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Thanks Ian & Jim,
I read through that section of "Busby" earlier today.
It states how to calculate the build up of CO2 but doesn't give a
formula
to remove it. It does say on the next page (420) that there is no
conformity
from vehicle-to-vehicle on the type of fan, power of the fan motor or
volume
or configuration of the chemical bed.
In my situation where I am 1 person seated in a stationary position, I
could
have the air intake to the scrubber near my face wich would catch a lot
more CO2
before it circulated.
I'm a little surprised that this isn't as simplistic as I first
thought.
I hadn't heard before that the volume of air flow through the scrubber had
to be relatively
large. It will be a matter of how big my cabin space is & how much flow
is required to
keep CO2 at an acceptable level. & how big & what dimensions my
scrubber / scrubbers
need to be to accommodate the air flow by allowing enough dwell time in the
absorbent.
More calculations.
Regards Alan
----- Original Message -----
Sent: Monday, June 14, 2010 5:05 PM
Subject: Re: [PSUBS-MAILIST]
scrubbers
Alan, you might also consider the location of the exhaust (extension)
from the scrubber as well as the intake so that you don't get short
recirculation from the two being too close together. My thought is that
the further apart you can have them consistent with practicality and the
design requirements of other component of the craft, the better
circulation you will have in the sub for all purposes. However I'm certainly
open to correction.
In your design does the pilot remain approximately in the same
position or move to different locations within the sub?
Jim T
In a message dated 6/13/2010 11:42:08 P.M. Central Daylight Time,
irox@ix.netcom.com writes:
Hi
Alan,
checkout page 419 of Manned Submersibles by Frank Busy.
This gives
some formulas which can be used to calculate the CO2 build up
taking
into account the volume of the pressure hull (well, the
floodable
volume per person). You should be able to find this book
a several
sources online (including psubs I think), this is a great
reference
particularly aimed towards small
submersibles.
Cheers,
Ian.
-----Original
Message-----
From: Alan James
Sent: Jun 13, 2010 10:52
PM
To: personal_submersibles@psubs.org
Subject:
[PSUBS-MAILIST] scrubbers
To
All,
While looking at various papers on CO2 scrubbers
from
manufacturers
etc, I found that none addressed the unique
situation
found in submarines.
Most CO2 absorbent is used in anesthetic machines
or rebreathers where
there is a closed circuit. The CO2 breathed out
goes straight into the scrubber
& is removed.
In our subs
the CO2 is breathed out & is
diluted by the rest of the air in the
hull & only air with a portion of the CO2 in
the hull goes
through the scrubber.
This means that the CO2 level & the pressure in
the hull will progressively climb
unless the volume of air going
through the scrubber
is large enough to make an
impact. The Deep
Worker 2000 has fans pushing 160
liters per minute, I'm not
sure
whether this is per scrubber & whether
they have 2 scrubbers working
simultaneously. But based on 1 fan going, that's
320 x the volume of
CO2 being
produced. In the manufacturers guidelines for
scrubbers
they recommend that the flow
is at least equal to
the tidal volume
of your breath (about 10 liters per minute)
& low enough so that the
air has at least 1/2 a second dwell time in the canister.
This could be
32 x less than what Phil has worked out is necessary for the
Deep
Worker. I know
the Deep Worker has a small hull & that fluctuations
in O2
& CO2 are more critical than a K250, but possibly the same
volume of flow is
necessary to achieve
atmospheric control in
larger subs.
Also because of the dwell time needed the large
flow
required would need large or
long canisters. Deep Worker has 2x 3.35 kg
scrubbers.
On the psub site there is reference to rebreather
cartridges as an option, but from
what I've found you would probably
need a number of
these running simultaneously
to make head
way.
What are ABS recommendations? & what are others
thoughts /
experiences with this.
I'm trying to sort this stuff out for
myself.
Regards
Alan
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