Nitesh Kumar, 

If your are working with pool boiling case, you can safely assume the following:  

Sub-cooled boiling (I think you call it as initial bubble), if  Tsur = T liquid

and saturated boiling, if  Tsur > T liquid by 10 deg C

If your are working with flow boiling case, then, it is very complicated.  Boiling initiation gets effected by pressure, velocity of flow, inlet sub-cooling and heat flux.  I suggest you to take a sample reading of a similar arrangement, from a reported in literature and use the data suitably.  

Dr.S.Ravindran

I agree with the above comment. You can also check on publications based on boiling in ANSYS Fluent (a lot of papers are available just by googling). Moreover, try this 

http://jingweizhu.weebly.com/blog/cfd-boiling-simulation-project

I don't know whether it suits your problem. But it looks like you can get an idea of vof and stuffs

You have a lot of info available online as Arun mentioned. You may try some of the links below.

http://www4vip.inl.gov/relap5/rius/yellowstone/basu.pdf

https://www.sharcnet.ca/Software/Ansys/17.0/en-us/help/flu_th/flu_th_sec_boiling.html

https://www.youtube.com/watch?v=nTZpn-FQ5e4

https://www.researchgate.net/post/Can_anyone_provide_a_tutorial_describing_boiling_phenomenon_in_Ansys_Fluent

Juan, Thank you very much for the tutorials. I'm working on flow boiling with a initial bubble in 2D channel by using VOF model. But, my solution gets diverged very early. Any help?

Nitesh,

It might be that yours is a very stiff system and small changes in one variable during a step cause the solution to blow up. I would suggest paying attention to the residuals plot to determine which of the variables diverge. Then you can go to "Solution Controls" to change your under-relaxation factors. You can reduce the value of that variable to something like 0.2-0.3 and see if this will help to converge your result. 

You can also go to "Run calculation" and click "Check Case", perhaps you are needing some data to put in before running your case.

Also, it wouldn't hurt if you go back again to your model, materials, and boundary conditions to check if everything is set up correctly.

Good luck

Read the tutorial of Ansys Fluent carefully, however if you want to simulate flow boiling which is happen in heat exchanger or some thing like that it is very complicated because of some fluid flow parameters same as velocity,...

Hi friends, I nee help of you people for flow boiling simulation of water in horizontal tube. I have done successfully this problem for vertical flow condition. In vertical flow boiling simulation I have used wall boiling model under eulerian multiphase flow in fluent. When i'm applying this wall boiling model for horizontal flow, the solution got diverged after some iterations. Can anyone please help me to overcome this problem. If anyone have article/idea related to horizontal flow boiling simulation, kindly share.