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silent running · 26th April 2007, 17:30

Quote: (Originally Posted by AD_ward9)

In terms of using these figures to get the effect in a rebreather, it is a simple process: The maximum breathing resistance is defined in EN14143 (25mbar). It follows basic gas laws, so there is a hydrostatic element (eliminated in EN14143 depth measurements if Over the Shoulder CLs are used because it takes the measurement relative to the suprasternal notch instead of the lung centroid). Alex

Hi Alex, thanks very much for all the good data to chew on. But I've got a few questions:

Can you explain this bit above about the OTC CLs and the "suprasternal notch" and EN 14143 depth measurements being eliminated with OTS CLs?

Do you know how mbars compare to kPA units? I'm not even sure what kPA are, joules maybe?

And you mention in your test that you had 80% humidity in the canister/breathing machine. But isn't the humudity in a CCR loop very close to 100% and wouldn't this have the effect of increasing the WOB and thus effect measured resistive loads and is it necessarilly a linear increase for both EAC and granular as humidity increases?

And while I understand the care taken in your study to islolate the various factors in WOB and the modular nature of the test protocol, I can't help but wonder if you really could just change the maths and plug in a radial. If I'm understanding the basic factors/maths, we would need to know the length of the grain boundry, the overall volume of the scrubber and then factor in the gas flow path, which will be dependent on the proportions. Doesn't seem so simple to me.

And back to Tim's 4 cent analogy, if a same sized radial starts out with a lower WOB to begin with, is that 4 fold increase in WOB due to moisture really that noticeable? To make it more complicated, in my experience with the Prism in-out flow, the sorb clumps up around the inlet tube, roughly evenly top to bottom, which might suggest that exhale resistance could increase a bit and the inhale side might not. Then we have the gas tending to take the path of least resistance and moving around the clumped sorb, which given shorter grain boundry of a radial, would make any WOB increase even less. I myself have not noticed any increase in WOB on my radial until the very end of a long push, but by way of full disclosure, I have been accused of being insensitive by several girlfriends.

EACs look like an attractive alternative to a conventional axial for several reasons, including your findings above relating to the stable WOB throughout the duration. But I doubt that an EAC which takes up the same volume as a properly propotioned, well insulated radial could match it's duration. Then we have the sorb vs. EAC portability issue, the final deal breaker for me... -Andy

Sorry to throw all this at you in one post.... Thanks, -Andy

26th April 2007, 17:30	#37 (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: 1,864	Re: Extendair better for flood recovery? Quote: (Originally Posted by AD_ward9) In terms of using these figures to get the effect in a rebreather, it is a simple process: The maximum breathing resistance is defined in EN14143 (25mbar). It follows basic gas laws, so there is a hydrostatic element (eliminated in EN14143 depth measurements if Over the Shoulder CLs are used because it takes the measurement relative to the suprasternal notch instead of the lung centroid). Alex Hi Alex, thanks very much for all the good data to chew on. But I've got a few questions: Can you explain this bit above about the OTC CLs and the "suprasternal notch" and EN 14143 depth measurements being eliminated with OTS CLs? Do you know how mbars compare to kPA units? I'm not even sure what kPA are, joules maybe? And you mention in your test that you had 80% humidity in the canister/breathing machine. But isn't the humudity in a CCR loop very close to 100% and wouldn't this have the effect of increasing the WOB and thus effect measured resistive loads and is it necessarilly a linear increase for both EAC and granular as humidity increases? And while I understand the care taken in your study to islolate the various factors in WOB and the modular nature of the test protocol, I can't help but wonder if you really could just change the maths and plug in a radial. If I'm understanding the basic factors/maths, we would need to know the length of the grain boundry, the overall volume of the scrubber and then factor in the gas flow path, which will be dependent on the proportions. Doesn't seem so simple to me. And back to Tim's 4 cent analogy, if a same sized radial starts out with a lower WOB to begin with, is that 4 fold increase in WOB due to moisture really that noticeable? To make it more complicated, in my experience with the Prism in-out flow, the sorb clumps up around the inlet tube, roughly evenly top to bottom, which might suggest that exhale resistance could increase a bit and the inhale side might not. Then we have the gas tending to take the path of least resistance and moving around the clumped sorb, which given shorter grain boundry of a radial, would make any WOB increase even less. I myself have not noticed any increase in WOB on my radial until the very end of a long push, but by way of full disclosure, I have been accused of being insensitive by several girlfriends. EACs look like an attractive alternative to a conventional axial for several reasons, including your findings above relating to the stable WOB throughout the duration. But I doubt that an EAC which takes up the same volume as a properly propotioned, well insulated radial could match it's duration. Then we have the sorb vs. EAC portability issue, the final deal breaker for me... -Andy Sorry to throw all this at you in one post.... Thanks, -Andy
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