SMI Scrubber

mverick · 25th August 2006, 02:51

Quote: (Originally Posted by silent running)

mverick, I think the problem with this analysis is that the very thing you think is an advantage-metal heat conductivity-is actually a disadvantage when you are trying to slow down the transmission of heat from say a 100F loop to 65F water. You want a barrier material between the water and gas with less heat conductivity + an air insulator. Plastic has much less=slower heat conductivity than metal. If you were to put a Prism scrubber bucket in the fire it would probaly start to melt before it burned you. I'm reasonably sure a Meg plenum put to the same fire would heat up rapidly and burn you good in short order.

In a radial design, air would be the best insulator btw the scrubber and the bucket and plastic the lowest heat conducting actual solid barrier btw the 2 temp extremes. -Andy

No matter what you loose heat. When the air comes through the scrubber. It hits the Bucket. Bam you loose heat. And, you condense your water.

Not saying this is true. But just for a thinking point.

Air Temp coming through the scrubber is 120. Hits the Bucket and down to 90. So, the Temp of the metal is 120. Same temp of plastic. The temp of the metal got to 120 early in the process. Not late. So, it holds the heat you put into it. It might loose 2 degrees to the air. But, it will transfer that 120 heat back to the scrubber if needed. Much, Much easier than to the air. The benefit out weighs the detriment.

The Metal will actually help keep the Scrubber temp up. It holds some of the heat you would loose from the air through the scrubber hitting the bucket.

Take the loaded scrubber. Put it in an oven. Heat it till it's 250. Now, put in a box and see which scrubber will hold temp longer. The one with more thermal mass will. Which is the one with the metal.

The metal helps hold the heat you loose from the air hitting the bucket. More heat will radiate back into the scrubber bed you would have lost from it hitting the sides of the bucket. So, you loose less heat to the surrounding water. It's saved in the metal. You're already dumping a lot of heat into the water no mater what. So, if you dump less heat to the water and hold it in the steel. Where is the bad in that? You're not robbing heat from the scrubber. It's heat that was going to the water anyway. And, it can go back into the scrubber bed if temps drop.

With the steel, your not robbing the heat from the scrubber itself. Your robbing heat from the air that was going to hit the bucket walls to condense your water.

From what I understand. Plastic was also because of Military requirements of it being a molded and not machined unit. That was why most things were molded from what everyone has said.

After re reading this. Not quite as thorough as I'd like. But, I'm bushed. So going to bed. Going to Ozarks for the boat races tomorrow.

mverick · 25th August 2006, 02:54

Quote: (Originally Posted by silent running)

Also mverick, the Prism is very unlikely to flood through the center tube for the reasons I mentioned on the Meg radial thread. I think the chance is next to nil. And I don't think there's any bashing going on, just people hashing things out... -Andy

Murphy has a different opinion.

He's right a lot so I trust him.... LOL

***jradomski*** · 25th August 2006, 03:08

Quote: (Originally Posted by silent running)

mverick, I think the problem with this analysis is that the very thing you think is an advantage-metal heat conductivity-is actually a disadvantage when you are trying to slow down the transmission of heat from say a 100F loop to 65F water. You want a barrier material between the water and gas with less heat conductivity + an air insulator. Plastic has much less=slower heat conductivity than metal. If you were to put a Prism scrubber bucket in the fire it would probaly start to melt before it burned you. I'm reasonably sure a Meg plenum put to the same fire would heat up rapidly and burn you good in short order.

In a radial design, air would be the best insulator btw the scrubber and the bucket and plastic the lowest heat conducting actual solid barrier btw the 2 temp extremes. -Andy

Andy I don't thinkyou see mavs point..

Metal on the scrubber is good, metal on the bucket (as you prism people call it) is a different issue..

The water interface in metal would be worse than plastic.. but there is an air gap interface which is an insulator to the scrubber.. the metal on the scrubber retains heat for the scrubber and can give some back..

A plastic bucket and metal scrubber would be superior to plastic/plastic..

metal bucket would lose alot of heat in an out to in situation, would have to see really how bad it was on an in to out.. It would probably condense alot of the loop moisture though.

silent running · 25th August 2006, 03:21

Quote: (Originally Posted by mverick)

No matter what you loose heat. When the air comes through the scrubber. It hits the Bucket. Bam you loose heat. And, you condense your water.

Not saying this is true. But just for a thinking point.

