Sciencemadness Discussion Board

Dry ice nozzles

peach - 3-8-2010 at 14:19

I'm starting to need some dry ice, but buying it means buying big bags or blocks and it's very expensive (I have used the yellow pages and called around, no one locally will do a small bagful or do it cheaply).

So I need to make my own really.

I know how the process works, and I've seen the dry ice nozzles for siphon cylinders.

But I'm somewhat put off by the prices. They're either around £100 or more in the UK.

From what I understand, they're essentially just a plastic tube or funnel with a shower head like perforated plate inside. I've seen one on the US eGay that someone has obviously made at home, as it's a length of plastic plumbing pipe. I'm not really willing to spend $70 - 80 plus the shipping, import duty and tax for what amounts to a pound or twos worth of pipe fittings.

I already have a fancy CO2 take off designed for use with paintball markers. These use liquid CO2 in their tanks to shoot the bruise inducing painballs out. The take off has a lever valve to open the flow to the tank, another to purge it, a connection point for the purge to go out through and a needle pin to open the markers tank. This latter bit is connected via a flexible, steel braid lined hose as well.

If anything, my painintheass marker takeoff is overqualified for the job. Dry ice build up is actually a problem for paintball marker filling when playing, as so many people will be filling the tanks up there'll be dry icicles hanging off the exhaust of the takeoff.

All I need do is couple the hose to a suitable nozzle.

Is the nozzle really as simple as an open funnel or tube? Or do they have a little 'shower head' at the top to produce flakes?

I'll be sticking a cloth bag over the end to catch it all and encourage build up as opposed to escape.

I am very used to working with oxy/acetylene, propane, MAPP, air and inert gas cylinders, that's not a problem.

Shouldn't take me more than a few hours to get the bits and put a nozzle together for the takeoff. If someone can provide some more details, like a photo of the inside of the nozzle or a rough size for the holes and quantity, I'll post some piccy's of my DIY version up when done.

[Edited on 3-8-2010 by peach]

The WiZard is In - 3-8-2010 at 15:18

Quote: Originally posted by peach  
I'm starting to need some dry ice, but buying it means buying big bags or blocks and it's very expensive (I have used the yellow pages and called around, no one locally will do a small bagful or do it cheaply).



A- You need a CO2 cylinder with a siphon tube.
B- You can buy a device to attach to la cylinder for US $120 or so.
C- This is an v/ v/ expensive way to make dry ice


[Edited on 3-8-2010 by The WiZard is In]

peach - 3-8-2010 at 15:46

A- I have had a BOC account for over a decade, already have the takeoff for a syphon cylinder and realize I need these two elements. Hence me mentioning both.

B- I don't live in the US, and pointed out the shipping, duty and tax issues.

B.part2- I also pointed out why I didn't see fit to spend $120+ on what amounts to a piece of plumbing tube given that I already have the takeoff.

C- I also mentioned that the local suppliers will only do it in big bags or expensively. The cylinder companies want me to buy 10 - 15kg bags, when I'll use a kilo or so then have the rest sublime off in the weeks between needing it. The only people who'll do me a single block want something like £20 - 35 for a one kilo block.

C.part2- From my quick googling, a 50lb (~25kg) syphon cylinder will cost around $25 (I dunno, ?£18?) per fill. The nozzles will produce one kilo of dry ice per four kilos of CO2 that goes through. Meaning I can generate a kilo on demand for around £5-6.

I'm not trying to be a gimp (although I expect it will seem I am), but I did cover those in the original question.

Mr. Wizard - 4-8-2010 at 07:12

A search of images on the web > dry ice maker < reveals the apparatus you need to be nothing more than a nozzle that dumps liquid CO2 into a chamber to form the dry ice block. The chamber has to be constructed of a material that will allow the gaseous CO2 to escape while retaining the dry ice snow that forms. One method was just to allow the liquid to flow into a cloth bag. This doesn't give you a shaped block. Make a reinforced wooden box with plenty of strong porous cloth to vent the gas and save the 'snow'. One showed a picture of two disks with a Velcro attached cloth side.

You need to have a liquid flow out, so you must use a 'siphon tube' tank which has a tube running to the bottom of the CO2 tank under the liquid.

I don't know if inverting the tank to get liquid flowing out is the equivalent or not, but it seems reasonable. An inverted tank is a heavy unstable object, so if you plan to do this make some sort of stable tilting machine, don't just tip over a tank. Even the smaller tanks are very heavy when full, and the big ones almost take two people to move or lift.

