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Convective mass transfer from a sphere

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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.

2 Replies Last Post 17 nov 2015, 01:42 GMT-5

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Posted: 9 years ago 17 nov 2015, 01:35 GMT-5
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
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

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Posted: 9 years ago 17 nov 2015, 01:42 GMT-5
Addition:

What I wrote was without convection. Convection sure changes calculus but the phenomenon as such remains: steady-state is reached rapidly.

Lasse
Addition: What I wrote was without convection. Convection sure changes calculus but the phenomenon as such remains: steady-state is reached rapidly. Lasse

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