air evacuation flow rate help

[yoss]

I'm trying to do a calc to determine the flow velocity expected during evacuation of a dry laminate layup under vacuum bag prior to resin infusion.

i guess i can simplfy the problem down to... sealed chamber volume (0.32 m3) initialy at atmospheric pressure connected to a 200m3/hr pump via 25mm ID pipe.

any tips would be great - can i use benouli or does the flow choke (i have vague memory of this being an issue from uni dayz!)

 

[quark]

Flow is never choked in vacuum systems(or atleast I never heard it). You can use the simple equation Q = Pi/4xd[sup]2[/sup]xV to check the maximum velocity(i.e during initial pull down)which comes out to be around 113m/s...wow.