Vent Hole
Vent Hole
(OP)
A unit is being designed out of aluminium, and will have a lid to cover the main enclosure, but not sealed. The box needs to have a vent hole in it to ensure there is no pressure build up inside the unit. The vent hole has to meet the following requirements:-
Maximum pressure decay rate of 70 mbars/sec.
Pressure decay of 0.8 bar in 27 sec.
The volume of air inside the box is 200000mm^3
Any ideas?
Thanks
Maximum pressure decay rate of 70 mbars/sec.
Pressure decay of 0.8 bar in 27 sec.
The volume of air inside the box is 200000mm^3
Any ideas?
Thanks





RE: Vent Hole
RE: Vent Hole
This sounds safety related. Is anyone going to answer a question like this without seeing all the drawings, visiting the site, charging a fee, and perhaps putting his license on the line?
--
JHG
RE: Vent Hole
Anything you are doing to intentionally limit the pressure reduction rate means that if something happens to increase the pressure buildup rate, you will end up with an unsafe overpressure condition. Sounds like you'll probably need an additional safety release valve that can vent gas at least at the maximum possible forseeable rate of gas entry.
Wow, only 200,000mm^3? So if it were a cube, just over 2 inches on a side? That's really pretty small.
-handleman, CSWP (The new, easy test)
RE: Vent Hole
Thanks
RE: Vent Hole
-handleman, CSWP (The new, easy test)
RE: Vent Hole
Is there any formula for making a calculation on this?
Thanks
RE: Vent Hole
This is why I said you will need to find out the conditions under which adherence to spec will be verified. You could work on the math and fluids for a week and get a pretty answer, just to find out that the spec is poorly written and nothing like the actual requirement. GIGO. I feel your pain. Unfortunately, specs are not the same thing as requirements. A spec is just a representation of the underlying functional requirement.
-handleman, CSWP (The new, easy test)
RE: Vent Hole
The box needs to have a vent hole in it to ensure there is no pressure build up inside the unit".
Please explain how can there be a pressure buildup given you are VENTING from atmospheric to atmosphere? Air is always going OUT of the unit.
RE: Vent Hole
That's great.
Except that you have no requirements.
The information that you have provided is incomplete, thus no one can provide any useful guidance.
The general form of the orifice flow equation for air is:
Volumetric Flow = A Constant X Orifice Area X Orifice Coefficient X SQRT(Differential Pressure)
As you can see, it's not possible to fill in all the blanks with what you know.
RE: Vent Hole
RE: Vent Hole