Air Temp coming through the scrubber is 120. Hits the Bucket and down to 90. So, the Temp of the metal is 120. Same temp of plastic. The temp of the metal got to 120 early in the process. Not late. So, it holds the heat you put into it.

Not if the much denser water surrounding that bucket is already 65F. That 120F air is going to be cooled a lot if it hits a 65F scrubber bucket. Remember, metal conducts cold too.-Andy

Steve · 25th August 2006, 03:27

Quote: (Originally Posted by silent running)

mverick, I think the problem with this analysis is that the very thing you think is an advantage-metal heat conductivity-is actually a disadvantage when you are trying to slow down the transmission of heat from say a 100F loop to 65F water. You want a barrier material between the water and gas with less heat conductivity + an air insulator. Plastic has much less=slower heat conductivity than metal. If you were to put a Prism scrubber bucket in the fire it would probaly start to melt before it burned you. I'm reasonably sure a Meg plenum put to the same fire would heat up rapidly and burn you good in short order.

In a radial design, air would be the best insulator btw the scrubber and the bucket and plastic the lowest heat conducting actual solid barrier btw the 2 temp extremes. -Andy

Andy,
First up, what are you referring to as the plenum?

And secondly you have hit the nail on the heat with your last sentence. The constantly moving mass of air between the scrubber and its housing (can) negates a good chunk of the issue of the thermal conductivity of the can. Not all of it though. From a thermal conductivity point of view a plastic would be better than a metal to construct a can but from a lets go diving point of view the tougher metal is better. I’m yet to see a broken metal can but have seen a few broken plastic ones.

The scrubber is an easy one to test. I will have a mate take the Meg axial, the Meg radial and the Prism scrubber and go diving. The loop temperature will reveal all. My money is on the metal radial as being the most thermally efficient.

Did Pete ever supply the information for testing the scrubber on the Prism in both directions? That would be very interesting data to look at.

mverick · 25th August 2006, 03:27

Quote: (Originally Posted by silent running)

Not if the much denser water surrounding that bucket is already 65F. That 120F air is going to be cooled a lot if it hits a 65F scrubber bucket. Remember, metal conducts cold too.-Andy

What metal? The prism bucket is a Plastic... And transfer of heat from the 65F bucket to the 120 air isn't going to knock the temps down to 65F. It might drop them 30F but, that's a lot of drop. Air to a plastic.

I'm talking about the prism. I want to make that clear.

silent running · 25th August 2006, 03:49

Quote: (Originally Posted by jradomski)

Andy I don't thinkyou see mavs point..

Metal on the scrubber is good, metal on the bucket (as you prism people call it) is a different issue..

The water interface in metal would be worse than plastic.. but there is an air gap interface which is an insulator to the scrubber.. the metal on the scrubber retains heat for the scrubber and can give some back..

A plastic bucket and metal scrubber would be superior to plastic/plastic..

metal bucket would lose alot of heat in an out to in situation, would have to see really how bad it was on an in to out.. It would probably condense alot of the loop moisture though.

Hi Joe, thanks for clearing that up, if that's what he meant, then maybe it's worth considering. But he just keeps mentioning the air hitting the bucket, so I was trying to address that first. As for a metal scrubber it might "give something back" but remember it's still in contact with the cooler outside jacket air and radiating out into it. At a certain point even a radiator won't do much to heat the surrounding air in a room that's 40 degrees colder than it is, especially if that air is constantly being exchanged and has to pass next to another surface that's much cooler, like a window.

Also it would be made of perforated stuff, like the Meg, right? Then it has many perforations, this as opposed to a fine mesh like the Prism. If we add it up then I'd bet there's more flow through area with the mesh than perforated and a more uniform flow=more efficeincy, less chance of channeling and probably better WOB. So I'd be doubtful that whatever the perf metal gave back would be worth the flow trade off. Also, isn't the Boris scrubber outlet also perforated and said to need the porex membrane just to deal with the dusting/cocktail that comes from the larger stuff falling through? -Andy

silent running · 25th August 2006, 03:55

Quote: (Originally Posted by mverick)

What metal? The prism bucket is a Plastic... And transfer of heat from the 65F bucket to the 120 air isn't going to knock the temps down to 65F. It might drop them 30F but, that's a lot of drop. Air to a plastic.

I'm talking about the prism. I want to make that clear.

Sorry mverick, I think I understand you now. The repetition of the word "bucket" has got to me, making me regress to a more primal, hill-billy like state... -Andy

silent running · 25th August 2006, 04:09

Quote: (Originally Posted by Steve)

Andy,
First up, what are you referring to as the plenum?

