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-   -   modeling of coupled problem (http://www.cfd-online.com/Forums/fluent/29774-modeling-coupled-problem.html)

Godfrey May 17, 2002 17:25

modeling of coupled problem
 
Dear all,

I am going to model a catalytic combustion process, which is used to burn off the trace amount of fugitive ethane. The case description are as below: (1) I have to use a hot gases from exsting burners , to raise the temp of my process, I planned to use a configuration like a double pipe heat exchanger, but the gases to be burnt will be entering from the side

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| | burnt gases out

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| | | < - gases to be burnt

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hot gases

My problem is how can I couple the two flow in order to run the calc. , and how could I specify the heat transfer from the hot gases to the cold stream.

I expect your suggestion/experience/thought to direct my modeling of this combustion process. I appreciate your time and expertise.

Godfrey


chiseung May 18, 2002 09:30

Re: modeling of coupled problem
 
I suggest this method.

(1) Set the momentum and energy boundary conditions and turn off the "energy" equation in "solve->control".

(2) Solve each flow field separately in a same geometry. An approach to solve this problem is to set one flow field as a solid part and solve the other field. Then export solved flow field data by the function "interpolate" in a Fluent solver. Thus, you can solve the other flow filed in a same manner.(change the solid type continuum and fluid type continuum)

(3) Couple two flow field data in a same geometry and turn off the "flow" equation and turn on the "energy" equation in "solve->control". Then solve energy equation only.

P.S. Above method is valid when there is no natural convection and flow field variables(velocity components) are not governed by temperature.

Godfrey May 21, 2002 13:24

Re: modeling of coupled problem
 
In this case there is natural convection on outer fluid side as well as the temperature is very influential in flow field..

Godfrey

chiseung May 21, 2002 22:04

Re: modeling of coupled problem
 
Well, how about using "Profile file" in solver? Boundary condition at interface between two regions could be set after solving hot fluid region. Thus you can, I believe, solve the natural convection problem caused by hot fluid region which is spacially separated with cold fluid region.

Godfrey May 22, 2002 15:52

Re: modeling of coupled problem
 
Ok I will try this..

but could I use the inner wall as inteface where I can define my boundary condition or I should defined the new interface boundary condition..?? thanx for help


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