# Mutiphase - Phase change - small droplets

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 October 17, 2016, 21:08 Mutiphase - Phase change - small droplets #1 New Member   Yun Jung Join Date: Oct 2016 Posts: 3 Rep Power: 2 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+𝟏/𝟐𝜸*(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.

 October 20, 2016, 02:40 #2 New Member   Roya.TR Join Date: Feb 2014 Posts: 9 Rep Power: 5 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

 October 20, 2016, 03:12 #3 New Member   Yun Jung Join Date: Oct 2016 Posts: 3 Rep Power: 2 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.

 October 20, 2016, 05:17 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,541 Rep Power: 104 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.

 October 20, 2016, 06:14 #5 New Member   Yun Jung Join Date: Oct 2016 Posts: 3 Rep Power: 2 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?

 October 20, 2016, 06:33 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,541 Rep Power: 104 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.

 October 22, 2016, 01:37 #7 New Member   Roya.TR Join Date: Feb 2014 Posts: 9 Rep Power: 5 thanks alot for your response dears but could you help me about my question?

October 22, 2016, 04:49
#8
Super Moderator

Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,541
Rep Power: 104
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.

 Tags small droplets, steam

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