# a basic air ventilating(exhaust) problem

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 December 5, 2014, 15:32 a basic air ventilating(exhaust) problem #1 New Member   Join Date: Feb 2014 Posts: 1 Rep Power: 0 Hello dear cfd online folks I am a mechanical engineer student who should finish his project very soon. One part of my project is analyze the technical drawing which is related to project and get the velocity analysis. It seems that i am lack of knowledge when the case is 3d geometry. So i made some simplification about geometry Basically i design a unit volume and put two outlet which should suck 5m/s of air from the unit volume and throw it to atmosphere from roof. Thats all i need. So i put them upper side of my unit volume(that is also represent my roof boundary) and start solver but i couldnt get a reasonable solution at all. I both try outlet type and fan type for my air hole and they do not help. I am open for any suggestion. I use "phoenics". Best regards.

 December 9, 2014, 09:40 #2 Member   Roman Gobitz-Pfeifer Join Date: Dec 2009 Location: Stuttgart Posts: 83 Rep Power: 13 hello incememed, do you want to create a vacuum? Two outlets and no inlet won't work. You need at least one additional inlet or opening in your room as well. Before starting your simulation you should check your mass balance by a quick hand calculation. cheers wikie

 May 5, 2015, 05:15 #3 New Member   Join Date: Mar 2015 Posts: 16 Rep Power: 8 Hello, I have a similar problem. I should simulate flow through 6 boxes stacked upon each other and have an outlet at the top, like a chimney or exhaust. I set 0 relative pressure at the opening of the boxes and a speed at the outlet, the exhaust, but I get that the air only passes through the top boxes. You can see what the system looks like in the attachment. Thanks

 May 5, 2015, 05:28 #4 New Member   Join Date: Mar 2015 Posts: 16 Rep Power: 8 Actually, here is the attachment, CFX Exhaust.jpg

 May 6, 2015, 02:34 #5 Member   Roman Gobitz-Pfeifer Join Date: Dec 2009 Location: Stuttgart Posts: 83 Rep Power: 13 Hi Marko, is your question a general problem with the model setup or a software related problem - I'm asking because your posting an ANSYS screenshot in the phoenics section cheers wikie

 May 6, 2015, 03:48 #6 New Member   Join Date: Mar 2015 Posts: 16 Rep Power: 8 Actually it should have been CFX but I haven't notices I'm on Phoenics forum. In any case it is a setup problem. I should model some flow resistance but I don't see how...

 Tags air flow, air flow simulation, exhaust gas, phoenics vr