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Convective mass transfer from a sphere
Posted Nov 16, 2015, 11:24 p.m. EST Version 4.3 2 Replies
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Hi,
I am modelling time dependent convective mass transfer from a sphere into a fluid flowing past over it.
When I am simulating it, at time t=0 itself it is showing the concentration profile and after that the concentration is remaining constant and no further change is being observed with time.
I am modelling time dependent convective mass transfer from a sphere into a fluid flowing past over it.
When I am simulating it, at time t=0 itself it is showing the concentration profile and after that the concentration is remaining constant and no further change is being observed with time.
2 Replies Last Post Nov 17, 2015, 1:42 a.m. EST
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Posted:
9 years ago
Mass transfer from a sphere reaches steady-state rather rapidly, that's why. The steady-state concentration profile is
C(r) = Cb - (Cb - Cs)*(a/r)
where Cs and Cb are the surface and bulk concentrations, respectively, and a is the sphere radius, and r is the distance from the sphere surface (r >= a).
The time dependent profile is
C(r,t) = Cb - (Cb - Cs)*(a/r)*erfc[(r-a)/(2(Dt)^½]
Please look at "Mathematics of Diffusion" by Crank, a classic tectbook.
BR
Lasse
C(r) = Cb - (Cb - Cs)*(a/r)
where Cs and Cb are the surface and bulk concentrations, respectively, and a is the sphere radius, and r is the distance from the sphere surface (r >= a).
The time dependent profile is
C(r,t) = Cb - (Cb - Cs)*(a/r)*erfc[(r-a)/(2(Dt)^½]
Please look at "Mathematics of Diffusion" by Crank, a classic tectbook.
BR
Lasse
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Posted:
9 years ago
Addition:
What I wrote was without convection. Convection sure changes calculus but the phenomenon as such remains: steady-state is reached rapidly.
Lasse
What I wrote was without convection. Convection sure changes calculus but the phenomenon as such remains: steady-state is reached rapidly.
Lasse