Re: [PSUBS-MAILIST] Life Support

[Carsten Standfuss <Merlinsub@t-online.de>]

Hi Daniel, 

you need about of 0,5 L/min or 30 L/h of Oxygen per person. 
And about 0,6 kg o2 scruber an hour.  

1.) Scrubber system : 
A Bottle wit 50 l x 220 atm. = 11000 Liter cost 23 euro or 28 USD. 
For 72 Hours you need 30 x 72 = 2160 liter oxygen or 6 USD. 

for 72 hours you need about 0,6 x 72 = 43 kg CO2 scrubber. 
with 18 kg cost about 88,5 euro or 108 USD. 
43/18 x 108 = 258 USD. 

So total is 264 USD or 3,66 USD/hour. 

2.) Fresh air compressor system
For the idear with blowing air into the cabin you need about 25 L/min 
of airflow into the cabin and per person - so 1500 l/hour. 

For 72 hours you need 1500 x 72 = 108000 liter of air compresed into 50
liter air tanks at 220 bars that is: 10 man high Bottles with a volume
and displacement of a half ton (of freshwater).

My air compressor runs 60 liter min or 3600 l/hour and needs 3 kw of
electric energy to do this - there for to remove the 108000 it needs a
run time of 108000/3600 = 30 hours or a storage energy of 3 kw x 30 h =
90 Kwh. This battery weights about 2,4 ts. In real life close to 3 ts. 
This batty will cost about 20000 USD.. Add some 2500 for the air tanks..

After the dive of 73 hours you have to refill the airtanks with 108000
liter of compressed air - needs another 30hours compressor run time. 

The calculation shows not how deep the sub was. Near the surface the
energy for the compressor is much lower. So figu is for higher depths.. 

So system one ist abou 45 kg and 264 USD 
and system two is about 3,5 ts and 22500 USD..  

The problem on the second system is that 97% of the gas you blow into
the cabin and later remove it with a compressor is not useful to breath
it.. is nitrogen and not used oxygen. 

Best regards Carsten

daniel@tordaca.com schrieb:
> 
> Hello every one, since i´m almost done with the construction of my
> k-350, i´m starting to think about life support for it, and me and my
> friend ronny came out with this:
> 
> the cabin of the k-350 holds air enough for two people for about 1
> hour, then as captain kittredge says i should surface and ventilate
> the cabin air, for this i don´t need any equipment, just the air
> trapped inside the cabin before closing the hatch. i wasn´t so sure
> about that so i followed the link to the extended air site and visited
> their store, at the end of the page there is a program that calculates
> the o2 and co2 levels in a confinated space, the cabin area of my
> k-350 is about 60 FT3, in order to use their software i tiped 1 in the
> "L" space, 1 in the "W" space and then 60 in the "H" space, i did this
> becouse their program is built for square spaces and my sub is
> cilindrical, so i calculated my sub volume in the same unit of the
> program (FT3) and then multiplicate it for 1 and for 1 again. the
> aswer was what we all expected, i don´t need to use their kit for the
> first hour, and then i will have to use their kit for the following
> six hours, and if i plan to stay longer i will have to use a
> replacement every six hours, of course i dont intend to be sumerged
> for days, but i was hoping to have a 72 hours life support system in
> case of emergency. the kit cost 350$ and each replacment cost 250$. so
> if i intend to have this this system installed in my sub i will have
> to spend 350$ for the kit and 250$ x 11 = 2750, that´s a total of
> $3100.
> 
> so here comes the idea, if i don´t want to spend this money i will
> have to surface every hour and ventilate the cabin air but if there is
> an emergency and i can´t surface i need to be able to ventilate the
> cabin underwater, for this i have a very simple system in mind:
> 
> imagine a scubba tank filled with air (not O2), like scuba divers use,
> and this tank is constatly bleading air into the cabin in small
> portions, (i haven´t calculate the air flow yet...), then i will have
> a pressure sensor that will activate a small 12 volts compressor to
> suck the cabin air and expel it to the ocean, i know the description
> of this system is very poor and is not technical but i think it will
> work for the following reasons:
> 
> 1) the cabin air is being ventilated constantly, so the air inside the
> cabin is always breathtable
> 2) the pressure sensor will acitvate at 5 PSI, and will shut it down
> at 1 PSI, at this pressure humans don´t have any nytrogen absortion
> problems
> 3) the O2 level should remain within acceptable levels because we are
> bleading air into the cabin not O2
> 4) the CO2 level should remain within acceptable levels because the
> cabin air is bein constantly changed, by this i mean that the
> compressor sucks the breathed air and the thanks bleeds new fresh air
> into the cabin
> 5) the contamination of the air by oil (added by the compressor) is
> not a problem because this breathed and oil contaminated air is being
> expelded out of the cabin, the reason for using a compressor is to
> defeat the outern pressure and be able to change the cabin air.
> 
> i know there is a lot of people in this forum that are experienced in
> this matter so please let me know what you think.
> Best regards
> Daniel
> 
> 
> 
> 
> 
> 
> 
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