CO2 has a critical temperature of 31C, so there will not be a gas / liquid phase in a tank at or over, this temperature. You will not get as efficient production of dry ice either, wasting much more gas.

The colder the initial CO2 in the tank, the more efficient the dry ice production. Pre-cooling the tank will increase the amount you will get from any tank.

Most CO2 tanks have their empty (tare) and full (net) weights stamped on the tank. This is how you determine how much gas is left, as the pressure doesn't change much while there is a liquid inside.

[Edited on 4-8-2010 by Mr. Wizard]

crazyboy - 4-8-2010 at 14:48

Quote: Originally posted by peach  

C.part2- From my quick googling, a 50lb (~25kg) syphon cylinder will cost around $25 (I dunno, ?£18?) per fill. The nozzles will produce one kilo of dry ice per four kilos of CO2 that goes through. Meaning I can generate a kilo on demand for around £5-6.


That's insane! Stores near my house sell dry ice for $1.50-2.50 a pound.


peach - 4-8-2010 at 16:13

Quote: Originally posted by crazyboy  

That's insane! Stores near my house sell dry ice for $1.50-2.50 a pound.


Yep, that's England. That's part of the reason why the pound is worth more than the dollar. The county is tiny, everyone wants to live in London (pretty much) and there are hundreds of thousands of people flooding into the place from abroad all the time. So there's no need to drive the prices down when there's a huge number of people willing to pay more than the next person to live here. With our free medical care, endless benefits and such, people will put up with the everyday prices to live here. America is fk'ing HUGE by comparison and (despite there being more people there) the density is no where near as high. A normal (for England) house here is $100 - 300k. There are numerous places in the US where I can buy a small mansion for that, with acres of garden and forests around me.

Places like London are also surrounded by 'green belt', which means no building tower blocks and such in them. And, in some cases, no building anything at all, or setting up mobile homes (countryside). I suppose these would be national parks in the US. So the size is severely limited by the bands of countryside around the areas, but the influx of people willing to part with money is massive.

I don't know what you mean by stores but, here, there are no normal stores you can go to to pick up dry ice. It's the cylinder companies or not a lot else.

Hence the nozzle requirement.

peach - 4-8-2010 at 16:25

@Wizard

Again, not wishing to be a gimp, but have you ever actually used a dry ice nozzle?

I've seen the pictures of the block formers, but I was asking about 'snow'.

You mention syphon cylinder, again, even though I've already mentioned them in the original post and again in the reply. I know what they are and have done for a decade +.

Then things like the safety of flipping a normal cylinder upside down, even though I've said I know what I'm doing with cylinders, know what a syphon cylinder is and that I've been using more dangerous cylinders for a decade or more.

I'm asking about the nozzles that spray the liquid CO2 down a tube and produce snow, not blocks or bulk solids. The snow suggests there's a perforated plate in the tube, which those images don't show. The dry ice 'guns' or 'nozzles', not block formers.

I know that spraying liquid CO2 through an enclosed space will produce a block; see my reply, again, about dry icicles hanging off the paintball marker takeoffs.

This is specifically about the nozzles that produce a bag full of snow, that can be easily poured into a dewar.

[Edited on 5-8-2010 by peach]

entropy51 - 4-8-2010 at 16:50

Quote: Originally posted by peach  
Quote: Originally posted by crazyboy  

That's insane! Stores near my house sell dry ice for $1.50-2.50 a pound.


Yep, that's England. That's part of the reason why the pound is worth more than the dollar. The county is tiny, everyone wants to live in London (pretty much) and there are hundreds of thousands of people flooding into the place from abroad all the time. So there's no need to drive the prices down when there's a huge number of people willing to pay more than the next person to live here. With our free medical care, endless benefits and such, people will put up with the everyday prices to live here. America is fk'ing HUGE by comparison and (despite there being more people there) the density is no where near as high. A normal (for England) house here is $100 - 300k. There are numerous places in the US where I can buy a small mansion for that, with acres of garden and forests around me.

Places like London are also surrounded by 'green belt', which means no building tower blocks and such in them. And, in some cases, no building anything at all, or setting up mobile homes (countryside). I suppose these would be national parks in the US. So the size is severely limited by the bands of countryside around the areas, but the influx of people willing to part with money is massive.

