydrogen at the outer surface of
the sphere is negligible and leakage is so small that steady-state conditions
can be assumed to occur for a long time. The solubility of hydrogen
in rubber is 2.37 × 10–3 kmol m–3 (bar)–1 and the diffusivity is
1.8 × 10–10 m2 s–1. Calculate the rate at which hydrogen escapes from the
sphere. (Assume the inner surface of rubber is saturated with hydrogen.)

 

r=radial

pi=3.14

D= Difusivity

C= Concentration

4*pi*r^2 = for a sphere

1.25 for the BarG

 

4*pi*r^2x1.8 × 10–10 m2 s–1*1.25*2.37 × 10–3 kmol m–3

1.14

 

16.32 * 2962.5 * 18000000000

1.14

 

763389473684210.52

 

 

My actual equation are attached in the photos, I dont know if Im way off here to calculate for a sphere.  Any comments or help welcomed.

 

Attached Files



#2 breizh

breizh

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Posted 14 September 2014 - 05:18 PM


oiler1 ,
Should be :
4*pi*r1*r2*Dab*( Ca1-Ca2)/(r2-r1)

with Ca = S*pa/22.414 ( Kmol solute/ m3 solid ), Ca2 # 0

Hope this helps

Breizh




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