# Condensation of water if humidity > 100%

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November 9, 2010, 17:14
Condensation of water if humidity > 100%
#1
Member

Roman Gobitz-Pfeifer
Join Date: Dec 2009
Location: Stuttgart
Posts: 80
Rep Power: 9
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
 temperatur distribution.jpg (42.5 KB, 26 views) humidity distribution.jpg (41.8 KB, 23 views)

 November 9, 2010, 23:18 #2 New Member   Kitipon Join Date: Oct 2010 Posts: 16 Rep Power: 8 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

 November 10, 2010, 12:34 #3 Member   Roman Gobitz-Pfeifer Join Date: Dec 2009 Location: Stuttgart Posts: 80 Rep Power: 9 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

 November 10, 2010, 23:05 #4 New Member   Kitipon Join Date: Oct 2010 Posts: 16 Rep Power: 8 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

 November 11, 2010, 14:57 #5 Member   Roman Gobitz-Pfeifer Join Date: Dec 2009 Location: Stuttgart Posts: 80 Rep Power: 9 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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