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Mutiphase - Phase change - small droplets

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Old   October 17, 2016, 21:08
Default Mutiphase - Phase change - small droplets
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Yun Jung
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Dear all,

I am interested in flow field of steam turbine, considering condensation of vapor.

I am using small droplet choice and followings are options I am using.

IAPWS - steam3v and steam3l.

Vapor as continuous fluid
Liquid as droplets(phase change)

For fluid models
Homogeneous model for multiphase
Shear stress transport for turbulence

For fluid specific models
Small droplet temperature heat transfer model for liquid
Total energy heat transfer model for vapor
1 for nucleation bulk tension factor

For fluid pair models
Particle model for interphase transfer
Small droplets and phase change for mass transfer
Small droplets for heat transfer

From CFX theory guide, droplet growth rate is

𝝆𝑳 𝒅𝒓/𝒅𝒕=(k/r)*(1/(1+3.18Kn)*(Td-Tg)/(hg-hp)

nucleation rate J is

𝑱=𝑨𝒆𝒙𝒑[−(∆𝑮∗)/(𝒌𝑻_𝑮 )]

heat transfer Qd is

Qd = (k/r)*(1/(1+3.18Kn)*(Td-Tg)

and Nusselt number is

Nu = 2/(1+3.18*kn)

Those equations are from Gyarmathy(1962), but I want to apply modified model instead of Gyarmathy's.

For example, from Young's model, nucleation rate is same, but droplet growth rate is modified.

So that, Nusselt number becomes following.

Nu = 2/(1+3.78*(1-v)*Kn/Pr)

v=RTs(p)/L[𝜶-0.5-(2-qc)/(2qc)*((𝜸+&#120783/𝟐&#120632*(cp*Ts(p)/L)

L = latent heat

I was trying to use CEL to apply those, but failed.

Is it possible to change equations applied?

I am trying to add 'source term form' to modify equations, but I don't know how to make it.

It this is appropriate way to solve, than please give some advice to apply source term.

I will really be looking forward to you reply.

Thanks.
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Old   October 20, 2016, 02:40
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Roya.TR
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Dear yung,
I see you experienced in multiphases simulations.I would be grateful if you help me.I'm new in multiphase fluid flow
i want to solve a 4 phases flow (gas-oil- water and sand) in a cylinder.
which methods is better for my simulation?
I use eulerian model. is it appropriate?
i chose air as the primary phase but I don't know how define the diameter of liquids.
which method is better for solid with 5-10% volume fraction.
thank you
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Old   October 20, 2016, 03:12
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Yun Jung
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Dear Roya.TR

I think your case is not multi-phase but multicomponent fluid.

I am not sure, but add each component and set volume fraction you want.

I hope it will help you.
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Old   October 20, 2016, 05:17
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Glenn Horrocks
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No, Roya's question is a multiphase model. It has a solid phase (sand) and a gas phase, and the liquid phase is oil and water and in some circumstances they do not mix, which means they can be treated as two liquid phases.

Multicomponent models are for where mixing is at the molecular level, such gas oxygen mixing with nitrogen in air.
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Old   October 20, 2016, 06:14
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Yun Jung
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Dear Ghorrocks

Oh, I understand what you said, and I didn't think about that with mixing concept.

What I wanted to say was Raya's question is not like my phase change problem.

Thanks for fixing my mistake, and can you give any advice with my problem?
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Old   October 20, 2016, 06:33
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Sorry, I have not done anything like your question so cannot help you. Hopefully others on the forum may have some experience and can answer your question.
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Old   October 22, 2016, 01:37
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thanks alot for your response dears
but could you help me about my question?
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Old   October 22, 2016, 04:49
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Quote:
I use eulerian model. is it appropriate?
I have no idea. You have not described any detail of what you are doing.

Quote:
but I don't know how define the diameter of liquids.
If the liquids do not exist as droplets then this does appear to be the correct choice of physical model.

Please describe what you are doing and what states you expect the phases in the flow to be in.
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