I don't know what you mean by stores but, here, there are no normal stores you can go to to pick up dry ice. It's the cylinder companies or not a lot else.

Hence the nozzle requirement.
This is very interesting social commentary, but fails to explain why you cannot find a vendor of dry ice. Where I live, $ 300,000 will only buy one a small shack in a bad neighborhood. You well describe the situation where I live, but lo and behold, there are several places at which one can buy dry ice.

I wouldn't have found these vendors either if I spent as much time composing long elaborate banal posts as you do.
Quote: Originally posted by peach  
Again, not wishing to be a gimp, but have you ever actually used a dry ice nozzle?


Despite your protestations to the contrary, you do very much appear a gimp. Whatever that is. Smacks of bigotry if you ask me.

[Edited on 5-8-2010 by entropy51]

[Edited on 5-8-2010 by entropy51]

Mr. Wizard - 4-8-2010 at 19:13

I've used a CO2 fire extinguisher into a pillow case with a six pack of beer in it. The dry ice snow was all over the bag and the beer was quite cold. Sorry about too many details. Good luck.

zed - 4-8-2010 at 21:20

You don't need a dry ice dealer. You need an ice cream dealer.

I knew a woman a few years ago, that sold ice-cream from a bicycle based ice-cream cart.

Without cheap dry ice, her small business couldn't have survived.

Perhaps you can befriend such a person.

At the end of her evening, when the ice cream was sold out, whatever dry ice remained, became dump-able surplus.

peach - 5-8-2010 at 03:35

Quote: Originally posted by entropy51  


This is very interesting social commentary, but fails to explain why you cannot find a vendor of dry ice. Where I live, $ 300,000 will only buy one a small shack in a bad neighborhood. You well describe the situation where I live, but lo and behold, there are several places at which one can buy dry ice.


I was very careful to include the phrase 'part of the reason' in the second sentence. And I was replying to crazyboy about the cost of the dry ice, not it's availability.

Quote:

I wouldn't have found these vendors either if I spent as much time composing long elaborate banal posts as you do.


Regardless of what I post, I can virtually guarantee I'll get some complaining. And then I have people PM'ing me to say thanks for posts. Not much I can do about that, so take it however you like; I can't write to please everyone.

And, I have not only searched through applegate and googled for local suppliers, but called the ones listed in the Yellow Pages. Failing that, I thought I'd consult a forum where I'd expect at least someone to have seen one in person.

Quote:
Despite your protestations to the contrary, you do very much appear a gimp. Whatever that is. Smacks of bigotry if you ask me.


I asked a very simple question at the start of the thread and made it clear why I was asking it.

Would you care to elaborate on how I'm being a bigot?

I can elaborate on an observation I've made, you seem intent on having a complain about pretty much whatever I say, regardless of whether or not people like DuPont agree with me.
Quote: Originally posted by Mr. Wizard  
I've used a CO2 fire extinguisher into a pillow case with a six pack of beer in it. The dry ice snow was all over the bag and the beer was quite cold. Sorry about too many details. Good luck.


Did you get snowy solid or was it packed on like icicles? Good application of the technology. I welcome the extra details if only for others who don't know to see, I just need the specific ones that I can't yet be sure of (e.g. perforated plate or not).
Quote: Originally posted by zed  
You don't need a dry ice dealer. You need an ice cream dealer.


:D

chief - 5-8-2010 at 11:58

Who really desperately needs it could try
==> to connect 2 refrigerator-compressors in series ...
==> and compress some CO2 into a reservoir within a deep-cooling fridge ...

At the -20 [Cels] that such a fridge can do (-35 with disabled temperature-regulation)
==> the liquefieing-pressure of the CO2 could be in range for the 2 fridge-compressors (in series) ...

So the CO2 could come from some burning of anything or wherefrom ever ...
==> Only that the N2 from the air might disturb the efficiency ...

not_important - 5-8-2010 at 12:51

They can get liquid CO2, burning shit means crappy CO2 that would possibly need to be dried, and again possibly further purified to preserve the compressors. The question is specific about the nozzle and other hardware needed to make dry ice, not how to make liquid CO2 from coal.

I've lived in places where no dry ice was easy to find, suppliers being many km distant. And I've lived places were not only dry ice was easy to get, but there were 3 sources of LN2 within 4 km. What's available varies from region to region, as does prices.

