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Thread: Oval scrubber designs

  1. #1
    RBW Member rian is an unknown quantity at this point rian's Avatar
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    SP Kiss;Home build;Inspiration

    Oval scrubber designs

    I’m planning a new home build re-breather again. Why are the big boys not building a oval type of scrubber, whether it be a axial or radial type? With my preliminary layout drawing I can achieve a much more compact scrubber with the same mass of sorb. Even my bed depth per surface area is less than that of a Insporatio’s.
    What are the draw backs between a oval shaped scrubber as to a cylindrical?

  2. #2
    RBW Member ChristianM is an unknown quantity at this point ChristianM's Avatar
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    Dolphin SCR/CCR

    Re: Oval scrubber designs

    Hi Rain,

    oval scrubber for radial scrubber would be no good idea because for a radial the length of the scrubber would be different.
    And there are oval scrubbers. The Dolphin (so also some of the LAR) is using a oval, axial scrubber.
    I think on thing is that a round scrubber is easier to produce. Just take a pipe and add a base and a head. A oval scrubber must be molded somehow.

    Cheers,
    Christian

  3. #3
    RBW Member Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse's Avatar
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    Re: Oval scrubber designs

    The RGUMF used an oval scrubber.

    I have no idea how the oval shape affects gas flow.

  4. #4
    RBW Member rian is an unknown quantity at this point rian's Avatar
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    Re: Oval scrubber designs

    I was actually hoping that some body has got actual facts available regarding the efficiency of a cylindrical versus the oval shape.
    I must admit that it will be cheaper manufacturing the round shaped scrubber, there are unfortunately no challenge in doing so. I will try to upload my design just for interest sake.Hopefully I will get more positive comments than negative.

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    RBW Member sailor is on a distinguished road sailor is on a distinguished road sailor's Avatar
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    Re: Oval scrubber designs

    Hi,

    as far as I know the sorb efficiency is better with round scrubbers as there is a bigger chance of unused, bypassed sorb in an oval scrubber design.

    Reiner

  6. #6
    Draeger alexander.busch_st is an unknown quantity at this point alexander.busch_st's Avatar
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    Oval scrubber designs

    Hi, I would say it is pretty much a classical trade: Volume efficiency vs. manufacturability.
    The absorption process should not be very dependent on the x-sectional shape.
    See http://www.dtic.mil/get-tr-doc/pdf?AD=ADA160181 for some light reading..



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    Re: Oval scrubber designs

    Quote Originally Posted by alexander.busch_st  View Original Post
    Hi, I would say it is pretty much a classical trade: Volume efficiency vs. manufacturability.
    The absorption process should not be very dependent on the x-sectional shape.
    See http://www.dtic.mil/get-tr-doc/pdf?AD=ADA160181 for some light reading..



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    I assume that the efficiency on the oval is a bit less in cold water, as it is a non-insulated scrubber, so there is some effect of water temperature on the sorb close to the outer walls, and since oval has more surface than round, so a bit more sorb affected by cold water...
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  8. #8
    Draeger alexander.busch_st is an unknown quantity at this point alexander.busch_st's Avatar
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    Oval scrubber designs

    Yeah that is probably correct. I would assume though that one would always try to isolate a scrubber as good as technical feasable. On a well isolated scrubber the difference in endurance is probably rather small?


    Sent via smartphone, please excuse typo-mistakes.

  9. #9
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    Re: Oval scrubber designs

    Quote Originally Posted by alexander.busch_st  View Original Post
    Yeah that is probably correct. I would assume though that one would always try to isolate a scrubber as good as technical feasable. On a well isolated scrubber the difference in endurance is probably rather small?


    Sent via smartphone, please excuse typo-mistakes.
    I was referring to the dolphin scrubber
    on a well insulated scrubber, the difference should be neglectable
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  10. #10
    RBW Member rian is an unknown quantity at this point rian's Avatar
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    SP Kiss;Home build;Inspiration

    Re: Oval scrubber designs

    Thanks for the feedback and the link. Will work through the design criteria for a scrubber. This is my second unit I build from scratch, hope my drawing makes sense?. Cost is actually much less than buying a new one.........you can ask my wife she will confirm.
    The scrubber housing, lid and scrubber itself will be made from carbon fibre and some other types of composites. The scrubber housing wall for instance will be 8-10mm thick and casted under vacuum from epoxy resin. The area where the O-rings seal will be machined to the desired tolerances after words. All material of construction can handle temperatures of -50⁰C, one day I will be able to dive my dream...... Orcas.
    The final machine will have back mounted lungs and the gas will be supplied from 7 / 12l cylinders carried the way you will carry your open circuit bail outs akka side mount style. This setup will leave you with a scrubber on the back measuring 400mm long and 120mm deep. It will also make life much easier getting into the machine on a boat, back here in sunny South Africa we use little rubber ducks to dive from..........live is shit, and the operator needs to load as many possible clients to make money.
    The machine will have 2 x interchangeable in-line, axial scrubbers which will hold 2.7 -3kg sorb total. The void between the scrubbers will eliminate the risk of “channelling”. It seems to me it also increases the dwell time of the gas in the scrubber.
    Attached Files

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