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Mass Transfer at a suspended Sphere - Coupling of Convective and Diffusive Transfer

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Mass Transfer at a suspended Sphere - Coupling of Convective and Diffusive Transfer

Hey there,

I'm dealing with a problem concerning mass transfer at a porous solid sphere, suspended in a limited volume of water. I'm struggling to get the problem solved in MathCad. Perhaps has anyone an idea.

The problem is as follows. A solid sphere is suspended in an agitated tank. Mass Transfer is unsteady and described with Fick's 2nd law within the sphere. The flux at the surface is transfered to the bulk liquid by convection. Diffusive and convective flux is coupled at the phase boundary.

I tried to solve it by defining the mass balances in a solve block with pdesolve. Unfortunately there is an error concerning a mismatch of the initial conditions, which I cannot follow up. Actuallly I'm not sure if pdesolve is able to handle the problem. I really do appreciate your input.

Greetinx

Hank

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Re: Mass Transfer at a suspended Sphere - Coupling of Convective and Diffusive Transfer

Try the attached.

Message was edited by: HARVEY HENSLEY added s(t) plot

Re: Mass Transfer at a suspended Sphere - Coupling of Convective and Diffusive Transfer

WoooHaaa. I think you make my day. And now it seems this obvious that I can't believe I haven't seen it.

I will put some more effort in it to make it dimensionless (at the moment it is a little mixed up). If this approach works, s(t) and c(R,t) should be going towards a common value, when the system is in equilibrium (deltac=0).

Thank you very much!

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