One dead, one missing (since found), 300 foot dive - Lake Michigan

[rjack321]

Here is my guess (as a chemical engineer), cylindrical flow path is more uniformly utilized the bed with constant gas superficial velocity across the bed. While in radial flow path, although you would have shorter travel, the gas superficial velocity would drop as the circumference area increases with radius. The outer radius of the bed may not be fully utilized. It would be different if the torus (donut) shape is rotating where the superficial gas velocity would be in tangential direction as in Rotating Packed Bed process, ANDRITZ Rotating packed-bed centrifuge RPB (the process that I developed with Andritz).

Disadvantages of RPB is it requires power to rotate the bed and a seal between rotor and the housing (though a simple labyrinth type seal can be effectively used in this case). Advantages of RPB is very high absorption efficiency (up to 10 times more efficient than static bed) and the rotation acts as impeller of a blower, reducing WOB.

The RPB can be magnetically driven (mag-drive) by electric motor to avoid mechanical seal.

Axial scrubbers are consumed in a cone shaped manner due to the retention of heat in the center vs the outside edge.
John C Clarke's blog has some good posts about how scrubber's work. This one illustrates the cone
A Look Inside Rebreather Scrubber Canisters, Part 2

 

[uwxplorer]

This is Revo's official position. The practical depth limit is 2 ata about the IP.

In reality O2 flows all the down to the IP, its just getting slower and slower the closer you get to the IP.

fO2 drop in the loop at 300ft is pretty slow though. Going hypoxic at 300ft because your IP "only" 180psi is going to take longer than your bottom time.

Note arguing with the first part. This is Paul Raymaeker's original note on that subject: Understanding Constant Mass Flow • ADVANCED DIVER MAGAZINE • By Paul Raymaekers
As far as the last point, you'll tell that to the guy I was mentioning earlier who decided to abort... He was going down and SAW his pO2 going likewise.

 

[rjack321]

Note arguing with the first part. This is Paul Raymaeker's original note on that subject: Understanding Constant Mass Flow • ADVANCED DIVER MAGAZINE • By Paul Raymaekers
As far as the last point, you'll tell that to the guy I was mentioning earlier who decided to abort... He was going down and SAW his pO2 going likewise.

Descending and ppO2 dropping at the same time? Either his ADV was leaking or something else was wrong like flooding or bad cells. As I'm sure you know, there's no real way to descend and not have the PPO2 rise.

 

[uwxplorer]

Not much ata increase from, say 200 to 220 ft. However, hauling a rebreather, 4 bailout cylinders and a scooter, fighting a possible current (I was at the surface, so I can't speak for that), I wouldn't exclude he burnt more O2 than the <10% pO2 increase due to the descent. I am pulling those numbers off my buttocks obviously.

 

[rjack321]

Oh I gotcha. I dunno I wasn't there. But there's a whole lot of O2 molecules in a revo at 300ft with a ppO2 of 1.2ish. Watching it drop to 1.1 is not going to be fast

 

[cathal]

Descending and ppO2 dropping at the same time? Either his ADV was leaking or something else was wrong like flooding or bad cells. As I'm sure you know, there's no real way to descend and not have the PPO2 rise.

With the rEvo, for the ppO2 to drop at depth, this can be where the unit has not been changed over to eccr, and the ambient pressure is greater than than the O2 I.P.

 

[rjack321]

With the rEvo, for the ppO2 to drop at depth, this can be where the unit has not been changed over to eccr, and the ambient pressure is greater than than the O2 I.P.

Yes but you realize how many O2 molecules are in 8L of CL gas at 10ATA and a ppO2 of 1.2?
8 * 10 = 80L at 1 ATA
10ata / 1.2 = fO2 = 8%
8% * 80 = 6.4L of O2 in there (in surface liters)
That's a lot to metabolize, at least 5mins and that barely accounts for your lung volume.

 

[cathal]

Yes but you realize how many O2 molecules are in 8L of CL gas at 10ATA and a ppO2 of 1.2?
8 * 10 = 80L at 1 ATA
10ata / 1.2 = fO2 = 8%
8% * 80 = 6.4L of O2 in there (in surface liters)
That's a lot to metabolize, at least 5mins and that barely accounts for your lung volume.

Consider elevated respiratory rate when your poO2 starts to drop at 80-90M and you’ll find that ‘5 minutes’ to metabolize 6.4L of O2 is reduced considerably. You can look at realistic bail out SAC’s at this depth for comparison.

 

[Dan]

Axial scrubbers are consumed in a cone shaped manner due to the retention of heat in the center vs the outside edge.
John C Clarke's blog has some good posts about how scrubber's work. This one illustrates the cone
A Look Inside Rebreather Scrubber Canisters, Part 2

Wow! Very impressive computational fluid dynamic simulation. I can see possible CO2 channeling through the cold side (wall) of the bed when you use CCR in very cold water.

 

[KathyV]

Sorry if this is a duplicate post but I came across this article about the accident that was published on friday:

Report details Lake Michigan diving accident in which Illinois couple died