As suggested checking with frozen novelties reailers may lead to a lower cost source of dry ice. Building a stand to safely flip the tank may be cheaper than buying or even building a siphon tube. As for the nozzle, I've no experience there.

chief - 6-8-2010 at 08:08

The question was also about a somewhat feasible way to make the dry-ice ...
==> Have fun with the cops when they think you need the CO2 for some growth-boosted crops of some sort ... :o

Where there is no dry-ice there is probably no liquid CO2 either, and someone mentioned it to be a quite expensive way anyhow ...

Here the phase-diagram of CO2:
http://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-te...

Maybe the CO2 could just be converted without the step of liquefaction by compressing it, cooling it in the standard-frige to -35 [Cels] (eg. in copper-tubing)
==> and then expanding it through a standard refrigerator-nozzle ... :o


[Edited on 6-8-2010 by chief]

MagicJigPipe - 6-8-2010 at 09:49
Quote:

I don't know what you mean by stores


Grocery stores and some hardware stores carry dry ice in the U.S.

Also, most gas suppliers in most medium to large cities (100,000 + population) will supply LN2 to anyone with a DEWAR. This is based only on limited and anecdotal evidence, but it makes sense that what is the case in several cities, would be the case in the rest.
Quote:

Where I live, $ 300,000 will only buy one a small shack in a bad neighborhood.


Are you being pretentious? I assume you are because of your previous behavior (caustic personality). Calm down please.

Also, where do you live? It certainly can't be in the U.S. if anyone is to take your statement seriously. Maybe you could offer some proof...


[Edited on 8-6-2010 by MagicJigPipe]

anotheronebitesthedust - 6-8-2010 at 10:19

Quote:
Where I live, $ 300,000 will only buy one a small shack in a bad neighborhood.

The sad truth is that this is becoming more and more common in countries that heven't hit a recession yet. Nature has a way of leveling out the playing field. Old money can only buy so many new homes to rent to the young before the young want a place of their own. But I guess that's the circle of life.

peach - 6-8-2010 at 13:58

@not_important & cheif

I think both of you are making fairly valid points. not_important is correct that I would prefer just the simplicity of the nozzle. chief is also trying to help and just providing an alternative, which is scientifically possible I expect; if nothing else, I'm tempted by chief's idea just for the tinkering possibilities and smile of doing it with at home things (I love hackaday, the make blogs, how it works, instructables and such). Although, not_important is also correct in saying I can already get the gaseous and syphon take off cylinders, so getting to the liquid CO2 isn't so much of a problem, it's the nozzle I'm primarily bothered about, and getting a result that has a nice, large surface area that I can easily transfer without resorting to a hammer, saw or screw driver and lower surface areas of chunks over flake. As I say, I suspect this is as simple as a piece of plastic in the nozzle with some holes drilled in it, to spray the liquid as jets as opposed to a bulk. I notice that a number of the sellers of the premade nozzles are reluctant to take a photo at an angle which would reveal what the nozzle looks like from the end. I don't know if that's an accident or not, but it seems quite common. The rest of the nozzle is just plumbing pipe attached to a fitting for the tank (which I already have).

I live in the UK, obviously, and the anti-terrorism / drugs thing is raging just as hard as I think it will be in the US. Maybe even harder. E.g. in Europe, we now have new initiatives like REACH. Which essentially ask or require suppliers to track chemicals from the minute they land at the ports to the sale at the other end. Even still, renting syphon CO2 cylinders is not hard at all. They're used heavily by metal shops and paintballs, or pubs, bars and anyone dispensing fizzy drinks. In fact, when I went in to rent my last cylinder of N2, I had to convince the guy I needed N2 and not CO2.

Besides, if you're growing plants and think cylinders are the main issue, not your critical pH's and such, you're probably an idiot anyway and need some jail time in which to learn from the experts. :D

cheif, I have some numbers on fridge pumps and ideas that were similar to yours. I'll post them up when I've got a bit more time.

@Magpie

There in lies the difference between us. There is absolutely no chance I'd ever see dry ice at the grocery or hardware places here. I've literally never seen it. Honestly, there is only ONE 'supermarket' I've seen that even sells ice cubes in a bag, let alone dry ice. And, when shopping with the family, the girls will keep us in the places for three hours at a time as they look at clothes, so I have ample time to wander round picking things up. I also wander round with the trade catalogues for the hardware places in my hand and read them more often than 99%+ of religious people open their religious texts. So I expect I'd have seen it if it was there.

