Expedition-level Mk 15.x MCCR in 90 seconds!

Skipbreather

Kent-

Absolutely sweet! Warms the cockles ‘o me heart! Just what ballpark of “expensive” are we talking about?

(WTF IS a cockle, anyway? )

Best,
Ken

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"Entropy RULES! Enjoy the interim."

Rebreatherlab

Hi Skips,

I have sent a quote request to the Parker boys. Will post it here unless Techsimple beats me to it. I think I will order one just for the odd chance it actaully does what everyone hopes it does.

Andy

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www.rebreatherlab.com

teksimple

Yes to both. I think you are right in that it keeps flow constant based on varying downstream pressure differential, not the upstream pressure. But that is what a regulator is for. With a standard depth-compensating 1st stage which keeps the pressure differential constant, I have observed the mass flow to be extremely accurate at any depth.

Price? Something like $800.00 including the Swagelok parts.

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"I don't know the percentage of the Internet that's valid, do you? Jesus, it's scary." - Hunter S. Thompson

paulraymaekers

are you saying that the flow is the same at surface and at 100m??
(withouth adjusting)

paul

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www.rEvo-rebreathers.com

.... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...

teksimple

Yes, that is exactly what I am saying. Now, I have only done one dive below 100m with the Msense, so I do not have a very large N value nor do I carry a flow meter with a graduated cylinder to test it. Since I am not selling the Msense I have no stake in your life. I would recommend going over the pressure numbers with the engineers at Porter (owned by Parker). They will say that it was not designed to go underwater (as was obvious with the rusty screws before I replaced them) but that it is designed to give a very accurate constant mass flow. 1% accuracy is certainly fine in my book.

"A laminar flow element is a constriction consisting of a tube bundle or parallel plates used to measure flows with low Reynolds numbers. The differential pressure across this flowmeter is linear with flow." Thus flow rate with a laminar flow rate is not dependent on ABSOLUTE pressure.

Here is some fluid dynamics background which describes laminar flow elements well.

The question that I want to know is, why hasn't this been adopted by rebreather manufacturers before? Surely the only reason can't be cost?

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"I don't know the percentage of the Internet that's valid, do you? Jesus, it's scary." - Hunter S. Thompson

teksimple

You crack me up!

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"I don't know the percentage of the Internet that's valid, do you? Jesus, it's scary." - Hunter S. Thompson

teksimple

No, you are not being thick, that is a good question. However, you may wish to study the principle of a laminar flow element (I provided a link above) and plug in the numbers yourself in a thought experiment. In our application, by keeping the pressure differential constant, the laminar flow element maintains the constant mass flow. Of course there are other variables which may change the gas viscosity characteristics such as temperature, but for our purposes, that factor is very small, and once underwater, would not vary.

The laminar flow element (LFE)* produces a pressure differential proportional to flow rate. The LFE contains a metering section subdivided into many passages, each of small enough diameter to assure fully developed laminar flow. Because the pressure drop in laminar duct flow is directly proportional to flow rate, the pressure drop vs. flow rate relationship is linear. The LFE may be used with reasonable accuracy over a 10:1 flow rate range. Because the relationship between pressure drop and flow rate for laminar flow depends on viscosity, which is a strong function of temperature, fluid temperature must be known in order to obtain accurate metering.

An LFE costs approximately as much as a venturi, but is much lighter and smaller. Thus, the LFE is widely used in applications where compactness and extended range are important.

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"I don't know the percentage of the Internet that's valid, do you? Jesus, it's scary." - Hunter S. Thompson

enkelkijken

can you tell me where to find the section on laminair flow in the mentioned article??
are you looking into incompressible or compressible flows?
as fas as i can understand, we talk here about constant volume flow, and not constant mass flow
constant volume flow equals constant mass flow for noncompressible flow (like liquids), but does not work that way for gasses

paul

Dave Sutton

Another secret weapon discovered. We've been playing with one of these for the last six months and it does exactly what you think it does.
All theory held aside, chamber runs to 500 feet verify the results.

This *is* the holy grail of mCCR's for deep diving, and is the deluxe way to go about it. The part is of aerospace quality and is first rate.



Dave

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"Changes in Lattitudes, Changes in Attitudes, Nothing remains quite the same".... www.nobubblediving.com

Gill Envy

Oh, now you've done it Teksimple, the whole house of cards is comming down! Just when i've come round to the "MFO" camp, you have to throw this into the mix...and it turns out that Dave's been playing with this in his little shop of horrors for a while now and not telling us! WTF, it's just never a dull moment around here and it goes to show that just when you think you have it all figured out, THINK AGAIN, AND AGAIN, AND AGAIN.

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Gill Envy

...Because I wasn't born with gills!
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