And secondly you have hit the nail on the heat with your last sentence. The constantly moving mass of air between the scrubber and its housing (can) negates a good chunk of the issue of the thermal conductivity of the can. Not all of it though. From a thermal conductivity point of view a plastic would be better than a metal to construct a can but from a lets go diving point of view the tougher metal is better. I’m yet to see a broken metal can but have seen a few broken plastic ones.

The scrubber is an easy one to test. I will have a mate take the Meg axial, the Meg radial and the Prism scrubber and go diving. The loop temperature will reveal all. My money is on the metal radial as being the most thermally efficient.

Did Pete ever supply the information for testing the scrubber on the Prism in both directions? That would be very interesting data to look at.

Howdy Steve, I was told by Killer Ron that you Megalithic peoples refer to the scrubber housing/can as the "plenum", whilst we Prismatics refer to the in and out gas spaces in the head as the "plenum".
How will you test the temps on the Prism, after the dive? There's no temp monitor in the loop...

If you read the SMI scrubber article, there's a bit about how testing at 65F with a reverse out to in flow on the Prism saw a notable decrease in scubber efficeincy/duration. This would be even more drastic with a metal can/plenum/bucket. Not more detail than that, but if you ask him a specific question, I'm sure he will answer it eventually. -Andy

***jradomski*** · 25th August 2006, 04:36

Quote: (Originally Posted by silent running)

Hi Joe, thanks for clearing that up, if that's what he meant, then maybe it's worth considering. But he just keeps mentioning the air hitting the bucket, so I was trying to address that first. As for a metal scrubber it might "give something back" but remember it's still in contact with the cooler outside jacket air and radiating out into it. At a certain point even a radiator won't do much to heat the surrounding air in a room that's 40 degrees colder than it is, especially if that air is constantly being exchanged and has to pass next to another surface that's much cooler, like a window.

Also it would be made of perforated stuff, like the Meg, right? Then it has many perforations, this as opposed to a fine mesh like the Prism. If we add it up then I'd bet there's more flow through area with the mesh than perforated and a more uniform flow=more efficeincy, less chance of channeling and probably better WOB. So I'd be doubtful that whatever the perf metal gave back would be worth the flow trade off. Also, isn't the Boris scrubber outlet also perforated and said to need the porex membrane just to deal with the dusting/cocktail that comes from the larger stuff falling through? -Andy

The CIS scrubber and those modeled after it have a perferated outer ss layer, for protection and two inner SS screens (outer area and center tube)to hold the sorb in place..