LN2 is a similar issue. I can easily get it, provided a buy a standard sized dewar and pay the hazmat fees to have them drive it round, and the gigantic rental on the specialized tank. The cylinder guys will not pour it off on tap, and there aren't a lot of small name cylinder companies here. Practically everyone rents the cylinders. I've only ever heard from one guy in the UK who'd bought his own inert cylinder for welding, and that's in over ten years of dwelling on so many forums about it I've lost count. The only other people who own them are SCUBA divers, because they either know people with a compressor, their club has one or they have one. I'm sure there are probably industrial users who would pour some LN2 for me, some of the metal workers likely have it, somewhere. But that means trolling through a huge number of people and driving a good few miles. I also don't need LN2 and it's temperature would probably be more of a problem for what I need cold things for; e.g. vapours solidifying rather than condensing, clogging glass up and risking popping it, it's solid CO2 I'm after.

@anotheronebitesthedust

Don't even get me started on that. :P

Thank you, thank you,
John

[Edited on 7-8-2010 by peach]

entropy51 - 6-8-2010 at 15:12

Quote: Originally posted by MagicJigPipe  

Quote:

Where I live, $ 300,000 will only buy one a small shack in a bad neighborhood.


Are you being pretentious? I assume you are because of your previous behavior (caustic personality). Calm down please.

Also, where do you live? It certainly can't be in the U.S. if anyone is to take your statement seriously. Maybe you could offer some proof...


[Edited on 8-6-2010 by MagicJigPipe]
It ain't Arkansas, dude. No double-wides allowed here.

I was complaining not bragging.

It is indeed in the good ole US of A. No need to prove anything. You can Google real estate listings for metro areas in the northeastern US and prove it to yourself.

peach - 6-8-2010 at 16:39

Quote: Originally posted by entropy51  
Quote: Originally posted by MagicJigPipe  

Quote:

Where I live, $ 300,000 will only buy one a small shack in a bad neighborhood.


Are you being pretentious? I assume you are because of your previous behavior (caustic personality). Calm down please.

Also, where do you live? It certainly can't be in the U.S. if anyone is to take your statement seriously. Maybe you could offer some proof...


[Edited on 8-6-2010 by MagicJigPipe]
It ain't Arkansas, dude. No double-wides allowed here.

I was complaining not bragging.

It is indeed in the good ole US of A. No need to prove anything. You can Google real estate listings for metro areas in the northeastern US and prove it to yourself.


The only experience I have of being in the US first hand is NC / SC. Perhaps our opinions on a 'normal house' differ, or Carolina is just bad example; I know a lot of US guys visit the UK and think London, York or Edinburgh is the same as the rest of England, when they're actually quite unique places. But the houses in Carolina looked absolutely insane compared to what I could buy with the same money here. And I don't live in a city here either, I live in one of the scummy areas. I actually thought about moving to Carolina it was that 'open' and cheap compared to here. I have a tiny, tiny back garden here, and live in a block. In Carolina, for less money, I can live live with no one around me to complain, dewy forests to wander around in and vast lakes full of little isles to have fun on. There's nothing like that here.

If you look at this map of crime in the UK, look to the left of the main part, where it bulges out (Wales, not the island, Ireland, to the far left) then move up and long to the the right where it rejoins with main part, I live around there, and have been knifed and ended up in hospital walking home. And the houses round here are still a lot more than I'd pay for something bigger and nicer in Carolina.

[Edited on 7-8-2010 by peach]

zed - 6-8-2010 at 19:53

Lotsa Cheap Real Estate in the US. But, not so much, in the fun places to live.

In my neighborhood, in Portland, houses start out at about 350.000 to 400,000. From there, they go up. Way up. San Francisco is about twice as expensive.

Ah, but Las Vegas......is becoming cheaper by the minute. The economic downturn is hitting Vegas hard. Houses cost about half as much in Vegas, as they do in Portland.

The question is, "Could you stand living there?"........

Even though, on the positive side, it is probably quite easy to buy Dry ice.

peach - 7-8-2010 at 01:08

@zed

Well, that's true of here as well. I'm discounting places like the center of New York and London. A normal rent on a flat in London is around £800 $1,275.60 a month for one within a half hour ride of work. Buying flats is like you say, you can expect to start seeing $300k for the same flat.

Houses around my place, in that bright red crime anomaly on the map... in my road they're about £200 - £250k, $300k+, in a high crime, none city area. People in London hate 'up north', because it's full of povo's and scum; it's like the US in reverse I guess.

