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Reactive transport of two species

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Hi,
I have two streams of water flow into the same conduit under laminar conditions where they mix by diffusion. Flow is from left to right and compound A enters at the top half, whereas B enters along the bottom half of the left side. Compounds mix and form compound C by a reversible reaction, which is described below. A and B are dissolved, so their diffusion constant is 1E-9 m2/s, but C precipitates as a solid with a diffusion constant of 1E-12 m2/s.

I have defined the forward and reverse rates,concentration and reaction in the variable section.

But I think my product C is not precipitating as a solid. Can anyone guide me as to what I have done wrong?

Attached is my model


3 Replies Last Post 2014年2月11日 GMT-5 10:27

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Posted: 1 decade ago 2014年2月6日 GMT-5 12:15
Hi,

Anyone. Please help. Why is my precipitate which is solid not settling at the bottom of the pipe. I have added gravity to the laminar flow model by modifying the outlet pressure BC and adding volume force.

I have been stuck with this from past 1 month. Any suggestions/pointers will be very much appreciated.

Attached is my model.
Hi, Anyone. Please help. Why is my precipitate which is solid not settling at the bottom of the pipe. I have added gravity to the laminar flow model by modifying the outlet pressure BC and adding volume force. I have been stuck with this from past 1 month. Any suggestions/pointers will be very much appreciated. Attached is my model.


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Posted: 1 decade ago 2014年2月6日 GMT-5 16:27
Romani:

The way you have set up the problem, you will not be able to get solid C to precipitate at the bottom. You are solving a single phase problem where both your reactants (A & B) are in the liquid phase and the product (C) is also in the liquid phase. What you need is a system of equations which solves for the reactants in the liquid phase, just the way you have already described, but the product will have to be converted to a solid depending on its solubility in water or whatever liquid phase you need. I have not solved such a problem before so I cannot give you guidance on how to solve it, but I would start with a 2-phase flow interface with solid + liquid phases. I hope this helps.

Good Luck,
Sri.




Romani: The way you have set up the problem, you will not be able to get solid C to precipitate at the bottom. You are solving a single phase problem where both your reactants (A & B) are in the liquid phase and the product (C) is also in the liquid phase. What you need is a system of equations which solves for the reactants in the liquid phase, just the way you have already described, but the product will have to be converted to a solid depending on its solubility in water or whatever liquid phase you need. I have not solved such a problem before so I cannot give you guidance on how to solve it, but I would start with a 2-phase flow interface with solid + liquid phases. I hope this helps. Good Luck, Sri.

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Posted: 1 decade ago 2014年2月11日 GMT-5 10:27
HI Sri,

Thank you so much for replying..

Romani
HI Sri, Thank you so much for replying.. Romani

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