You may want to look interThermalPhaseChangeFoam (VOF) or may be some diffuse interface models if the working fluid is near critical point.

Dear Dr. Navid Zehtabiyan-Rezaie and Dr. Anirudh Singh Rana thank you so much.

Dear Researcher

Please return to the paper

Temperature distribution in a mixture surrounding a growing vapour bubble

Authors

SA Mohammadein, Sh A Gouda

Publication date

2006/3

Journal

Heat and mass transfer

This paper studied the two phases vapour and superheated liquid.

The in your question, the two phases are water and air

then, the model can be adjusted on the basis of your physical problem

Dear Mr.Ijaz Fazil Syed Ahmed Kabir

you can find the answer for your question in the attachment paper, generally you cannot say for the liquid phase water because there are many material in solid, liquid and vapoure and that depending on the nature of material beside the conditions.

Article Thermal Efficiency for Passive Solar Chimny With and Without...

with my respect

Ali Dawood Salman Dear Sir my specific problem is I need to model a heat exchanger in which liquid air (-160 deg C) and water exchanges energy. Since liquid air is admitted it has to lose its energy and convert to air (gaseous phase). So two fluids involved air and water in which air has to undergo phase change from cryogenic state to normal state.

Hello Ijaz Fazil Syed Ahmed Kabir ,

you might use the chtMultiRegionTwoPhaseEulerFoam. Heat conduction through the solid is calculated as well as multiple fluid regions with different thermophysical properties, separated by your solid for example and liquid-vapour phase change is included by an Eulerian approach.

Keep in mind, that OpenFOAM of course uses Kelvin for temperature and not °C, so no negative Temperatures should be applied.

Maybe that helps.

Dear David Sonntag thank you so much. I have you used chtMultiregion for heatexchange between two fluids and solid. I saw the description of this foam 'Transient solver for buoyant, turbulent two phase fluid flow andsolid heat conduction with conjugate heat transfer between solid and fluid regions.' I just need to confirm, Can I use another fluid (water) in addition to the phase changing fluid like conventional chtmultiregion.

Yes you can, if those different fluids are separated. Just add another fluid region to your case.Then you can define individual thermophysicalProperties.

Let's say you have your heat exchanger which is set as a solid region, then you can define water as one fluid region on the outside of the HX and and Air as another flui region on the inside of the HX. The two fluids will be interacting with eachother only thermally.

Also take care about cell size inside the solid and near the wall. There the cells need to be approximately of same height normal to the interface to get good results.

Dear David Sonntag Thank you so much.

What if there is only one substance existing in a vertical tube( water and vapor for example) and I need to consider the natural convection as well? So which solver do you recommend?

Thanks.

Hi,

I guess you could chose one of the two fluid inter solvers. They are based on Volume of Fluid and easy to apply. But you should really take care about cell resolution for good results of course. To take account for natural convection just apply boussinesq or polynomial thermophysicalProps. For polynomials you need to fit function coefficients according to your const. Pressure and temperature range. Unfortunately it can happen, that property calculation is not that precise.

On the other hand it is possible to chose euler solvers instead of inter solvers of course. But in my opinion you need really deep knowledge about all those empirical coefficients.

Hope that helps.

Regards David