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On Wed, 16 Aug 1995 UHAP010@al*.rh*.ac*.uk* wrote: > > "R_LAROCQUE (418) 775-0792" <r_larocque@AM*.QC*.DF*.CA*> writes: > > > > Whenever I get below 130 fsw in cold water (4degC), my Poseidon Odin starts > > blowing bits of ice down my throat. I know that a few people on this list have > > mentioned this "problem" before but I'm still not sure of the cause. Is it > > due to moisture in the compressed air? or is it condensation from the exhaled > > air? Is it normal? Can something be done about it? Of the regulators I have > > used, the Odin is the only one that does this. > > > > Thanks to all > > > > Richard > > > > >So do mine. I don't think there is anything that can be done, you just > >have to live with it. Anyway these ice bits are quite harmless as they are small > >and melt very quickly. > > >Michael Walz > >walz@la*.ep*.ch* > Hi > Discussion on the list seem to be a bit on the low side - everybody diving???? > But the issue of cold water diving with the high performance DV > (this is what it is) like ODIN may give us a bit of refreshing breath (summer > in UK is unbelievable this year , just came back from a week on the North Sea diving -couple of wrecks). > What we have here is a classic case of high performance demand valve dived > in cold water where large amount of gas (air - and this is important) is > undergoing what is well known as Joule-Thompson transition. Without going > into much of physics this is basically an effect of cooling while gas pressure > is dropping from say 200 bar to 10 bar(intermediate). This is so called > integrated J-T effect and roughly for air we can have 0.17 degree C drop for > an every 1 bar difference between High and interm. pressures in this particular conditions. This will give > you quite a drop well below freezing point. The other problem, of course, is that as good as Poseidon's are, they breathe wet because much of the air escapes from an upward pointing flap valve. The rim of the diaphragm is the exhaust valve, it opens on the top, and some water gets in. Tilt your head with the diaphragm down and completely horizontal so that there is no up, and the effect is lessened or eliminated.
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