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Condensation of water if humidity > 100%

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Old   November 9, 2010, 17:14
Default Condensation of water if humidity > 100%
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Roman Gobitz-Pfeifer
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Hi,

I'm having a stream of humid air. It's entering an area with almost 100% humidity. While it's flowing trough this area the temperatur will be decreased. Due this it will reach the point where the humidity is >100%. For this case I wanna write a UDF, where the massfraction of water will be decreased, that the humidity will be 100% constant. You'll find the pictures of my problem for the temperatur and the humidity distribution attached.

Here is the UDF I'm planning to write, but I don't know if I can do it like this. I also don't know hoe to determine the massflow of humid air inside one single cell.

I'm looking forward for your suggestions.

cheers wikie

DEFINE_SOURCE(m_source, c, t, dS, eqn)
{
real source=0;

if (C_YI(c,t,'h2o') > massfraction_h2o,sat)
{
source=-massflow_humidair(massfraction_h2o,sat-C_YI(c,t,'h2o')
}

return source;
}
Attached Images
File Type: jpg temperatur distribution.jpg (42.5 KB, 22 views)
File Type: jpg humidity distribution.jpg (41.8 KB, 19 views)
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Old   November 9, 2010, 23:18
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Kitipon
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Hi,WiKie

I think,we should define that droplets are stoped to evaporate or temperature of air are not reduced after humidity reach to 100%(we don't need condensation)but I have never used UDF before now I don't know how to define like that.So,I will study about UDF for 1 or 2 weeks if I get good result I will tell you later.Or if anyone know the good way to solve this please help me.

Anyway, you can cotract me directly in my e-mail (padthai999@hotmail.com) sorry if my English don't clear.

Thank
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Old   November 10, 2010, 12:34
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Roman Gobitz-Pfeifer
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Hi padthai,

this is an another problem I'm working on. I'm trying to simulate a solar driven humidification dehumidification desalination process. On the on hand I'm working on the problem of evaporation (the other thread I've answered your question), on the other hand I'm working on the dehumidification as described in this thread.

cheers wikie
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Old   November 10, 2010, 23:05
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Kitipon
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Hi,Wikie

I have simulated about solar radiation before but I don't know how to define dehumidification.

However,I have seen one paper that is about dehumidifiers(3-D CFD analysis of relative humidity distribution in greenhouse with a fog cooling system and refrigerative dehumidifiers) .I don't know if it will be useful for you but if you want, I will send it to you by e-mail.

Thank
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Old   November 11, 2010, 14:57
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Roman Gobitz-Pfeifer
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HI padthai,

thanks for your help. Please send me this paper to: r-o-m-a-n'at'gmx.de

cheers
wikie
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