SMI Scrubber

silent running

Steve, unlike the metal in a ss perf scrubber, the space blanket is a directional device. With the aluminized side facing at a heat source, it will help keep heat in. And having used one in an old, cold, drafty house in my native St. Louis, they are not all that. They work great in space, where there is no wind to take away radiated heat, and work OK on earth when combined with another layer.

If the Meg scrubber, or the Cis had a layer of plastic laminated to the outside of perf ss in the same pattern, you might get a similar result. But btw the mesh, perf ss and then plastic it'd be on the thick side, probably better off with the extra layer of sorb you'd loose.... -Andy

silent running

Paul, I don't undersdtand. Are you saying the material of the scrubber itself-metal or plastic-doesn't matter at all? The Meg users think that a metal scrubber with mesh will hold heat better than a plastic frame with mesh. I say you can't have it both ways, something that holds heat also radiates it, especially into something cooler next to it.

On the inhale part of the cycle, there is very little movement of gas on the exhaled side of the loop. So on the Meg the gas would now be sitting for a few seconds next to the metal housing/plenum/bucket/can which is next to cold, dense seawater. How can there not be some transfer of heat from a warm metal scrubber to the colder, still gas sitting next to the even colder metal can, next to cold, dense seawater? -Andy

paulraymaekers

andy,

I suppose you're talking about a in-to-out configuration (altough inverse would be the same)

what I'm saying is that the isolation of the housing is 100 times more important than wether or not the cannister itself is made out of metal mesh/perforated plate or plastic

if the gas does not move at all between the outer housing and the scrubber mesh (witch is theory, gas always moves), in that case the heat-capacity of the metal mesh plays a role, but I doubth strongly that during those 2/3 seconds there is enough gas mouvement from outer housing to mesh to give mesurable temperature decrease.

radiation from mesh to housing is neglectable compared to heat-loss by conduction

regards
paul

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

RebreatherDave

I read the Tennessee move update.....was waiting for the CNC operator to use a compressed airgun to blow off the plastic chips so I could see the cutter path better....but I just had to think, rather then hiring an IT guy to remove all those viruses as stated, why not just get a Mac, whose users don't write viruses for their own OS....I mean, even dogs are smart enough not to take a dump where they sleep....

RonMicjan

huh??

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mverick

Plastic holds heat, Metal holds heat, Chewing gum holds heat. And, to be honest. It isn't holding heat. It's holding energy. But, it's already confusing enough. So, I ain't going there....

If there was enough plastic in the Prism scrubber to equal what the Metal scrubber can hold in heat. And, it could transfer the heat back to the Scubber material, Sorb, they would both have close to the same efficiency. Since the Plastic in the Prism Scrubber won't hold the same amount of heat. And, since it is a good insulator, it won't transfer the heat back to the Sorb as efficiently as Metal would.

I'm talking the material of the scrubber. Not the material in the scrubber.

I read Pete/Sharons post. Radiators have Big fans. Also, run higher speeds to pass all that air over that radiator. Huge surface area's because of fins and tubes. Multiple cores and small paths to transfer the heat to the metal. If you're trying to compare that to the metal in a scrubber. You're way off base. No way are they comparable. The surface area's of radiators are HUGE. The surface area of the metal scrubber isn't.

hyrax

Ok, I've been reading all your post. I think maybe you are missing something, yes the megs metal scrubber will hold heat, lots of it. The thing is the metal gets that heat from the scruber, thus dropping the temp of the scrubber. Then the water absorbs the heat from the metal. The plastic scrubber absorbs less heat and therefor insulates the scrubber from the water. Just as a thought try wrapping your Meg scrubber with Neoprene, I bet it will work better. Realy I couldn't tell you if one is better then the other, I don't own either one. Would love to own either one and for me it might come down to price.

silent running

mverick, now maybe it's me who's not being understood. You seem to be taking for granted that the metal of the Meg scrubber is ONLY transfering heat back-holding it in-to the sorb. Even Paul agrees that the energy/heat holding properties of metal are not a one way proposition. Remember, the differential in cold water btw the scrubber material and the outside water temp is significant-40F+degrees. And far more importantly, it's gas to metal to gas to seawater, which is far more dense than any gas and has a far greater capacity to absorb energy/heat.

You're right, the radiator comparison is not a great one, but not for the rerason you think-it's backward. With the metal scrubber to seawater chain you are not trying to disapate heat, you're trying to keep it in. And you're trying to keep it in a much less dense medium-gas-than the nearby colder medium which is much more dense-seawater. The medium which has the greater density/capacity to absorb the heat/energy will always win, so the best you can do is to slow it down as much as you can. 75F air feels warm to most people. 75F seawater does not. An OC diver without exposure protection will be very cold after 15 minutes, as they breathe and radiate away their body heat into the cool, dense seawater. Even with a good wet suit, most won't last 2 hours without losing a lot of heat and discomfort, our scrubbbers need to work efficiently for a lot longer than that.

Keeping things warm can only be done by insulating and slowing down the transfer of heat, not by absorbing heat. Metal is clearly not an insulator... -Andy

RonMicjan

Not quite correct sir

the scrubber reaction is exothermic, its making heat, so the stainless perfed surround is absorbing some of that and coming up to temp, the scrubber material is not becoming cooler during this process. The water does not touch the scrubber, anywhere, so there is no transfer there. You cannot wrap a radial scrubber in neoprene, this would block all gas flow.

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hyrax

Ahh, yes not really what I meant. I think maybe part of the problem here is sometimes we think we are talking about the same part and we are not. My fault completely, I don't mean the scrubber but rather the scrubber housing? So in the case of the meg the metal housing would pull heat from the gas going into the scrubber. I would think the warmer the gas going into the scrubber the better the reaction. When you get right down to it sure the scrubber being made of metal doesn't mater much either way. But what about the housing?