Dear Somnath, here is the answer that I had promised. Your question shows up the trend these days to rush to commercial programs like ANSYS Fluent etc. You will see from my answer that we have NO need to solve the N-S equations at all here.

I am hoping to get the opinion of Oguz Emrah Turgut on my answer.

Just out of curiosity: Is this part of a masters thesis, an industrial consultancy work or any other?

Like I said earlier, if it is a shell and tube heat exchanger you are considering, your calculation will be infinitely more complicated. Better to leave it to a licensed software like that of HTRI.

tell me about ur geometry is in 2D or 3D. pls search on you tube i.e. numerical simulation of  pool boiling phenomenon, related to this i also work on evaporation & condensation model but it is for 2D model for pool boiling. Where u get the condition used for the problem definition.

https://www.youtube.com/watch?v=vzCXutLLiE4

see this video

at left bottom of video u will find the condition used for the problem.

To my best knowledge, it is not possible to model two phase flow boiling phenomena in any finite element based computational flow dynamic solver since heat and mass transfer mechanism takes place in this process does not work under the principles of Newtonian flow dynamics. The essence of heat and mass transfer dynamic is a bit of randomized and   under the effect of heat flux, tube wall temperature, working fluid temperature, etc. I have used finite difference method in modelling evaporator (or condenser) with the available two phase flow boiling correlations. It does not guarantee the exact solutions, but so far, it gives semi-exact results. Therefore, rather than comsaol or fluent, I recommend you to use the finite difference model. 

Sir Oguz Emrah Turgut,

It is very much possible to model boiling and condensation in Fluent which is based on finite difference & finite volume method. I have modeled those phenomenon but getting different answers by each Multi phase models like VOF, Eulerian & Mixture which are available in ANSYS FLUENT package.

Any further inputs on this topic would be very much appreciated,

Thanks!

Mr. Somnath Rangrej, may be the file below is benefit 

Dear Somnath,

The answer to your question is too involved and I would not have ventured to answer it, except that I was rather touched by your personal message requesting help.

If you are willing to write your own numerical algorithm rather than use a commercially available program, you may use the procedure that I am writing for you now. I will post it as an attachment when finished. It can be done using just an Excel program. As Oguz says, the real complexity here is the uncertainty associated with the boiling correlations and condensing correlations. Your result will only be indicative and unless you perform a good experiment to benchmark your calculation method, you cannot be certain that you will get reasonable answers. You certainly should not use your result for design unless verified by experiment.

I also agree with Oguz about using finite volume etc. Using VOF, Eulerian & Mixture etc. which are available in ANSYS FLUENT package is quite meaningless as you will soon see in my post. That is the reason why you are getting different answers.

Fortunately, in your scheme, it is co-flow in a double pipe apparatus, which means that it is an explicit scheme of solution and you can use a marching technique. I presume that your intention is to find the length required to achieve complete evaporation as well complete condensation. If you were asking about a shell and tube evaporator-condenser, I would have directed you to HTRI's design package.

Kindly await my next post with the attachment. In the meantime, you can avoid getting confused by some unhelpful answers that have already been posted, showing that the correspondents have no understanding of your question whatever!

Thanks Vijay Raghavan Sir,

for your detailed description, I will surely wait for your reply!

Dear Somnath, here is the answer that I had promised. Your question shows up the trend these days to rush to commercial programs like ANSYS Fluent etc. You will see from my answer that we have NO need to solve the N-S equations at all here.

I am hoping to get the opinion of Oguz Emrah Turgut on my answer.

Just out of curiosity: Is this part of a masters thesis, an industrial consultancy work or any other?

Like I said earlier, if it is a shell and tube heat exchanger you are considering, your calculation will be infinitely more complicated. Better to leave it to a licensed software like that of HTRI.

This is a part of my Masters thesis Sir, Thanks all for your time and guidance. Anymore suggestions if you have please do post here,

Thanks!

Dear Somatha

there are some tutorials in the literature in evaporating and condensation using FLUENT software, I will try to attach one of these tutorials, I also attach a good text book in evaporation and condensation in heat transfer, I hope this will be helpful.

Regards

Saleh Etaig