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-   -   multiphase about the electrolysis ~ ple help me (https://www.cfd-online.com/Forums/fluent/40094-multiphase-about-electrolysis-ple-help-me.html)

 Luke March 12, 2006 13:53

multiphase about the electrolysis ~ ple help me

hellow everybody:

My name is Luke. I am trying to simulate the chemical reation which is about the multiphase flow (two phase). I consider the liquid-water in a electrolyzer and there are two electrodes in it.

I want to electrolysis the liquid-water and produce the H2 at the surface of cathode and the O2 at the surface of anode. Beside, the mass of the H2O(consumpted), H2(generated) and O2(generated)must to be shown or calculated in my problem.

The simple chemical reaction is below.

H2O(liquid)---->H2(gas) + O2(gas)

This problem is involved with the multiphase and the species transport. Which multiphase model should I choose? And how can I see the phenomenon of the species transport? And how can I calculate the amount of the H2 or O2 which is generated by the chemical reation?

 Luke March 14, 2006 05:06

Re: multiphase about the electrolysis ~ ple help m

pls help me. Thank you~

 kharicha March 14, 2006 09:18

Re: multiphase about the electrolysis ~ ple help m

Question: do you expect a lot of small bubbles (100-1000) created in the same time or a limited number of big bubbles growing slowly ?

In the first case : use mixture or Euler-Euler model. In the second case use VOF....

your questions are welcome.

 grzesiek March 15, 2006 13:27

Re: multiphase about the electrolysis ~ ple help m

quastion to kharicha What if we have a free surface (like somethinf filled to 1/2 of volume)?

 kharicha March 16, 2006 04:47

Re: multiphase about the electrolysis ~ ple help m

This is a problem!

The only method (in FLUENT)that can deal with a free surface is the VOF method....but this method is not able to model a mixture area.

Presently, I am dealing with a phenomena which is similar to raining over a free surface which I want to exactly track.

For the mixture (rain+air) I use a transport equation which compute the proportion of the rain phase over the gas phase. When the concentration reach the interface i convert the concentration into mass of liquid. So the level of interface is increasing while the concentration is absorbed.

This is valid only if the concentration of rain phase is much smaller than the gas phase (few percent). And the droplet size should be much smaller than your grid size.

But if you are not interested by tracking exactly the interface, you can use the mixture or the Euler-Euler approach, which nevertheless are not so bad for interfaces which are not subject to special phenomena (surface tension, magnetohydrodynamic....etc

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