I have had the same experience and agree with you.
Alton

"David B. Widen" wrote:

> Alton
>
> I'm with Jim on this one. You can have all the subject matter experts,
> theory, math, periodic tables to argue the thermo point. I know from
> personal experiences that when the helium rich mix hits my chest in the dry
> suit, I get a cooler feeling then when air or argon is used - period. I am
> colder at the end of the dive when a helium rich mix was used - dumb on my
> part. Did it once and won't do it again.
>
> David
>
> >-----Original Message-----
> >From: Alton J. Hall, Jr. [mailto:ahall@da*.co*]
> >Sent: Tuesday, February 20, 2001 1:39 AM
> >To: Jim Cobb
> >Cc: Matthias Voss; moorea(uol); techdiver@aquanaut.com
> >Subject: Re: More about breathing Helium thermal loss
> >
> >
> >For what it is worth, I recently was involved in a case in
> >which the thermal
> >capacity of Helium and it's effect on a diver breathing it
> >(i.e. it's insulation
> >qualities were not discussed) was debated between two experts.
> >In the final
> >analysis the experts opinion was that the effect was minimal if any.
> >
> >Alton
> >
> >Jim Cobb wrote:
> >
> >> Matt-
> >>
> >> Damn engineers... ;)
> >>
> >> The point is that often I see folks on this list delving
> >into the obscure
> >> theory behind this and that but miss the big picture. By the
> >way you seem to
> >> be saying that helium is a good heat transfer medium in
> >addition to being a
> >> poor insulator, I really can't wrap my brain around this
> >one. And can we
> >> really use gases that get warm on expansion for diving? You
> >worked up tables
> >> for them yet?
> >>
> >> Like I said, I am no physicist (or engineer) but have
> >certainly felt the icy
> >> cold blast of air out of a regulator chill me to my bones.
> >It feels good in
> >> the summer and like death in the winter.
> >>
> >> Hows this for an engineering project, take an ice diver with
> >a frozen first
> >> and the have him thaw it by breathing on it. Then compare
> >the time it took
> >> for the first to freeze and compare how long it took for it
> >to thaw from him
> >> breathing on it. At least you will get a dive out of it.
> >>
> >>    Jim
> >>
> >>  -------------------------------------------------------------------
> >>  Learn About Trimix at http://www.cisatlantic.com/trimix/
> >>
> >> > From: mat.voss@t-*.de* (Matthias Voss)
> >> > Organization: Harry Haller Memorial Fund
> >> > Date: Wed, 21 Feb 2001 19:25:38 +0100
> >> > To: Jim Cobb <cobber@ci*.co*>
> >> > Cc: "moorea(uol)" <moorea@uo*.co*.br*>, techdiver@aquanaut.com
> >> > Subject: Re: More about breathing Helium thermal loss
> >> >
> >> > Jim,
> >> >
> >> >
> >> >
> >> >> On a more practical note, when breathing open circuit, as the gas
> >> >> expands from the tanks to the outlet of the second stage,
> >it cools.
> >> >
> >> > Some gases, like nitrogen, Oxygen, do. They do it within
> >the limits of
> >> > our diving environment. That is, bottle pressure 50 to
> >200bar, ambient
> >> > pressure from 1 to 15 bar, ambient temperature from zero to 30 °C.
> >> >
> >> > Other gases do not. It is rather fizzical, but there are
> >gases which get
> >> > warmer when they expand , in our kind of settings. In
> >other settings ,
> >> > any gas does. They just show a different behaviour
>
> >cooling or heating)
> >> > for different pessure/ temperature settings). I have to
> >look it up how
> >> > much helium is concerned here, but is definitely plays a role.
> >> > For the temperature effect, remember that the heat
> >capacity refers to
> >> > mass, not to volume. We breathe volume, though, so please
> >adjust the
> >> > math to that.
> >> >
> >> > The real issue about heat loss is, we do not have
> >temperature sensors in
> >> > our lungs ewhich tell us we should warm up a bit. This may lead to
> >> > dangerous lowering of body temperature, apathy, drowsiness.
> >> >
> >> >
> >> >
> >> >> This is the same principle that air conditioners work on.
> >> > Well, yes. But these work with gases ( freon) which dangle
> >near their
> >> > point of condensation)
> >> >
> >> >
> >> >
> >> > This would
> >> >> be the primary source of heat loss rather than the
> >composition of the
> >> >> gas being breathed.
> >> >
> >> > I feel the prime source is evaporation of water. Anybody
> >care to do the
> >> > calc?
> >> >
> >> >>
> >> >> If you have ever tried a rebreather, one thing that immediately
> >> >> strikes you is how warm and humid your breathing air is.
> >> > This pertains to mix as well.
> >> >
> >> >
> >> >
> >> > Another
> >> >> comment is that thermal transfer infers that you are
> >moving heat from
> >> >> A to B, certainly not a factor when the heat has nowhere
> >to go, i.e.
> >> >> inside your lungs. While in a drysuit the transfer is
> >from your body
> >> >> to the water which surrounds you.
> >> >
> >> > In a rebreather , B is the water surrounding the loop.
> >> >
> >> >
> >> >>
> >> >> As far as gas of various mixtures acting as a heat transport
> >> >> mechanism, the expansion cooling effect has far more
> >consequences on
> >> >> heat loss on a diver than the composition of your
> >breathing gas to the
> >> >> point of rendering it inconsequential.
> >> >
> >> > Could you prove that ?
> >> >
> >> > Matthias
> >> > ( no physicist, only an engineer)
> >> >
> >> >
> >> >
> >> >> I am no physicist but this seems to be fairly obvious to me.
> >> >>
> >> >> Jim
> >> >
> >>
> >> --
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