an error in defination for fluid models
 

Hello everyone,

I am trying to model a simple membrane module with CFX. My current problem is an error when I define two gas materials. The error message said that one constraint component is required for the component fluid models. However, I can not find any positions to fill in the 'fluid models' page for the default domain.

I defined the option for heat transfer to be isothermal at 378K and defined the option for turbulence to be k-Epsilon. None for combustion and none for thermal radiation. Also, the options for two materials(C2H6O & H2O) both is transport equation. That's all what I have set.

I'm a new one in CFX. Hope for help and I would appreciate that very much.

jackeyson

One of your transport equation settings should be "Constrain"

Just as you have said, it was solved.

Thanks a lot.

can you please explain how?

how you did it?

So can anyone share how to solve this issue? In my case, I have Nitrogen/Steam in the system, where the domain initially is filled with Nitrogen and then Nitrogen/Steam mixture enters.

I get an error: "In Analysis 'Flow Analysis 1' - Domain 'Default Domain': One constraint component is required for the component fluid models."

However, if in "Fluid Models", either Nitrogen or Steam option from "Transport Equation" is changed to "Constraint", then I get the following error:
"The object "/FLOW:Flow Analysis 1/DOMAIN:Default Domain/BOUNDARY:inlet/BOUNDARY CONDITIONS" contains the following object: "Steam" whose name is not in the set of those allowed: "Nitrogen"."

So at the end, if one of the components is "Constraint" I lose the possibility to use that component in the system.

Could anyone advice? Thanks.

You should have set it as follows:

- You define a varaible composition mixture with N2 and H2O
- In the domain select the mixture as fluid.
- Then you select to either solve N2 or H2O. So one component has a mass fraction x and the other will be 1-x.
- At the initial conditions, you can set the value for x
- And at the inlet as well.

It it does not work like that, I would start over again. Or define a new variable composition mixture.

You mention steam. What do you mean with steam? Is it just water vapour? Or is it wet steam?