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Coupling for heat source term from reaction engineering or chds module

Posted Feb 8, 2011, 8:06 a.m. EST Fluid & Heat, Heat Transfer & Phase Change, Chemical Reaction Engineering, Geometry Version 4.1 7 Replies

Shalaka Shah
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Dear Experts

I am a student at IIT madras

I am strugling from last one month to get an heat source term in HT module.
My problem is, I have a catalytic reaction taking place in micro reactor at wall. Its an highily exhothermic reaction. Due to exhothermic heat, temperature in reactor will increase and in turn increases rate of reaction. And hence it is a 2 way coupled problem where mass and heat transfer equation need to be solved simultaneously.

The model which i have created is as follows.
1 mod1: only reaction enggineering
2.mod2: mod1 is syncronized with multiphysics having Laminar flow, Heat transfer in solids and fluids, Diluted species module

Please help me out to get correct effect of heat liberated in reactor due to moles reacted at surface. And i have surface reaction, not an volumetric reaction. I want an coupling in such way that boundry heat source should come as {delt_Hr [J/mol] *rate of product [mol/m^2/s]}.

I have attched the file. IN that in HT module i have tried to give manually boundry flux formula by multiplying delt Hr with Rsurf rateof product from mod1. But solution is not converging.

Regards
Shalaka

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7 Replies Last Post Mar 31, 2011, 11:37 a.m. EDT
Mayur
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Posted: 1 decade ago Mar 9, 2011, 2:28 a.m. EST
Hi
You don't need to use reaction engineering physics, just define all your rate expression as variables and just use diluted chemical species physics along with flow. I have solved more complicated kinetic models than this case without using reaction engineering physics.
MM
Hi You don't need to use reaction engineering physics, just define all your rate expression as variables and just use diluted chemical species physics along with flow. I have solved more complicated kinetic models than this case without using reaction engineering physics. MM
Shalaka Shah
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Posted: 1 decade ago Mar 9, 2011, 2:39 a.m. EST
Thank you for your reply. But i have exhothermic reaction, how to take into account for heat of reaction? heat transfer between wall and flow is very critical aspect of the simulation. Because in CHDS module i can only specify my rate expression. But all my rate constants will change with temperature and i want an coupling between Temperature and reaction, As i am cooling my reactor with convective flux because of exhothermic heat of reaction

Shalaka Shah
Thank you for your reply. But i have exhothermic reaction, how to take into account for heat of reaction? heat transfer between wall and flow is very critical aspect of the simulation. Because in CHDS module i can only specify my rate expression. But all my rate constants will change with temperature and i want an coupling between Temperature and reaction, As i am cooling my reactor with convective flux because of exhothermic heat of reaction Shalaka Shah
Shalaka Shah
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Posted: 1 decade ago Mar 9, 2011, 2:39 a.m. EST
Thank you for your reply. But i have exhothermic reaction, how to take into account for heat of reaction? heat transfer between wall and flow is very critical aspect of the simulation. Because in CHDS module i can only specify my rate expression. But all my rate constants will change with temperature and i want an coupling between Temperature and reaction, As i am cooling my reactor with convective flux because of exhothermic heat of reaction

Shalaka Shah
Thank you for your reply. But i have exhothermic reaction, how to take into account for heat of reaction? heat transfer between wall and flow is very critical aspect of the simulation. Because in CHDS module i can only specify my rate expression. But all my rate constants will change with temperature and i want an coupling between Temperature and reaction, As i am cooling my reactor with convective flux because of exhothermic heat of reaction Shalaka Shah
Mayur
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Posted: 1 decade ago Mar 9, 2011, 10:18 a.m. EST
Hi,
under heat/energy transfer physics you should find the option for heat source, you can define heat source as deltaH*R, where R is the reaction and delta H is the enthalpy of the reaction which may or may not be depend upon temperature. You should define all the rate constants in terms of variable T (temp) of heat transfer physics, which allow you to vary all the rate constant as T varies. I have attached one model, probably you have already gone through it but worth while to look at it again, which describe how to define heat source in energy transfer physics.
Mayur
Hi, under heat/energy transfer physics you should find the option for heat source, you can define heat source as deltaH*R, where R is the reaction and delta H is the enthalpy of the reaction which may or may not be depend upon temperature. You should define all the rate constants in terms of variable T (temp) of heat transfer physics, which allow you to vary all the rate constant as T varies. I have attached one model, probably you have already gone through it but worth while to look at it again, which describe how to define heat source in energy transfer physics. Mayur

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Mayur
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Posted: 1 decade ago Mar 10, 2011, 10:10 a.m. EST
In your model you are defining heat source on the boundary and all the reactions in subdomain..I think you need to define all species reactions on boundary as well by considering flux boundary condition in chds.
In your model you are defining heat source on the boundary and all the reactions in subdomain..I think you need to define all species reactions on boundary as well by considering flux boundary condition in chds.
Qasim Ali Chaudhry
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Posted: 1 decade ago Mar 31, 2011, 9:34 a.m. EDT
Dear Mayur,

Thanks for posting valuable discussion. Is there any model available which defines the species reactions on boundary as well by considering flux boundary condition.

Thanks

Best Regards

Qasim
Dear Mayur, Thanks for posting valuable discussion. Is there any model available which defines the species reactions on boundary as well by considering flux boundary condition. Thanks Best Regards Qasim
Mayur
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Posted: 1 decade ago Mar 31, 2011, 11:37 a.m. EDT
just define flux boundary condition where you want reactions to occure and insert reaction expressions for each chemical species and make sure you have the same unit of your reaction expressions as flux..i,e mol/m^2/s)..
cheers
Mayur.
just define flux boundary condition where you want reactions to occure and insert reaction expressions for each chemical species and make sure you have the same unit of your reaction expressions as flux..i,e mol/m^2/s).. cheers Mayur.

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