I read all my emails in plain text! And no fancy stuff... microsoft outlook
2010... no extra language packs installed... I havent had one of those
prompts yet but I do remember seeing them with outlook express from
memory,
and its got something to do with the character set, or the email client
settings... Possibly the linux box! :)
Stew
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
Sent: Thursday, 17 March 2011 8:30 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Humidity control
Hi Sean ,
I'm still getting the Arabic prompt, doesn't seem anyone else is.
I asked about the ADS system because I'm building a very small sub & would
have similarly fast atmospheric changes. However in an ADS suit it
doesn't
seem that you can do anything to compensate for any problems that may
arise.
After all your arms are entrap, you can't even scratch your nose.
Regards Alan
----- Original Message -----
From: "Sean T. Stevenson" <cast55@telus.net>
To: <personal_submersibles@psubs.org>
Sent: Thursday, March 17, 2011 7:58 AM
Subject: Re: [PSUBS-MAILIST] Humidity control
I have no idea about the Arabic language prompt - I don't know Arabic, and
certainly don't type emails in it. I do send emails from both a Linux
machine
and a windows machine - don't know if that has anything to do with it.
Is
anyone else seeing this?
I try not to use jargon that a layperson could not understand, so if I
have
said something confusing, let me know and I will attempt to clarify. One
of
the best pieces of engineering advice I ever received was "If it can't be
explained in a single sentence, it probably won't work". A gross
simplification for sure, but fundamentally a good idea.
Life support in an ADS is no different than that in a submersible, other
than
its size. Scrubber to remove CO2, oxygen addition system, filter for
trace/contaminant/odor removal, appropriate thermal insulation,
consideration
of air flow path (to ensure effective scrubbing and prevent viewport
fogging,
hydration and waste management, etc. The most difficult part of
designing
such systems is not necessarily the base functions, but rather
accomplishing
those functions in a small and elegant form factor with low power
requirements.
-Sean
On Tuesday 15 March 2011 20:26:57 you wrote:
Hi Sean,
when I go to open your emails outlook express asks me to install an
Arabic
language package, will that help me translate some of your technical
terms???
You were looking at building a deep diving suit. Am wondering what sort
of
life support system they have. Regards Alan
----- Original Message -----
From: "Sean T. Stevenson" <cast55@telus.net>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, March 16, 2011 4:04 PM
Subject: Re: [PSUBS-MAILIST] Humidity control
> Not being a sub owner, all I can offer is conjecture, but I will agree
> that vessels with small energy budgets will have a difficult time with
> this, as heating and cooling tend to constitute large power draws.
>
> If you are operating in cold water, the problem is a bit simpler to
> address, as it is relatively easy to insulate the hull with the
> exception of the bilge in order to purposefully condense water on that
> surface and lower the RH, or to set up some sort of heat exchanger /
> keel cooling arrangement with a condensate drain to do the same. In
> warmer water, this is much less effective.
>
> There are only two practical ways of removing moisture from the air:
>
> 1) cool the air, reducing its moisture carrying capacity and forcing
> it
> to condense, or
>
> 2) Use hygroscopic materials / desiccants to absorb the moisture.
>
> I don't have much familiarity with water absorbing materials, but
> certainly it would be possible to set up a moisture "scrubber" using
> desiccant media which is replaceable just like your CO2 scrubber. Of
> course, you run the risk of having cabin air which becomes
uncomfortable
> because it is too dry, so it would need to be carefully designed to
> match the vessel's size and crew complement. Note also that using
> extremely dry oxygen in your life support system will help to reduce
> RH
> as it is added to the cabin air.
>
> If you cool the air, you can condense out some water, but air in a
> passive condensing apparatus is still at 100% RH until it is
> subsequently heated beyond the condensation temperature. This will
> happen as it mixes with the other air in the cabin, or when heated by
> other sources (i.e. CO2 scrubber is exothermic, electronics will give
> off heat, and occupants give off heat). You need to maintain the
> cabin
> air at a comfortable temperature for the occupants, so the net heat
> gain/loss in the cabin needs to be carefully designed. As far as
> preventing viewport fogging, if you are going to direct airflow
> against
> the windows for this purpose, it should ideally have low relative
> humidity. Condensation occurs when the air in close proximity to the
> window cools and dumps its moisture, so you can avoid this by
> maintaining a constant airflow across the window, but then you
> increase
> convective heat loss and cool the air in the cabin. The drier the air
> flow against the window, the slower it can be and still prevent
> condensation, and the slower it is, the less cooling effect it will
have
> on the cabin air. In a high humidity cabin, one possible flow path
> would be through your condenser to remove moisture, then through your
> scrubber where the slight heat from the exothermic reaction will keep
RH
> below 100%, but the still relatively high RH is actually advantageous
to
> the reaction, then to your electronics etc. to hopefully gain heat and
> lower RH, and then into the cabin via defog ports near your windows.
>
> Even if you don't painstakingly design to keep RH around 50%, at
minimum
> it is important to try to keep it below 100%, not only because this is
> generally uncomfortable for the occupant(s), but also because
> condensation causes corrosion, and certainly may lead to failure of
> electronic components. The only liquid water in your sub should be
> water that was designed to be there.
>
> -Sean
>
> On Tuesday 15 March 2011 11:51:32 you wrote:
>> Sean,
>>
>> To pick up on humidity control in general which you mentioned: This
is
>> a topic which affects a number of things in a sub other than scrubber
>> performance and it's worthy of its own thread. In a small one or two
>> man sub powered completely by batteries it seems to be difficult to
>> manage. I'd be very interested in what anyone has to offer on the
>> topic. We've had a prior discussion on a portable cooling unit
>> which
>> would condense some of the cabin moisture.
>>
>> Thanks,
>> Jim
>>
>>
>> In a message dated 3/15/2011 12:25:50 P.M. Central Daylight Time,
>> cast55@telus.net writes:
>>
>> In a submersible, the problem is more easily avoided, since it takes
>> some time
>> for the cabin air to get close to 100% RH, and there are ways a
>> designer can condense out or otherwise remove moisture from the cabin
>> air to push it down.
>> ABS standard is a relative humidity between 30 and 70% RH, and this
is
>> probably what you should shoot for. (50% RH is often quoted as a
>> desirable target for human comfort in terrestrial buildings).
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