Learning Forum

[sachintom1992]

Is there any provision in Ansys fluent to give Incipient Boiling Superheat as input for flow boiling simulations within the Eulerian-Eulerian multiphase flow model?nRegards,nJosephn

[Karthik R]

Hi,nIf you are using the wall boiling models in the Eulerian multiphase models, then the superheat dictates the Nucleation Site Density and is implicitly included in the model through this parameter. Please see Equation 18-488 from Fluent's Theory Guide. This is part of the RPI boiling model.nKarthikn

[sachintom1992]

Sir,n Attached is the screenshot of the Semi-mechanistic wall boiling model within Ansys 2020 R2 Under the boiling model expert options, what does minimum superheat and maximum superheat signifies here? Is it the ONB (Onset of Nucleate boiling) which to be given as input? nRegards,nJosephn n

[Karthik R]

Hello,nThe semi-mechanistic boiling model is based on sub-cooled boiling correlations. Please note that this is compatible with the Mixture Multiphase model. nRegarding Minimum and Maximum Superheats: please see the link below.nI hope this helps.nKarthikn

[sachintom1992]

Sir,n I am doing liquid sodium flow boiling simulation in a narrow annulus channel (Dh = 3.2 mm). From the experiment considered, based on the flow and heat transfer conditions it is given that the inception boiling superheat i.e. ONB superheat is 50K. Where I can add this input data into my simulation?.Regards,nJosephn

[DrAmine]

Sir, I am doing liquid sodium flow boiling simulation in a narrow annulus channel (Dh = 3.2 mm). From the experiment considered, based on the flow and heat transfer conditions it is given that the inception boiling superheat i.e. ONB superheat is 50K. Where I can add this input data into my simulation?Regards,Josephhttps://forum.ansys.com/discussion/comment/107339#Comment_107339

I cannot believe that: I guess they are referring to subcooling temperature and not to wall super heat. Can you check that again?n

[sachintom1992]

Sir,n For liquid sodium boiling under very low flow conditions (say flow velocity 0.2 m/s)), incipient boiling superheat (IBS) will be high. As per the expt. considered w.r.t to the flow and heat transfer, they mentioned IBS as 50 K. So, slug flow regime pattern becomes dominant from inception itself. nCan Chen's semi-mechanistic wall boiling model implemented within the Mixture model in Ansys fluent can capture these physics? nThe minimum superheat value (in the boiling model expert options) can be given as 50K? nRegards,nJosephn