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So if a cylinder valve was opened on the surface and then replicated in exactly same way underwater, would the cylinder empty at the same rate or more quickly or slowly under water?
Very slightly more slowly as more external pressure means less net force to drive the gas.
It's a pretty trivial difference at normal diving depths but, of course, at 3kilometers deep it wouldn't bubble at all.
The effects would be very different. The first stage tries to regulate so about 10bar above ambient so theoretically the flow should be roughly constant instead of falling off as the cylinder pressure dropped. Naturally with a hose open it isn't going to be able to regulate but it's going to try but to what level it does is going to be very much dependant of the geometry of the system and I wouldn't like to even guess. Let's just say that with more clutter in the way the gas will flow a bit slower.would there be a different answer is say a second stage was purged ie the loss would be after the first stage pressure adjustment?
Very good Nigel... reminds me of last year when an engineer (don't ya love 'em?) asked me why the diver couldn't pull off a cap at -70m. I took the top off his stainless thermal coffee cup, put it on the deck and asked him if he could prise it off with me standing on it... with two other guys standing on my shoulders? He kind of got the message :wink:The effects would be very different. The first stage tries to regulate so about 10bar above ambient so theoretically the flow should be roughly constant instead of falling off as the cylinder pressure dropped. Naturally with a hose open it isn't going to be able to regulate but it's going to try but to what level it does is going to be very much dependant of the geometry of the system and I wouldn't like to even guess. Let's just say that with more clutter in the way the gas will flow a bit slower.
Divers are very blasé about pressure. Just because we say things like 300 bar to one another doesn't mean we have a clue what it means.
1 bar is 1Kgm per square cm. In believable units a postage stamp is 4sq cms so 300bar on that is about 1200kgs which is an old Ford Escort with the driver sat in.
One tenth of a bar on your chest (say 30x30cms) is the equivalent of having somebody sit on you, one bar is a car, a nice 50bar reserve is a tank, the military version.
Very slightly more slowly as more external pressure means less net force to drive the gas.
Is there not a maximum flowrate depending on the design of the orifice? Or is that maximum too high to consider?The rate of flow of any fluid between two points, is dependant on the pressure difference between those points.
No. You're probably thinking of the trick called the 'sonic' orifice that they use on manual rebreathers to get a constant flow. It makes the flow independent of the pressure it is flowing into.Is there not a maximum flowrate depending on the design of the orifice? Or is that maximum too high to consider?