# CFD Analysis of mixing chamber in AHU

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May 22, 2013, 04:49
CFD Analysis of mixing chamber in AHU
#1
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gökhan
Join Date: May 2013
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Hi everybody,

I'm new in CFD. I have questions about boundary condition in fluent. I want to make a cfd analysis to see velocity motion in mixing cell in air handling unit. There are two inlet and two outlet boundary condition. Also there is a mixing damper in the middle. I enter mass flow inlet boundary condition for 1 and two number boundaries and others (3 and 4) are pressure outlet but i couldn't reach good solution . The air which entering from mass flow inlet 1 does'nt mixing with below air .Could you give me a suggestion
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 May 22, 2013, 10:10 #2 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 475 Rep Power: 11 From what I understand, the air entering from inlets has a least path of resistance through pressure outlets. So it will try to move out of the domain from there, instead of entering through the passage joining the two chambers, because there, the pressure will be obviously more than zero. OJ

May 22, 2013, 16:51
#3
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gökhan
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Quote:
 Originally Posted by oj.bulmer From what I understand, the air entering from inlets has a least path of resistance through pressure outlets. So it will try to move out of the domain from there, instead of entering through the passage joining the two chambers, because there, the pressure will be obviously more than zero. OJ
Thank you OJ for your reply . Now i will tell you what i did . I enter 6.2kg/s and +300Pa for mass flow inlet one (1) becasue there is a fan and blowing air toward to left. Secondly I enter +200Pa to pressure outlet one (3). Thirdly i entered -700 Pa to pressure outlet two (2) because there is a fan on the left of boundary condition 4 and suck air from left. Lastly i entered 2kg/s and -600Pa to mass flow inlet two (4). In the result of analysis there is a reversed flow in pressure outlet one ( 2) and air is flowing towards to right and mixing with below air and extract from boundary condition 2.

My target is mixing %80 of first mass flow and %100 second mass flow . %20 of first mass flow must extract from pressure outlet one ( 3)

NOTE: Number in bracket represent the numbers in jpg pictures.
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