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Problem in Condensation

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Old   August 21, 2014, 03:27
Post Problem in Condensation
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Sathya Narayanan
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Greetings everyone,

I'm trying to solve a problem involving Condensation of Saturated steam over a flat plate in ANSYS Fluent 14.0

The problem i faced is: The Steam temperature is reduced upto 285 K without condensing.

The Procedure I followed:

Model: Eulerian Model
Solver: Transient Solver with default options. ( Time step - 0.01 for 1000 iterations )
Geometry: 3D Geometry. I check the condensation on the base plate.
Materials: Phase 1 - Steam; Ph2 - Water.
Mass transfer Mechanism - Evaporation - Condensation mechanism ( Inbuilt ).
Temperature of inlet steam - 374 k.
Base plate temperature - 273 k.
I have changed the values of Standard State enthalpies to the respective values at 373 k and the difference is equal to the Latent heat.

Now after running the simulation, I do not find steam condensing. The following maps were obtained for:

1. Volume fraction of Steam.
2. Heat Flux on the plate.
3. Temperature of stam.

Can you please tell me the problem in the model / mistake in the procedure please.

Should I write a UDF ? Should I use a Steady state solver ?
I'm relatively new to Fluent.
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File Type: jpg Heat flux.jpg (58.4 KB, 47 views)
File Type: jpg FFF.1-16-00109.jpg (55.3 KB, 39 views)
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Old   August 22, 2014, 04:16
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Bill Wang
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Dear satty_00,
I am working on the phase change of water(from liquid to vapor(evaporation) and from vapor to liquid(condensation)) using VOF model in FLUENT. I patched liquid and vapor in different regions at first. Vapor in vapor chamber region and liquid in wick region. Vapor chamber is surrounded by wick. Evaporation and condensation occur at the liquid-wick-vapor interface seperately.
After hundreds of iterations ,the phenomenon is quite strange, in some cases all the liquid turned into vapor while in other cases vapor became into liquid, the others stay unchanged just like the initial circumstances.
I wonder if the FLUENT software is able to simulate phase-change process.
Regards,
Bill
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Old   June 12, 2017, 04:59
Default Condensation in horizontal tube... help please
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Diksha
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Hello Bill, Could you please help me to simulate condensation in a horizontal pipe? My problem is that i don't get it to condense very much. My case is as follows:

>steady, gravity on, CSF on
>Implict VOF: modified HRIC
>primary phase: vapour r134a; secondary: liquid r134a
>SST k-omega
>Inlet: velocity inlet,313.15K
>Outlet: pressure outlet, backflow temp= 313.15K
>Stationary, no-slip wall at 303.15K
> mass transfer: vapour to liquid (inbuilt lee model)

I have a question on the enthalpy.. do i have to set enthalpy of vapour to negative? i have set that of liquid to 0.

Would you please help?

Thank you
Diksha
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Old   October 20, 2018, 18:10
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Quote:
Originally Posted by satty_00 View Post
Greetings everyone,

I'm trying to solve a problem involving Condensation of Saturated steam over a flat plate in ANSYS Fluent 14.0

The problem i faced is: The Steam temperature is reduced upto 285 K without condensing.

The Procedure I followed:

Model: Eulerian Model
Solver: Transient Solver with default options. ( Time step - 0.01 for 1000 iterations )
Geometry: 3D Geometry. I check the condensation on the base plate.
Materials: Phase 1 - Steam; Ph2 - Water.
Mass transfer Mechanism - Evaporation - Condensation mechanism ( Inbuilt ).
Temperature of inlet steam - 374 k.
Base plate temperature - 273 k.
I have changed the values of Standard State enthalpies to the respective values at 373 k and the difference is equal to the Latent heat.

Now after running the simulation, I do not find steam condensing. The following maps were obtained for:

1. Volume fraction of Steam.
2. Heat Flux on the plate.
3. Temperature of stam.

Can you please tell me the problem in the model / mistake in the procedure please.

Should I write a UDF ? Should I use a Steady state solver ?
I'm relatively new to Fluent.
Increase the condensation coefficient in the evaporation and condensation panel or you may write your own DEFINE_MASS_TRANSFER UDF(Fluent's manual has some examples).
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