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-   -   model condensation (http://www.cfd-online.com/Forums/flow-3d/69845-model-condensation.html)

club68512 November 6, 2009 09:44

model condensation
 
Hello .

First I must say sorry because my English is poor.

I want model condensation that I wanna tranfer steam(the temperature at 373.12K) to water .

Have anyone the same experience?

I tired many times ,but the density is abnormal

The steam's temperature can be down but the density did not increase!!

the result temperature http://www.wretch.cc/album/show.php?...1549088780&p=0
the initial density http://www.wretch.cc/album/show.php?...1549088781&p=1
the result density http://www.wretch.cc/album/show.php?...1549088782&p=2

If the steam's temperature down transfer to water ,the density(the steam's density is 0.59762) should be increase !!(The water's density is 958.37)

maybe I have wrong with the parameters.
my parameter http://www.wretch.cc/album/show.php?...1549088785&p=5
http://www.wretch.cc/album/show.php?...1549088786&p=6

maybe FLOW 3D can not condense?? transfer steam to water??
Is anybody know ??

please help me... thanks a lot !!

MuxaB November 29, 2009 20:13

Starting with version 9.3 of FLOW-3D, there is an Example problem in the directory $F3D_HOME\Examples\steam_air ($F3D_HOME is the FLOW-3D installation directory) which contains a typical input for a water-air-water vapor mixture, in which water is heated causing it to evaporate into the ullage initially filled with air and vapor. You can use this example to see what needs to be defined for a problem like that.

Michael

MuxaB November 29, 2009 20:20

It looks like you are using vapor properties for water, no? The basic properties of the fluid, such as density, must be those of the water.

Michael

club68512 November 30, 2009 05:07

Quote:

Originally Posted by mike@flow3d.com (Post 238114)
It looks like you are using vapor properties for water, no? The basic properties of the fluid, such as density, must be those of the water.

Michael

Thanks for your reply !!


I use two fluid ,fluid 1=water ,fluid 2=vapor
I want the phase change phenomenon(condensation) (form vapor to water)

I haved run the \Examples\steam_air,but the phenomenon like heated water ,not condensate .

I use vapor properties for vapor not water.

I think I set the flow 3D's model setup have wrong...

MuxaB December 2, 2009 01:38

If you change the heat flux in the steam_air example from positive to negative, it should cause condensation. More importantly, this example contains all the properties and numerical and physical options.

If you are still puzzled, you can send your input to the technical support, if you license allows it.

Michael

club68512 December 3, 2009 00:23

Quote:

Originally Posted by mike@flow3d.com (Post 238422)
If you change the heat flux in the steam_air example from positive to negative, it should cause condensation. More importantly, this example contains all the properties and numerical and physical options.

If you are still puzzled, you can send your input to the technical support, if you license allows it.

Michael

thanks for your reply

I have a big puzzle about the Examples\steam_air's fluid 2 properties
Is the Examples\steam_air fluid 2 steam or air properties?

The fluid 2's density is 0.928 that seems not to be steam
Steam's density should be 0.5976(at 373.12K)
The fluid 2 is steam or air?? can you tell me ?
Because I want the phenomenon that from steam transfer to water .

Sorrry about my poor English...

club68512 December 3, 2009 03:08

Quote:

Originally Posted by mike@flow3d.com (Post 238422)
If you change the heat flux in the steam_air example from positive to negative, it should cause condensation. More importantly, this example contains all the properties and numerical and physical options.

If you are still puzzled, you can send your input to the technical support, if you license allows it.

Michael

sorry~I forgot one thing.

Examples\steam_air ($F3D_HOME is the FLOW-3D installation directory) which contains a typical input for a water-air-water vapor mixture

Do you mean the air mix with vapor is fluid 2??
(The fluid 2's density is 0.928) if you know plaese tell me~ thanks !!


MuxaB December 3, 2009 17:28

fluid #2 represents steam (or vapor). Its density defined in properties does not mean anything because the density is computed from the equation of state using initial pressure and temperature.

MuxaB December 3, 2009 17:31

Quote:

Originally Posted by club68512 (Post 238584)
sorry~I forgot one thing.

Examples\steam_air ($F3D_HOME is the FLOW-3D installation directory) which contains a typical input for a water-air-water vapor mixture

Do you mean the air mix with vapor is fluid 2??
(The fluid 2's density is 0.928) if you know plaese tell me~ thanks !!

Yes the two-component gas mixture of air and vapor is fluid #2. The vapor density is computed from the initial pressure and temperature. The air density is computed from the initial volume fraction defined for the non-condensable gas component.

I it is confusing, I know. Let me know if it clears it.

club68512 December 4, 2009 06:19

Quote:

Originally Posted by mike@flow3d.com (Post 238659)
Yes the two-component gas mixture of air and vapor is fluid #2. The vapor density is computed from the initial pressure and temperature. The air density is computed from the initial volume fraction defined for the non-condensable gas component.

I it is confusing, I know. Let me know if it clears it.


thanks for your reply again!!

I have a problem in the flow 3D in the fluids of model setup.

The phase change item of fluids' setup that only have heated choice
(such as latent of vapor,vapor specific heat..) but don't have condensation(liguids) choice . Therefore I don't know where is the key about the condensation phase change(from vapor to water)...

Is any body know?

MuxaB December 5, 2009 14:29

Quote:

Originally Posted by club68512 (Post 238726)
thanks for your reply again!!

I have a problem in the flow 3D in the fluids of model setup.

The phase change item of fluids' setup that only have heated choice
(such as latent of vapor,vapor specific heat..) but don't have condensation(liguids) choice . Therefore I don't know where is the key about the condensation phase change(from vapor to water)...

Is any body know?

The phase change properties apply to both condensation and evaporation; the direction of the process is not present in the properties in any way. For example, the latent heat is released during condensation and consumed during evaporation.

club68512 December 9, 2009 09:09

Quote:

Originally Posted by mike@flow3d.com (Post 238829)
The phase change properties apply to both condensation and evaporation; the direction of the process is not present in the properties in any way. For example, the latent heat is released during condensation and consumed during evaporation.


thanks for your reply!!!!

But I am still fail .
I just model a simple condenser that full of vapor .
I set the boundaries that only have a heat loss Wall(W=-100) at Zmax the others boundaries are symmetry.

results are density cannot increase to water.....
I try vary times that always fail...


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