CFX simulate boiling&condensation simultaneously?
 

Can CFX simulate boiling and condensation simultaneously? For example, a closed box, contains about half box of water at first, then heats the bottom and cool the top. Water will get boiling, and water stream will condense at the top wall. Can CFX simulate this complicated phenomena? If so, please send me some related information.

Best Regards,

whiz

Re: can somebody help me?
 

none

Re: CFX simulate boiling&condensation simultaneous
 

Yes. Try the inhomogeneous multiphase + thermal phase change. It can be done but you will need CPU time, mesh resolution and patience.

Re: CFX simulate boiling&condensation simultaneous
 

Dear Neale, I found that if simulate boiling, the water is treated as continuous fluid, and the water vapour as dispersed fluid. But to simulate condensation, the water is treated as dispersed fluid, and the water vapour as continuous fluid. Am I right?

If boiling and condensation can be calculated simultaneously, how to set the heat transfer model between the two fluid (water and water vapour)?

Are the all continous fluid? How to set the it?

Bow

with best Regards,

whiz

Re: CFX simulate boiling&condensation simultaneous
 

Try creating two domains and modelling them seperately. The lower domain can be a water continuoul domain and the upper as a vapour continuous domain.

Try this

Re: CFX simulate boiling&condensation simultaneous
 

Welcome to the world of multiphase modelling. What you are doing is not easy. You will always need to run with:

- inhomogenous heat transfer - thermal phase change model - two resistance heat transfer option.

If your flow regime does not fall into the classical continuous-disperse category then you may not be able to use any of the continuous-disperse heat transfer relationships (eg: Ranz Marshall).

You will have to play around with one of the other options (eg two heat transfer coefficients, two Nusselt numbers, etc..) until you get something that looks sensible. It will depend on your flow regime: small bubbles, large bubbles, bubbles, slugging, etc...

Neale.

neale thank you......