Anyone up to “no good” with design ideas?

paulraymaekers

try to do the exercise with the moving front of the used-unused sorb, not as a line, but as a zone of say 10cm long, and you see the difference
it is always so that the second half of the scrubber is used a bit, in the single as well as in the multi-compartement scrubber

regards
paul

decoweenie

How did you come up with 10cm wide as the moving front ?

Was it from measuring an array of thermosensors ?

To be honest, I wouldn't know any better concerning the frontal width, but 10-cm/4-inch sounds a bit wide in my mind. Of course, I believe the frontal width also depend on the scrubber diameter.

IIRC, the frontal width for something very wide like the MK-15 scrubber is quite thin (as according to the "experts" I spoke to )

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paulraymaekers

the front used-unused sorb is never a staight line, it is a zone and depends on lot's of factors:

gasspeed (high speed, large frontzone)
(why would something like 'dwell-time' exist, if the moving front was a line: a line means that all the CO2 is absorbed immediately when gas enters the 'unused' zone of the scrubber, would mean contact-time=near zero :-)
(only gas that is in contact with the sorb will give up it's CO2, and more when the CO2-load is higher, so you need 'mixing'time)
(also: a line would mean that breaktrough would happen in very short time, from 0%CO2 to full CO2 (non scrubbed) that is never the case: CO2 at the output follows a slowly rising curve, and breaktrough is said at 0.5% in the tests)

temp: (low temp, large frontzone)
saturation of scrubber
high CO2 load

I remember some graphs form early US-navy tests, I did some temp tests myself (but not much: it is not easy to perform correct tests :-)

conc MK15: front is shorter: reason: very wide scrubber, so LOW gas speed, but this means that the breatktrough is more abrupt

so for scrubbers, lenght of front-zone depends on where you put the end 0.5% or 0.2% or 0%...

at 0%, the zone is the total length of the scrubber :-)

paul

decoweenie

Paul,

No one said the frontal was a flat line, we agree on that.

For discussion sake, there should be a "line" where the sorb is completely used up, unless there is evidence that sorb can't be 100% completely exhausted. But that is not what we are discussing...

On second thought, I guess my question about the 10-cm/4-inch you quoted was not clear...

IMHO, the reactive zone in the scrubber should be the entire scrubber length from the entrance to the last piece of sorb. The amount of sorb "used up" along this length is inversely proportional to the distance from the entrance (i.e. furthest from entrance = used up less). And this amount is continuously decreasing as more sorb is completely used up near the entrance during the dive.

That's why the entire scrubber is warm and not just part of it. But it is actually the temperature gradient should be hotter near the entrance (i.e. near the border where sorb is completely "used up") at the beginning and moves toward the end.

So I always envision the APV scrubber stick actually measuring the "cold" front, and not the "hot" front. Cold front represents the "line" separate the completely "used up" sorb and the sorb which still has some capacity of scrubbing. The completely "used up" sorb is no longer chemically active, thus not producing heat any more...

That's why I was wondering why you feel that the front is 10-cm on your unit ? Just curious...

The rest concerning the relationship between the break-thru and scrubber diameter, etc is already well known.

__________________
"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

- Rebreather World PM

paulraymaekers

hello deco, the 10cm is just an example, it will vary according to diff parameters


IMHO, the reactive zone in the scrubber should be the entire scrubber length from the entrance to the last piece of sorb.

I don't think that is possible: if that would be the case, breaktrough would happen from the beginning: why would just the last amount of CO2 be absorbed by the last grain of sorb, ... :-) you would be lucky :-)

The amount of sorb "used up" along this length is inversely proportional to the distance from the entrance (i.e. furthest from entrance = used up less). And this amount is continuously decreasing as more sorb is completely used up near the entrance during the dive.

-> deduction 'ex absurdo': so how would it be possible that after some time (when the first 5 cm of the scrubber is not active anymore, that the rest of the scrubber can now scrub all the CO2 over the whole length (wich is shorter now), and so that all CO2 is scrubbed out just at the end of the scrubber?

That's why the entire scrubber is warm and not just part of it.

no, I don't think so: the reason for the entire scrubber being warm is NOT because the scrubber is active over the whole length, but because heated gas from the active zone is travelling trough the unused, not activ sorb and heating up this part of the scrubber!


So I always envision the APV scrubber stick actually measuring the "cold" front, and not the "hot" front. Cold front represents the "line" separate the completely "used up" sorb and the sorb which still has some capacity of scrubbing. The completely "used up" sorb is no longer chemically active, thus not producing heat any more...

I agree with that, problem is that you can not so easely determine the length of the active zone :-(

regards
paul

decoweenie

True. Oh well, time to do some more rethinking...

__________________
"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

- Rebreather World PM

Crazyduck

Paul,

Thank you for joining in the conversation.

Very interesting unit you have created there sir.

Would you consider posting some pictures of the unit in the gallery? I am interested that you mentioned there was no internal plumbing or piping. What did you use for the internal counterlungs?

Thanks again, Andrew

paulraymaekers

I am interested that you mentioned there was no internal plumbing or piping. What did you use for the internal counterlungs?

hello andrew,

gas routing: exhale P-connector, exhale lung (at this moment silicon tissue, later polyurethane), exhale scrubber, cover of scrubbers=mixing chamber, inhale scrubber, inhale lung, inhale P-connector

the openings from lung to scrubbers are diameter 150mm, no restriction at all

I'll post some pics in the gallerie, but first one week farasan banks (KSA) (deep testing rEvo II), then 10 days egypt (deeper testing rEvo II :-)

regards
paul

divetheworld

Now here is a man you can have a sensible conversation with.


Here are the pictures you wanted I think.
http://www.fr.smartgroups.com/pictu...AlbumID=4443689

http://www.fr.smartgroups.com/pictu...AlbumID=4322665



I have been told there is a price attached to thse units, in kit form of course!!

__________________

paulraymaekers

hello , all the above pictures are of the prototype and the rEvo I

these pictures are of rEvo II:

http://www.fr.smartgroups.com/pictur...lbumID=5753865

??? I do not not know about a price for the unit in kit form :-)

anyway, they are not available at this time, all the beta-serie is allocated to different divers

I eventually will sell my rEvo I, but not yet

paul