# liquid/vapor mass flux boundary conditions

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October 17, 2017, 16:39
liquid/vapor mass flux boundary conditions
#1
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Hi Foamers,

A Simplified geometry for my problem is provided here. I have an evaporator where water comes in from inlet and steam goes out from outlet. I wonder if I can define boundary conditions in the way that mass flux of liquid in the inlet becomes same as mass flux of vapor in the outlet. Can I use groovyBC? How?

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 October 19, 2017, 17:13 #2 Senior Member   Przemek Join Date: Jun 2011 Posts: 245 Rep Power: 14 Hi BarCFD Of course you can, however it should result from void fraction equation rather from boundary condition (but I might be wrong) BarCFD likes this. __________________ best regards pblasiak

 October 23, 2017, 03:38 #3 Member   Andrea Petronio Join Date: Mar 2009 Location: Trieste, Italy Posts: 43 Rep Power: 16 Hi, we addressed this problem while ago. You can find the details in this paper: P. Sosnowski, A. Petronio, V. Armenio, "Numerical model for thin liquid film with evaporation and condensation on solid surfaces in systems with conjugated heat transfer", International Journal of Heat and Mass Transfer 66 (2013) 382–395, in which a laminar case is discussed. Then we analyzed also a turbulent case with LES in: Carlo Cintolesi, Andrea Petronio, Vincenzo Armenio "Large-eddy simulation of thin film evaporation and condensation from a hot plate in enclosure: First order statistics", International Journal of Heat and Mass Transfer 101 (2016) 1123–1137, and in Carlo Cintolesi, Andrea Petronio, Vincenzo Armenio, "Large-eddy simulation of thin film evaporation and condensation from a hot plate in enclosure: Second order statistics", International Journal of Heat and Mass Transfer 115 (2017) 410–423. Hope you can get some usefull hints, ciao BarCFD likes this.

 October 23, 2017, 12:55 #4 New Member   Join Date: Jun 2017 Posts: 11 Rep Power: 7 Thanks a lot Andrea!

 October 24, 2017, 10:37 #5 Senior Member   Charles Join Date: Aug 2016 Location: Vancouver, Canada Posts: 138 Rep Power: 8 You either specify inlet mass flow flux or specify outlet mass flow flux. But you don't specify inlet mass flow flux using outlet mass flow flux. This doesn't make sense that computation could diverge easily.

October 25, 2017, 14:07
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Quote:
 Originally Posted by Marpole You either specify inlet mass flow flux or specify outlet mass flow flux. But you don't specify inlet mass flow flux using outlet mass flow flux. This doesn't make sense that computation could diverge easily.
Thanks Charles,

In fact the idea here is to verify the solvent for boiling in steady state condition. Assume that all vapor exits from boiler (to a condenser ) returns to boiler in the liquid phase.

 October 25, 2017, 16:08 #7 Senior Member   Charles Join Date: Aug 2016 Location: Vancouver, Canada Posts: 138 Rep Power: 8 That's incorrect setting. The flow can be arbitrary which causes your problem as there is a driving force outside of your model. You can measure the flow rate though or, if you have pump, you should know the flow rate from the pump specification.