You can partially see it in the attached pic

25th August 2006, 02:51	#21 (permalink)
mverick ScubaPimp Current Rebreather/s: Megalodon Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Aug 2005 Posts: 577	Re: SMI Scrubber Quote: (Originally Posted by silent running) mverick, I think the problem with this analysis is that the very thing you think is an advantage-metal heat conductivity-is actually a disadvantage when you are trying to slow down the transmission of heat from say a 100F loop to 65F water. You want a barrier material between the water and gas with less heat conductivity + an air insulator. Plastic has much less=slower heat conductivity than metal. If you were to put a Prism scrubber bucket in the fire it would probaly start to melt before it burned you. I'm reasonably sure a Meg plenum put to the same fire would heat up rapidly and burn you good in short order. In a radial design, air would be the best insulator btw the scrubber and the bucket and plastic the lowest heat conducting actual solid barrier btw the 2 temp extremes. -Andy No matter what you loose heat. When the air comes through the scrubber. It hits the Bucket. Bam you loose heat. And, you condense your water. Not saying this is true. But just for a thinking point. Air Temp coming through the scrubber is 120. Hits the Bucket and down to 90. So, the Temp of the metal is 120. Same temp of plastic. The temp of the metal got to 120 early in the process. Not late. So, it holds the heat you put into it. It might loose 2 degrees to the air. But, it will transfer that 120 heat back to the scrubber if needed. Much, Much easier than to the air. The benefit out weighs the detriment. The Metal will actually help keep the Scrubber temp up. It holds some of the heat you would loose from the air through the scrubber hitting the bucket. Take the loaded scrubber. Put it in an oven. Heat it till it's 250. Now, put in a box and see which scrubber will hold temp longer. The one with more thermal mass will. Which is the one with the metal. The metal helps hold the heat you loose from the air hitting the bucket. More heat will radiate back into the scrubber bed you would have lost from it hitting the sides of the bucket. So, you loose less heat to the surrounding water. It's saved in the metal. You're already dumping a lot of heat into the water no mater what. So, if you dump less heat to the water and hold it in the steel. Where is the bad in that? You're not robbing heat from the scrubber. It's heat that was going to the water anyway. And, it can go back into the scrubber bed if temps drop. With the steel, your not robbing the heat from the scrubber itself. Your robbing heat from the air that was going to hit the bucket walls to condense your water. From what I understand. Plastic was also because of Military requirements of it being a molded and not machined unit. That was why most things were molded from what everyone has said. After re reading this. Not quite as thorough as I'd like. But, I'm bushed. So going to bed. Going to Ozarks for the boat races tomorrow. Last edited by mverick : 25th August 2006 at 03:08.
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25th August 2006, 02:54	#22 (permalink)
mverick ScubaPimp Current Rebreather/s: Megalodon Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Aug 2005 Posts: 577	Re: SMI Scrubber Quote: (Originally Posted by silent running) Also mverick, the Prism is very unlikely to flood through the center tube for the reasons I mentioned on the Meg radial thread. I think the chance is next to nil. And I don't think there's any bashing going on, just people hashing things out... -Andy Murphy has a different opinion. He's right a lot so I trust him.... LOL
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25th August 2006, 03:08	#23 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,133	Re: SMI Scrubber Quote: (Originally Posted by silent running) mverick, I think the problem with this analysis is that the very thing you think is an advantage-metal heat conductivity-is actually a disadvantage when you are trying to slow down the transmission of heat from say a 100F loop to 65F water. You want a barrier material between the water and gas with less heat conductivity + an air insulator. Plastic has much less=slower heat conductivity than metal. If you were to put a Prism scrubber bucket in the fire it would probaly start to melt before it burned you. I'm reasonably sure a Meg plenum put to the same fire would heat up rapidly and burn you good in short order. In a radial design, air would be the best insulator btw the scrubber and the bucket and plastic the lowest heat conducting actual solid barrier btw the 2 temp extremes. -Andy Andy I don't thinkyou see mavs point.. Metal on the scrubber is good, metal on the bucket (as you prism people call it) is a different issue.. The water interface in metal would be worse than plastic.. but there is an air gap interface which is an insulator to the scrubber.. the metal on the scrubber retains heat for the scrubber and can give some back.. A plastic bucket and metal scrubber would be superior to plastic/plastic.. metal bucket would lose alot of heat in an out to in situation, would have to see really how bad it was on an in to out.. It would probably condense alot of the loop moisture though. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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25th August 2006, 03:21	#24 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,881	Re: SMI Scrubber Quote: (Originally Posted by mverick) No matter what you loose heat. When the air comes through the scrubber. It hits the Bucket. Bam you loose heat. And, you condense your water. Not saying this is true. But just for a thinking point. Air Temp coming through the scrubber is 120. Hits the Bucket and down to 90. So, the Temp of the metal is 120. Same temp of plastic. The temp of the metal got to 120 early in the process. Not late. So, it holds the heat you put into it. Not if the much denser water surrounding that bucket is already 65F. That 120F air is going to be cooled a lot if it hits a 65F scrubber bucket. Remember, metal conducts cold too.-Andy
