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-   -   Modeling Condensation in water vapour-air mixture (http://www.cfd-online.com/Forums/main/4495-modeling-condensation-water-vapour-air-mixture.html)

Amol March 5, 2002 09:10

Modeling Condensation in water vapour-air mixture
 
Can any one throw some light on "Modeling Condensation in vapour-air mixture".. to be precise... Is their any commercial code that will solve these kind of problems ???

I would appreciate your responses

Thanks

Amol

Peter Rozovski March 5, 2002 17:03

Re: Modeling Condensation in water vapour-air mixt
 
I can reccomend this book about numerical simulation of condensation

Nonequilibrium Condensation in High Speed Gas Flows by Yu A. Ryzhov, U.G. Pirumov, V.N. Gorbunov http://www.amazon.com/exec/obidos/AS...159262-3232920

If you have some commercial CFD product like FLUENT or CFD-ACE you can add condensation model by yourself by UDF - the simplest model consists from 4 ODE along streamline. Condensation of water wapor in mixture with air is pretty well been studied, but the main question - what you are interesting in ? Temperature levels or location of Wilson's line can be predicted by simple model, with droplets size distribution function situation is worse.

Herve March 7, 2002 05:15

Re: Modeling Condensation in water vapour-air mixt
 
Amol,

If I'm not mistaken this has been looked at by some CFX people. Get in touch with their indian office for info: Mr Hari Doss AEA Technology Engineering Software 16 Jayamahal Main Road, Bangalore 560-046 India

Tel:+91 (80) 226 7272 Fax: +91 (80) 225 1133 Email: haridoss@vsnl.com


Jing March 7, 2002 10:15

Re: Modeling Condensation in water vapour-air mixt
 
In StarCD, I have simulated the condensation by programming the nucleation and droplet growth model. The Young's nucleation model and Gyarmathy's droplet growth model are all very popular in the region of condensation. You can try them.

Amol March 8, 2002 09:42

Re: Modeling Condensation in water vapour-air mixt
 
Thanks Peter

I would really appreciate if you can give some more insight about how I should model this through udf.. and you guess is correct .. I want to know "droplets size distribution"

Thanks again

waiting for you response.

Amol

Amol March 8, 2002 09:47

Re: Modeling Condensation in water vapour-air mixt
 
Thanks Herve !

Amol March 8, 2002 09:52

Re: Modeling Condensation in water vapour-air mixt
 
Jing

I would appreciate if you can give some more info about it,,

Thanks in advance..

Anant

Peter Rozovski March 8, 2002 14:39

Re: Modeling Condensation in water vapour-air mixt
 
The simple model of condensation is based on dividing the whole process into two separate steps - nucleation and droplet growth. It is dishonest - but in some situations it works. After it the nucleation rate is calculated by Frenkel-Zeldovich expression, and droplet growth - by some other expression (there are a lot of variants). In this case one has no need to calculate cluster size distribution function itself but can calculate only first 4 moments for it. So one has system from 4 ODE. This was usual approach for a long time and a lot of simulations of condensation of water vapors in turbines were done by such method, which was described in many books, but I prefer the one which I reccomended to you. The good agreement with experimental data is achived by fitting parameters. For some substances such approach works good, for other - not (Lothe-Pound paradox, etc.). For water it works. I think, 99.999% of all calculations of condensation were done for condensation of water vapors. But it also depends from two other main factors : average cooling rate between saturation point and Wilson's point and mass fraction of monomers. If cooling rate (the temperature gradient) is less than 1000-10000 K/sec - Frenkel's formula works. There a lot of details here. But the great disadvantage of such approach is that you don't have cluster size distribution function. If you really(!) need it - there are two approaches. If you are working with small clusters - honestly solve the system of ODE for nucleation process (I was using such approach to simulate metal cluster formation and growth for metal clusters beam generators). If you are working with large droplets - solve the system of equations for different fractions of droplets. It is hard to make more detail advise without knowledge of your problem.

About UDF. It again depends from your problem, but in many cases you can put selected model into your own code and call this code from commercial solver after each time step to recalculate heat source (result of condensation) and mixture molecular weight and enthalpy (function of P,T and cluster size distribution function). In CFD-ACE such approach can be realized. I have no hand-on-experience with FLUENT, but it is clear that situation is the same. If you have more questions - you can use my e-mail.


Jing March 11, 2002 05:55

Re: Modeling Condensation in water vapour-air mixt
 
Hi, Amol

Peter has described the nucleation and droplet growth process in detail. I just add something.

For the homogeneous condesation, the classical nucleation theory is good enough. You can get the droplet size and number distribution at the nucleation line with the nucleation equation. Please check the following paper:

Young, J. B., 1992. Two dimensional, nonequilibrium, wet-steam calculation for nozzles and turbine cascade. J. of Turbomachinery, Vol. 114, 569-579.

In the following flow passage, the droplet growth process could be simulated by the Gyarmathy's equation. Please check:

Gyarmathy, G. et.al.1973. Spontaneous condenstion of steam at high pressure : First experimental results. Instn Mech. Engrs. Wet Steam 4. Paper C66/73 Conference, Univ. of Warwick.

Hopefully they are helpful!

Jing

Amol March 13, 2002 05:14

Re: Modeling Condensation in water vapour-air mixt
 
Thanks Peter

I will definately get back to you on this.


Amol March 13, 2002 05:16

Re: Modeling Condensation in water vapour-air mixt
 
Jing

Thanks a lot for those references.

mactech001 January 28, 2010 10:09

would anyone have any tutorial/procedure to help me kick start on modeling heat transfer using spray liquid please?

salam August 12, 2010 05:23

wet steam model
 
hello every one.
I have a high pressure real gas that contains water vapor.and in my model condensation of water and growth of the droplet size is occurred.can I use the wet steam model and if yes can i use the srk eos as the udf in my work?
thanks a lot

zino April 25, 2011 10:20

modeling dust particles in air flowing through a pipe FLUENT
 
hey!
Can any one tell me how can i model multiphase flow silicon/any metal particles flowing through a pipe in Fluents by using eluer-euler approach?
say volume fraction of metal is 0.2

Spring.s April 10, 2012 00:28

Quote:

Originally Posted by salam (Post 271265)
hello every one.
I have a high pressure real gas that contains water vapor.and in my model condensation of water and growth of the droplet size is occurred.can I use the wet steam model and if yes can i use the srk eos as the udf in my work?
thanks a lot

Hi
Can you use the wet steam model for high pressure steam flow?
I can't achieve to convergence in solution for high pressure flow. Can you help me?
Thanks


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