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Thread: Comparative sizes of parts in rebreathers

  1. #11
    RBW Member michael-fisch is on a distinguished road michael-fisch is on a distinguished road michael-fisch's Avatar
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    Re: Comparative sizes of parts in rebreathers

    Quote Originally Posted by John Liddiard  View Original Post
    Real gas laws lead to diminishing returns on higher pressure cylinders.

    A cylinder pumped to 300 bar does not contain 50% more than the same cylinder pumped to 200 bar.

    Up to 200 bar compression is pretty much linear (ideal gas laws). I seem to remember it being about 10% less than linear at 300 bar, so the 300 bar cylinder is only as good as 270 bar if everything were linear (my memory for numbers could easily be wrong).
    Yes and no!
    A 50L cylinder filled to 300Bar with He holds 13200L.
    If you fill it with O2 it holds 15200L at 300Bar, and if you fill it with Ar it holds 15400L.
    If you fill a 50L tank to 300bar with air it only holds 13400L.
    Ideal gas laws only hold up well as long as you are calculating O2, all other diving gasses can be way off.

    Michael

  2. #12
    Photographer & Journalist John Liddiard has a spectacular aura about John Liddiard has a spectacular aura about John Liddiard has a spectacular aura about John Liddiard has a spectacular aura about John Liddiard has a spectacular aura about John Liddiard's Avatar
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    Re: Comparative sizes of parts in rebreathers

    Quote Originally Posted by michael-fisch  View Original Post
    Yes and no!
    A 50L cylinder filled to 300Bar with He holds 13200L.
    If you fill it with O2 it holds 15200L at 300Bar, and if you fill it with Ar it holds 15400L.
    If you fill a 50L tank to 300bar with air it only holds 13400L.
    Ideal gas laws only hold up well as long as you are calculating O2, all other diving gasses can be way off.

    Michael
    Wow, I hadn't realised O2 was that good at 300 bar. My thinking has been clouded by assuming O2 would be similar to N2 (or air). Thanks.

  3. #13
    RBW Member RZEP17 will become famous soon enough RZEP17 will become famous soon enough RZEP17 will become famous soon enough RZEP17 will become famous soon enough RZEP17's Avatar
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    Re: Comparative sizes of parts in rebreathers

    Quote Originally Posted by heyydude  View Original Post
    " The only "civilian" unit I know of that used Spheres was Dan Wible's CCR-2000 that was eventually built by Olympic Submarine - those were the last spheres that Tavco made. Olympic stopped making them quite a while ago, and though Dan sold a number of units (I added a Hammerhead Controller to Tom Mount's personal unit) the CCR-2000 never quite caught on.
    Too bad about CCR 2000 - interesting unit. I attended one of the Dan's presentations, in early 2000s, and it reignite my interest in closed circuits.
    Tomek

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