Inverted "U" Vent Criteria, Air pockets
Inverted "U" Vent Criteria, Air pockets
(OP)
Hi my friends.
I am looking for some bibliography or texts from where I can exctract some criteria. I need to know in which situations I need to use a vent for normal runing and sistem starting, depending on diameter ,flow rate, pressure and temperature.
Mostly I am searching for norms or bibliography to suport a valid argument depending the case of air acumulation.
Thanks a lot!
Diego Andrés Nitzsche
I am looking for some bibliography or texts from where I can exctract some criteria. I need to know in which situations I need to use a vent for normal runing and sistem starting, depending on diameter ,flow rate, pressure and temperature.
Mostly I am searching for norms or bibliography to suport a valid argument depending the case of air acumulation.
Thanks a lot!
Diego Andrés Nitzsche





RE: Inverted "U" Vent Criteria, Air pockets
RE: Inverted "U" Vent Criteria, Air pockets
Roughly simplifying the pipes could be resumed like this:
Between 2" and 4" 20 000 Kg/h 9.4 mPa
Between 4" and 6" 150 000 Kg/h 0.5 mPa
Between 1.5" and 3" 5000 Kg/h 11 mPa
Any ideas where I can get some criteria reflected on text, norm or paper?
Thanks!!
RE: Inverted "U" Vent Criteria, Air pockets
Thanks a lot!
RE: Inverted "U" Vent Criteria, Air pockets
You need to look up "Froude number" or search for things like "air pipe flow".
Froude number is, in metric, = v / (g x d)^0.5 v, g and d in metres.
The numbers seem to chnge a bit, but all are agreed that for a vertical down pipe, this needs to be > 0.35 in order for bubbles /air to be forced downwards. For a horizontal pipe, to obtain a full pipe, you need a number greater than 1.
In any event whether you actually need air vents depends on your design. If the pipes are all fed with liquid under pressure, then it shouldn't make any difference. It is only if there is a condition where you need to get a syphon going is there a big issue with air vents. However if you are at Froude numbers where there isn't sufficient flow to blow any air bubbles or pockets out on re-start, then you could get two phase or surging flow.
for liquids anything more than about 1m/sec is normally more than enough to sweep air through the pipe.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way