SMI Scrubber

silent running

I forgot about the vacuum inbetween, great idea. I guess there's not much chance of putting that idea to work in a CCR though. Funny about your blanket being 2 sided, maybe it's a newer generation and has the metalic material inside. I don't have mine anymore, but it came with directions about which side to put towords you.

But doesn't it make sense that if you wanted to reflect heat back at it's source, a shiny surface would work best? Tinfoil has a shiny side and a dull one for just this reason, and I'd guess that the shiny inside of the thermos liner works the same way... -Andy

jradomski

except the space blankets are mostly "reflecting" radient heat.. Its really not a heat sink/source..

Its working on a different concept..

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mverick

What you are describing here has absolutely nothing to do with Thermal Mass. Which is what I was talking about.

You're talking about reflecting energy back. I'm talking about conducting energy back. From the Metal to the sorb. Which is a solid to a solid. Which is way efficient.

Laser light reflected from a shiny plate. Has nothing to do with what I'm talking about. Lasers are producing Light energy. You're sorb isn't lighting up.

Inner core of my Thermos is not shiny. And it works very well. Shiny is also easy to CLEAN. Nothing to stick or bond or grow into. That's why some went to shiny.

You don't seem to be getting there is more then one way to transfer energy. It isn't Reflected energy. Metal plate will absorb energy. Through the air passing by it and the heat passing through the solid sorb itself. It will then release energy from the plate to the air when the temp drops below the temp of the plate. Guess what. As long as the temp in the loop doesn't drop, neither will the heat in the plate. So you loose nothing there. If your surrounding air is 85f everything will come up to that temp. And stay till the surrounding air drops.

Now, the scrubber sorb is hotter. When it transfers heat to the plate it can actually hold the heat. It will release some to the air towards the bucket. Very small amount. But, it will conduct heat back to the sorb if it needs it. Quickly through conduction. From the metal plate to the sorb material. Solid to a solid.

And about releasing info. I never thought he would get on here and release info. I don't care what they release. From one machine to another. Specs will be different. That, is why no one releases info. One scuba compressor to another has different CFM's. And they all are rated differently. Why would I ever think this would be different.

All I want to hear is why Plastic is better then metal for the exterior plate of the Scrubber. He stated it was better. The analogy they used as a radiator is wrong. If that's his reason. He's wrong.

He tested a lot of things. Great. He also has a diminishing return to look at. One is, Military didn't want machined parts. Had to have injection molding. Injection molding of a plastic scrubber is way easier then of a Metal outside plated scrubber. So from the Cost/Benefit aspect. Plastic is the way to go. And, if the Military say's no to the machine work and you're trying to sell to that market. You're done right there. No matter what benefit the Metal plate may have had.

But that doesn't mean the Metal plated scrubber he tested didn't produce better results.

mverick

Oh,
Just a thought,

On a scrubber plate
You have radiant energy going back into the scrubber.
You have conduction energy going back into the scrubber.
You have convection energy going through the scrubber through airflow through the sorb out of the scrubber..
You have convection energy going through the scrubber back into the sorb at stagnant times.

Throw in the airflow throught the scrubber.
And the time the scrubber is stagnant.

Plus a couple other variables.

And you have Thermodynamics.

Add all your energy's to find out which way the energy will flow from the plate. Towards the bucket? Or towards the sorb? Also, know the efficiencys of the materials and the thermal mass of them to knock out variables.

Radiant is the least, Convection is behind it, with conduction being the greatest.

decoweenie

How many days and posts have you guys been "debating" this now ?

I am sure the horse is pretty tender by now...

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silent running

mverick, you've heard why plastic is better than metal-it conducts heat away from the source slower than metal does-it's a better barrier. If it works better for the outside-solid to liquid-why wouldn't it work best for the inside?

You say I don't know/care enough about heat transfer from solid to solid, even though the inside of a scrubber is far from solid. Remember that the sorb grains next to the metal scrubber are only at peak temp when they are reacting. This only occurs at the begining and hopefully not at the end... Other than the reaction front itself, the rest of the time it's the gas that's at the highest temp. Gas is much less dense than a solid and loses heat faster, especially when it comes in contact with cold metal. If people use metal in radiators to disapate heat, that means that metal does this fast/well and then the reverse would likely not be true.

I say that whatever holds heat loses it to the denser medium and that you don't take into account the huge thermal capacity of seawater to suck away heat from the air/scrubber. So where are we?

I have responded to several people, so that's why I don't answer every thing you say tit for tat. Sorry if my attention is divided, it's not an insult, I'm trying to think about all the posibilities. -Andy

silent running

Hey! I resemble that remark...

Louby Lou

Hi Folks

Just to let you know that Pete and Shas have updated the article on the SMI scrubber and there are some additional images as well.

The updated article can be found in the Rebreatherworld library HERE

Cheers again

Lou

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silent running

Good stuff, thanks very much for posting it Pete. So the first image is an in-out flow radial with composite/plastic scrubber and urethane bucket, the second image is in-out flow with SS 316 perforated scrubber and aly bucket and the third is of an out-in flow with those same metal materials.

According to the model, the metal components are clearly worse at slowing the heat loss to the 10C water, with the out-in flow metal component design being the worst of all. While it is only a simulation run on a computer, the differences in outlet temp btw the plastic components and the metal ones seem significant enough to make clear the poor insulating qualities of metal.

Pete, is the composite scrubber modeled with the same kind of nylon mesh as the Prism?