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25th August 2006, 03:27	#25 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,135	Re: SMI Scrubber Quote: (Originally Posted by silent running) mverick, I think the problem with this analysis is that the very thing you think is an advantage-metal heat conductivity-is actually a disadvantage when you are trying to slow down the transmission of heat from say a 100F loop to 65F water. You want a barrier material between the water and gas with less heat conductivity + an air insulator. Plastic has much less=slower heat conductivity than metal. If you were to put a Prism scrubber bucket in the fire it would probaly start to melt before it burned you. I'm reasonably sure a Meg plenum put to the same fire would heat up rapidly and burn you good in short order. In a radial design, air would be the best insulator btw the scrubber and the bucket and plastic the lowest heat conducting actual solid barrier btw the 2 temp extremes. -Andy Andy, First up, what are you referring to as the plenum? And secondly you have hit the nail on the heat with your last sentence. The constantly moving mass of air between the scrubber and its housing (can) negates a good chunk of the issue of the thermal conductivity of the can. Not all of it though. From a thermal conductivity point of view a plastic would be better than a metal to construct a can but from a lets go diving point of view the tougher metal is better. I’m yet to see a broken metal can but have seen a few broken plastic ones. The scrubber is an easy one to test. I will have a mate take the Meg axial, the Meg radial and the Prism scrubber and go diving. The loop temperature will reveal all. My money is on the metal radial as being the most thermally efficient. Did Pete ever supply the information for testing the scrubber on the Prism in both directions? That would be very interesting data to look at. __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
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25th August 2006, 03:27	#26 (permalink)
mverick ScubaPimp Current Rebreather/s: Megalodon Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Aug 2005 Posts: 577	Re: SMI Scrubber Quote: (Originally Posted by silent running) Not if the much denser water surrounding that bucket is already 65F. That 120F air is going to be cooled a lot if it hits a 65F scrubber bucket. Remember, metal conducts cold too.-Andy What metal? The prism bucket is a Plastic... And transfer of heat from the 65F bucket to the 120 air isn't going to knock the temps down to 65F. It might drop them 30F but, that's a lot of drop. Air to a plastic. I'm talking about the prism. I want to make that clear.
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25th August 2006, 03:49	#27 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,881	Re: SMI Scrubber Quote: (Originally Posted by jradomski) Andy I don't thinkyou see mavs point.. Metal on the scrubber is good, metal on the bucket (as you prism people call it) is a different issue.. The water interface in metal would be worse than plastic.. but there is an air gap interface which is an insulator to the scrubber.. the metal on the scrubber retains heat for the scrubber and can give some back.. A plastic bucket and metal scrubber would be superior to plastic/plastic.. metal bucket would lose alot of heat in an out to in situation, would have to see really how bad it was on an in to out.. It would probably condense alot of the loop moisture though. Hi Joe, thanks for clearing that up, if that's what he meant, then maybe it's worth considering. But he just keeps mentioning the air hitting the bucket, so I was trying to address that first. As for a metal scrubber it might "give something back" but remember it's still in contact with the cooler outside jacket air and radiating out into it. At a certain point even a radiator won't do much to heat the surrounding air in a room that's 40 degrees colder than it is, especially if that air is constantly being exchanged and has to pass next to another surface that's much cooler, like a window. Also it would be made of perforated stuff, like the Meg, right? Then it has many perforations, this as opposed to a fine mesh like the Prism. If we add it up then I'd bet there's more flow through area with the mesh than perforated and a more uniform flow=more efficeincy, less chance of channeling and probably better WOB. So I'd be doubtful that whatever the perf metal gave back would be worth the flow trade off. Also, isn't the Boris scrubber outlet also perforated and said to need the porex membrane just to deal with the dusting/cocktail that comes from the larger stuff falling through? -Andy
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25th August 2006, 03:55	#28 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,881	Re: SMI Scrubber Quote: (Originally Posted by mverick) What metal? The prism bucket is a Plastic... And transfer of heat from the 65F bucket to the 120 air isn't going to knock the temps down to 65F. It might drop them 30F but, that's a lot of drop. Air to a plastic. I'm talking about the prism. I want to make that clear. Sorry mverick, I think I understand you now. The repetition of the word "bucket" has got to me, making me regress to a more primal, hill-billy like state... -Andy
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25th August 2006, 04:09	#29 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,881	Re: SMI Scrubber Quote: (Originally Posted by Steve) Andy, First up, what are you referring to as the plenum? And secondly you have hit the nail on the heat with your last sentence. The constantly moving mass of air between the scrubber and its housing (can) negates a good chunk of the issue of the thermal conductivity of the can. Not all of it though. From a thermal conductivity point of view a plastic would be better than a metal to construct a can but from a lets go diving point of view the tougher metal is better. I’m yet to see a broken metal can but have seen a few broken plastic ones. The scrubber is an easy one to test. I will have a mate take the Meg axial, the Meg radial and the Prism scrubber and go diving. The loop temperature will reveal all. My money is on the metal radial as being the most thermally efficient. Did Pete ever supply the information for testing the scrubber on the Prism in both directions? That would be very interesting data to look at. Howdy Steve, I was told by Killer Ron that you Megalithic peoples refer to the scrubber housing/can as the "plenum", whilst we Prismatics refer to the in and out gas spaces in the head as the "plenum". How will you test the temps on the Prism, after the dive? There's no temp monitor in the loop... If you read the SMI scrubber article, there's a bit about how testing at 65F with a reverse out to in flow on the Prism saw a notable decrease in scubber efficeincy/duration. This would be even more drastic with a metal can/plenum/bucket. Not more detail than that, but if you ask him a specific question, I'm sure he will answer it eventually. -Andy
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