[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PSUBS-MAILIST] scrubbers



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



************************************************************************
************************************************************************
************************************************************************
The personal submersibles mailing list complies with the US Federal
CAN-SPAM Act of 2003.  Your email address appears in our database
because either you, or someone you know, requested you receive messages
from our organization.

If you want to be removed from this mailing list simply click on the
link below or send a blank email message to:
    removeme-personal_submersibles@psubs.org

Removal of your email address from this mailing list occurs by an
automated process and should be complete within five minutes of
our server receiving your request.

PSUBS.ORG
PO Box 53
Weare, NH  03281
603-529-1100
************************************************************************
************************************************************************
************************************************************************