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 sega March 15, 2010 15:01

DPM - Solid reaction

Hello world.

I'm trying to simulate a solid reaction inside an ash particle.
Therefore I am using the Discrete Phase Model (DPM).
Nothing special so far, DPM works fine.

Let's consider this:
I want to apply the DPM on a converged simulation of a power plant.
So I am using the DPM without interaction with the continuous phase.
All variables inside the domain are solved, therefore I have the whole zoo of species concentrations at hand.

The most important species to me is oxygen. Why?
Because I want to simulate this reaction:

+ 0.5

Fe and FeO are part of the mineral ash inside the particle.
So I am tempted to define the volume fraction of my particle with two User Defined Scalar:

Code:

P_USER_REAL(p,0) = 1.0 P_USER_REAL(p,1) = 0.0
These two values correspond to 100% Fe and 0% FeO at the beginning of the caluclation.

Typical laws for the propagation of such species are

where and corresponds to the volume fraction of the species and time. is some coefficient.

Now there is my problem:
The species volume fraction inside the particle are 1 for and 0 for .
The application of these numbers to the above law will lead to zero reaction (because 1 - X = 1 - 1 = 0). This can't be right.

The obvious reason? Oxygen!
I think I need to include the oxygen into my considerations.
The reaction will only take place in an oxygen environment.
Remember: The oxygen is part of the allready calculated solution inside the domain.

What I am not sure about is the connection between my definition on the particle itself (the User Defined Scalars) and the oxygen concentration in the domain.

The volume -concentration of the system containing my particle and oxygen will be less than 1 ...

I'm not sure how to approach this.
How can I tell if stoichiometric conditions apply?
(How do I identify the conditions at all?!)
What happens if there is less/more oxygen than needed?

Feel free to answer. Any help is appreciated.

 hane April 12, 2014 14:02

help

thats an intersting simulation
can you post ur udf codes here
i want to have a look at them

 gearboy April 13, 2014 21:48

Quote:
 Originally Posted by sega (Post 250123) Hello world. I'm trying to simulate a solid reaction inside an ash particle. Therefore I am using the Discrete Phase Model (DPM). Nothing special so far, DPM works fine. Let's consider this: I want to apply the DPM on a converged simulation of a power plant. So I am using the DPM without interaction with the continuous phase. All variables inside the domain are solved, therefore I have the whole zoo of species concentrations at hand. The most important species to me is oxygen. Why? Because I want to simulate this reaction: + 0.5 Fe and FeO are part of the mineral ash inside the particle. So I am tempted to define the volume fraction of my particle with two User Defined Scalar: Code: P_USER_REAL(p,0) = 1.0 P_USER_REAL(p,1) = 0.0 These two values correspond to 100% Fe and 0% FeO at the beginning of the caluclation. Typical laws for the propagation of such species are where and corresponds to the volume fraction of the species and time. is some coefficient. Now there is my problem: The species volume fraction inside the particle are 1 for and 0 for . The application of these numbers to the above law will lead to zero reaction (because 1 - X = 1 - 1 = 0). This can't be right. The obvious reason? Oxygen! I think I need to include the oxygen into my considerations. The reaction will only take place in an oxygen environment. Remember: The oxygen is part of the allready calculated solution inside the domain. What I am not sure about is the connection between my definition on the particle itself (the User Defined Scalars) and the oxygen concentration in the domain. The volume -concentration of the system containing my particle and oxygen will be less than 1 ... I'm not sure how to approach this. How can I tell if stoichiometric conditions apply? (How do I identify the conditions at all?!) What happens if there is less/more oxygen than needed? Hope I made myself clear. Feel free to answer. Any help is appreciated.
Your fomular is similar to the first-order of volatile release in coal combustion. The X doesn't mean the fraction of Fe left in the solid, but means that the Fe yield. On the contrary, (1-X) means Fe left in the solid. Therefore, at the beginning, the 1-X=1, which will let you get largest reaction rate. When the Fe burns up, 1-X=0, the reaction rate will be zero.

 gearboy April 13, 2014 21:58

Quote:
 Originally Posted by sega (Post 250123) Hello world. I'm trying to simulate a solid reaction inside an ash particle. Therefore I am using the Discrete Phase Model (DPM). Nothing special so far, DPM works fine. Let's consider this: I want to apply the DPM on a converged simulation of a power plant. So I am using the DPM without interaction with the continuous phase. All variables inside the domain are solved, therefore I have the whole zoo of species concentrations at hand. The most important species to me is oxygen. Why? Because I want to simulate this reaction: + 0.5 Fe and FeO are part of the mineral ash inside the particle. So I am tempted to define the volume fraction of my particle with two User Defined Scalar: Code: P_USER_REAL(p,0) = 1.0 P_USER_REAL(p,1) = 0.0 These two values correspond to 100% Fe and 0% FeO at the beginning of the caluclation. Typical laws for the propagation of such species are where and corresponds to the volume fraction of the species and time. is some coefficient. Now there is my problem: The species volume fraction inside the particle are 1 for and 0 for . The application of these numbers to the above law will lead to zero reaction (because 1 - X = 1 - 1 = 0). This can't be right. The obvious reason? Oxygen! I think I need to include the oxygen into my considerations. The reaction will only take place in an oxygen environment. Remember: The oxygen is part of the allready calculated solution inside the domain. What I am not sure about is the connection between my definition on the particle itself (the User Defined Scalars) and the oxygen concentration in the domain. The volume -concentration of the system containing my particle and oxygen will be less than 1 ... I'm not sure how to approach this. How can I tell if stoichiometric conditions apply? (How do I identify the conditions at all?!) What happens if there is less/more oxygen than needed? Hope I made myself clear. Feel free to answer. Any help is appreciated.
In my opinion, you'd better correlate the coefficient K with the O2 concentration so as to include the O2 effect.

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