Re: [PSUBS-MAILIST] internal airflow

["Richard Gordon" <lrrg@wantree.com.au>]

Hi Sean,
I guess the airflow for the scrubber fan should be atleast 1 litre per
minute per person(I think that's what I read). As for the placement of the
intakes and exhausts, the exhaust should probably be as close to your head
as possible (I guess above it would be best). Whatever the compostion of the
air is at your feet doesn't really matter as much as the composition of the
air around your head.

 Even in cramped spaces, vorticies of air flowing around air of different
densities and compositions and tempratures can form 'isolation pockets'
which are pockets of air around which other air flows. The vorticies that
are formed can actually hold an isolation pocket in one place with very
little diffusion of gases. The best way to avoid this is to have both vents
pointed at the most crucial spot, ie. your face. The more direct the
flow-through is, the less chance you have of forming an isolation pocket.
Your CO2 and O2 sensors won't be much use for detecting these pockets unless
they are also close to your head.

Remember that it only takes quite a small fluctuation in the levels of these
gases in the air you breath to effect your spatial ability, orientation
awareness and decision making skills. I guessI didn't really need to tell
you that. My father is a Commercial Pilot, Flight Instructor and a Master of
Engineering, so I guess he's influenced my thorough communication skills.

Rich

----- Original Message -----
From: Sean T. Stevenson <ststev@uniserve.com>
To: <personal_submersibles@psubs.org>
Sent: Saturday, May 19, 2001 9:56 AM
Subject: Re: [PSUBS-MAILIST] internal airflow


> That being said, what are the typical flow rates being used in PSUB
> scrubber fans?
>
> -Sean
>
>
> On Fri, 18 May 2001 21:02:50 -0400, Dan H. wrote:
>
> >If you were looking at a larger space, it might be a consideration, but
in a PSUB there no dead air corners.  I'm sure just the air exiting your
scrubber will cause enough turbulence in a PSUB to mix it up.
> >Put a person in the mix to breath in and exhale, not to mention be moving
around, and I doubt it would make much matter where you placed what.
> >
> >Dan H.
> >
> >"Sean T. Stevenson" wrote:
> >
> >> For those of you with 1 atm scrubbed systems, what if any work did you
do to ensure that the flow of air through the cabin maximizes the
recirculatory efficiency?  I'm working on a conceptual design,
> >> and am thinking of placing the freshly scrubbed air outlets high and
the intake to scrubber low, but I have no idea how to model the airflow.  Do
I even need to worry about this?  Maybe diffusion is fast
> >> enough to take care of the problem.  Thoughts?
> >>
> >> -Sean
> >
>
>
>