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general question about mass fractions/transport

Posted 2014年6月23日 GMT-4 16:54 Chemical Reaction Engineering, Materials, Studies & Solvers Version 4.3b 4 Replies

Aida Rouzmehr
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I have a basic question,
I have two reactors in contact with each other, both starting with the same initial conditions (equal amounts);
compound#1: solvent
Compund#2: A
compound#3: B
while in one of the reactors A is going to B and vice versa in the other reactor. I would assume that when I run the simulation, compounds A & B would diffuse ( the only physics added to the model being diffusion, no convection) and eventually reach a steady state. but when I run the simulation I get a negative mass fraction. how is that even possible?
4 Replies Last Post 2015年9月21日 GMT-4 04:49
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Hello Aida Rouzmehr

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Yuhong Chen
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Posted: 9 years ago 2015年9月19日 GMT-4 09:37
Hi Aida,

I met the same problem as you. Have you figured out it and what's the problem?

yuhong
Hi Aida, I met the same problem as you. Have you figured out it and what's the problem? yuhong
Lasse Murtomäki
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Posted: 9 years ago 2015年9月21日 GMT-4 03:18
Is the reaction homogeneous or heterogeneous? What are the reaction rate equations? Which mass fraction goes negative? Are the reactors connected to each other? Where does diffusion take place?

Perhaps it would be easier to submit your model.

BR
Lasse
Is the reaction homogeneous or heterogeneous? What are the reaction rate equations? Which mass fraction goes negative? Are the reactors connected to each other? Where does diffusion take place? Perhaps it would be easier to submit your model. BR Lasse
Yuhong Chen
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Posted: 9 years ago 2015年9月21日 GMT-4 03:47
Hi Lasse,

Thank u for your valuable time and thinking about my problem.

In fact, I am dealing with the module of transport of concentrated species with homogeneous initial mass fraction of 3 components. There is a mass flux boundary for two of these components without reactions. The other boundary conditions are either no flux or symmetry. When I run the transient simulation to study the concentrations change, it shows correct result at the beginning while it turns out the mass fraction of one component is larger than 1 and the one from mass constrait is negative.

Do you have any ideas about reasons for the errors?

Yuhong
Hi Lasse, Thank u for your valuable time and thinking about my problem. In fact, I am dealing with the module of transport of concentrated species with homogeneous initial mass fraction of 3 components. There is a mass flux boundary for two of these components without reactions. The other boundary conditions are either no flux or symmetry. When I run the transient simulation to study the concentrations change, it shows correct result at the beginning while it turns out the mass fraction of one component is larger than 1 and the one from mass constrait is negative. Do you have any ideas about reasons for the errors? Yuhong
Lasse Murtomäki
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Posted: 9 years ago 2015年9月21日 GMT-4 04:49
Please reply to my questions.
Please reply to my questions.

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