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-   -   Non-condensable Gas (http://www.cfd-online.com/Forums/flow-3d/77246-non-condensable-gas.html)

club68512 June 17, 2010 11:59

Non-condensable Gas
 
hello~every

I have a problem about.... does flow 3D can only have two fluids ?

Can I use Non-condensable Gas(such as air) as the third fluid?

from the User Manual I foundCondensation/Evaporation (Two Fluids with Non-condensable Gas)model,but I don't know how to use it.
I have tried many times but failed...

thanks!

MuxaB June 20, 2010 19:06

You are right, there is a model for the liquid/gas system with the gas consisting of two components: vapor and a non-condensable gas.

There is an sample setup under the folder Examples called Steam-Air, i think, that has the typical input for a water/air/steam system. I think, it uses CGS units.

club68512 June 23, 2010 05:47

Quote:

Originally Posted by MuxaB (Post 263789)
You are right, there is a model for the liquid/gas system with the gas consisting of two components: vapor and a non-condensable gas.

There is an sample setup under the folder Examples called Steam-Air, i think, that has the typical input for a water/air/steam system. I think, it uses CGS units.

THANKS!! I have seen the model for the liquid/gas system .

If I want using Non-condensable Gas(such as air) as the third fluid but don't mix with vapor ,from the initial/fluid region/fraction of non-condensable that I key the value as "1" ,does it means the Non-condensable Gas not mix with vapor??

thanks!

MuxaB June 28, 2010 01:19

Quote:

Originally Posted by club68512 (Post 264160)
THANKS!! I have seen the model for the liquid/gas system .

If I want using Non-condensable Gas(such as air) as the third fluid but don't mix with vapor ,from the initial/fluid region/fraction of non-condensable that I key the value as "1" ,does it means the Non-condensable Gas not mix with vapor??

thanks!

the value of 1 for the NC gas initial volume fraction only defines the initial condition. it does not control the mixing of the two gases. you cannot stop nc gas and vapor from mixing since both are gases and will always be able to mix through diffusion. whether they mix and the rate of mixing ultimately depends on the flow conditions, e.g., pressure and the nc gas diffusion coefficient.

club68512 June 28, 2010 12:06

michael thanks!!

ya! I just want the NC gas initial volume fraction that only defines the initial condition.

I can use something to baffle NC & vapor at initial condition ,the NC & the vapor should not mix,i.e that can be third fluid to use?
I just only want the heat transfer phenomenon by use third fluid(air).
I know the gas in flow3D all follow the IDEAL GAS LAW (P=density*R*T)

I define the NC fraction from the initial/fluid region/fraction of non-condensable that I key the value as "1" ,does anybody know another method to define the NC fraction? coz the fluid region/limiters look likes only the rectangular region to define.

thanks !!!!


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