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Tracy Baker wrote: > > I'm playing with some gas mixing algorithms, and I have a couple of > questions... I know the ideal gas laws break down outside of a fairly > narrow temperature/pressure range, and that there are other things I'd > need to take into account to get really accurate numbers for partial > pressure mixing............... > Here in Sweden were 300 bar air tanks are common most divers are unaware of the fact that above 200 bar air statrt to deviate from the ideal gas approximation. Density for air is as follows: T= 290 K (17 C=63 F) P(bar) density(kg*m^-3) change from ideal (my calc.) ======================================================= 1 1.202 10 12.06 0.3% 50 60.90 1.3% 100 121.9 1.4% 150 180.5 1.1% 200 234.7 -2.4% 300 326.8 -9.4% 400 398.6 -17% 500 455.2 -24% 700 538.8 -36% 900 599.5 -45% Source: Encyclopedie des Gaz - l'Air Liquide (Warning! Typing errors not checked) conversion: 1 bar = 1E5 Pa (Pascal) = 14.15 psi = 0.987 atm 1 kg*m^-3 = 0.0624 lbm/cuft The same source has data for many other gases. This is the explanation why my pressure gauge drops so mutch faster the first minutes of the dive. This is allso the reason why AGA (the large Swedish gas company) dropped there plans for 400 bar tanks for firefighters. These tanks would be to heavy, but new composit tanks can make the difference. Sten Meyer (m87stme@mt*.ch*.se*) Chalmers University of Technology
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