Rebreather World - View Single Post - dwell-time calculation: axial vs radial

silent running · 5th January 2007, 10:14

Quote: (Originally Posted by paulraymaekers)

hello dave, this type of non-uniform gas-speed distribution is not taken into account, but this does not influence the 'overall' dwell time, as the scrubber is not a 'gas stocking device'

I will not restart the debate about dwell-time, I made my point and I know what I know...

But as you all know, I never said that a radial can not be more efficiant than an axial, I think we all agree on that. But this is due to other factors, like thermal design (isolation), non-uniform gas-flow due to 'water-stocking' in the sorb, non-uniform sorb packing due to position of the cannister during diving etc etc etc

regards
paul

Hi Paul, granted the better insulating qualities of radials are part of increased efficeincy, but do you really think that the rest of the increased efficeincy is only do to such vaugeries like "water stocking"-I assume you mean the swelling of the used sorb-or non-uniform packing? And how do either of these things exist outside the realm of actual dwell time? Seems to me that water stocking is likely to force a tighter, more uniform pack as the sorb expands and would influnce the non-uniform packing and thus increase dwell time. But then again, why wouldn't that also be true for an axial?

Also, anything that decreases the chance of channeling would also increase efficeincy and there is much less hard surface on the outside of a radial canister and the gas is traveling at 90 degrees to the canister wall as opposed to running along parallel to the canister wall in an axial.

Then there's WOB mystery: If a radial has less resistance, it should have less dwell time and be less efficeint than an axial of the same weight, yet this is obviously not true. Judging by the use patterns of in-out radials the bulk of the scrubbing is being done on the exhale side. If the velocity is the same in both kinds of scrubber, how is this possible?

I'm also wondering how much time the sorb needs to bond with the CO2, that would be another clue about how the 2 designs differ and how much the tidal cycle plays in the performance of each design.

Don't get me wrong, I appreciate you putting up the data/model and I'm not trying to be contrary for the sake of it, I'm just not convinced of the relevence of the data/info to the actual real life performance of the designs and I think there are still more questions than answers at this point...

5th January 2007, 10:14	#12 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,873	Re: dwell-time calculation: axial vs radial Quote: (Originally Posted by paulraymaekers) hello dave, this type of non-uniform gas-speed distribution is not taken into account, but this does not influence the 'overall' dwell time, as the scrubber is not a 'gas stocking device' I will not restart the debate about dwell-time, I made my point and I know what I know... But as you all know, I never said that a radial can not be more efficiant than an axial, I think we all agree on that. But this is due to other factors, like thermal design (isolation), non-uniform gas-flow due to 'water-stocking' in the sorb, non-uniform sorb packing due to position of the cannister during diving etc etc etc regards paul Hi Paul, granted the better insulating qualities of radials are part of increased efficeincy, but do you really think that the rest of the increased efficeincy is only do to such vaugeries like "water stocking"-I assume you mean the swelling of the used sorb-or non-uniform packing? And how do either of these things exist outside the realm of actual dwell time? Seems to me that water stocking is likely to force a tighter, more uniform pack as the sorb expands and would influnce the non-uniform packing and thus increase dwell time. But then again, why wouldn't that also be true for an axial? Also, anything that decreases the chance of channeling would also increase efficeincy and there is much less hard surface on the outside of a radial canister and the gas is traveling at 90 degrees to the canister wall as opposed to running along parallel to the canister wall in an axial. Then there's WOB mystery: If a radial has less resistance, it should have less dwell time and be less efficeint than an axial of the same weight, yet this is obviously not true. Judging by the use patterns of in-out radials the bulk of the scrubbing is being done on the exhale side. If the velocity is the same in both kinds of scrubber, how is this possible? I'm also wondering how much time the sorb needs to bond with the CO2, that would be another clue about how the 2 designs differ and how much the tidal cycle plays in the performance of each design. Don't get me wrong, I appreciate you putting up the data/model and I'm not trying to be contrary for the sake of it, I'm just not convinced of the relevence of the data/info to the actual real life performance of the designs and I think there are still more questions than answers at this point...
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