Las Vegas would be a fairly funny place to live for a brit. It's kind of like London for Americans I guess, in that it's the stereotype people expect of the place. There a good few places around the UK that are similar stereotypes, like York. If you want to see really old, seriously wonky 'ye olde England', that's another place to visit. The Shambles there are a tiny row of shops that are hundreds upon hundreds of years old, and there's not a straight line anywhere to be seen. But I would like to visit a lot of different states, since I know they change a lot from place to place.

@chief

I have spent many years messing around with fridge pumps. Before I got a rotary - I have a BOC Edwards & Alcatel now, and probably more to come - I used to use the ubiquitous black compressors for vacuum work all the time.

The maximum vacuum I've seen one produce is around 30 mBar, which is about the theoretical maximum for a water aspirator. Perfect for cheap, effective filtrations. They're also not bad for pulling off solvents, roughly.

But one major issue with them when it comes to distillations is their pressure instability. Regardless of which I hook a gauge up to, after letting them run for five minutes +, the pump will go down to it's maximum, then 'go silent' as if it's stopped doing anything, the pressure will rise by 10 - 20mBar over two minutes or so, then the pump will 'restart' and drop the pressure again. The significant time it's spent at a higher pressure, coupled with the rapid drop means serious bumping issues are common, and the temperature will be all over the place. The cycle time is largely dominated by the slowly rising pressure. The pump down time at the end is seconds, meaning the liquid has had a good minute or two to accumulate heat, making it superheated within a few seconds when the pressure goes down again.

I have taken dual stage lab rotaries apart and got them pulling better than before, but I can't really work out why the fridge pumps do this. I contacted a few of the people who supply them to the white goods producers and didn't get a single reply. I've tried thinking of ways to prevent it, but really need to know why it's happening to do that successfully; why it only appears after the pump has warmed up.

Two in series will reduce the pressure to 10mBar. I'm not sure if the bumping cycle disappears with two in series, I haven't run them for long enough really (will check, as it'd be excellent for the cash strapped, gauge-less guys if it did, as they all pull a similar vacuum so it just needs to be stable for a rough idea on the phase transition points & temperatures). Also, I think too many people opt for the comparably ultra-low pressures of rotaries too often. E.g. if you're dealing with a low boiling solvent, by that I mean anything from 100C down, a rotary stands a good chance of putting it's condensing point sub-zero, making it a pain to stop it passing through without getting involved with dry ice. A fridge pump will get it off cold, but stands a better chance of not pulling it through the condenser at the same time.

You're talk about running them in positive pressure mode to condense CO2 is a wacky idea I had a while ago for cleaning up the atmosphere. The Russian Vostok weather station in Antarctica has recorded temperatures as low as -89.2C. Already below the melting point of CO2. It made me wonder if one could set up atmospheric processing in such areas that simply featured a fan / turbine system (possibly driven by other wind turbines, even mechanically, solar panels, tidal etc) to harvest the CO2 back. I'd say fusion, but that's not even working in experimental, city based plants, so the idea of dumping one out there and expecting it to be economical or maintenance free is a joke. Problems, protected remote regions, is the important jet stream flowing by at ground level & storing tens or more of Olympic sized swimming pools worth of it, per day (the production rate from global combustion). Maybe one could float little stations up on chords around the more populated regions, with compressors in them that run on panels unhindered by cloud in the cold, CO2 rich jet streams and drip it back down the tether.

Rambling aside... I have heard fridge compressors can produce worryingly high positive pressures for homebrew gear. To quantify that, 30 bar.

I just had a thought and tried running that through backwards, based on the compression ratio and, low and behold, it comes out as around 33mBar of vacuum, dead on the center of what I see mine producing (to the extent that I couldn't have planned it to work better, and suggesting there is a hint of truth to this).

If the same is true in reverse for rotaries, that equates a theoretical maximum of 28kpsi in the opposite direction. By which point, the seals will long ago have exploded. Still, it'd be interesting to see how high those seals will go. I have a sneaking suspicion, not as high as fridge pump, which features an all welded, sealed chamber; whereas a rotary is full of rubber seals and bolts; since it's only designed to deal with a 14psi difference

Here's another thread in which they're discussing 500psi+ pressures from a fridge pump. A reply has a reference to a book written by a guy maintains fridges / freezers / HVAC, and there's a reply from a guy who's tried it in person and had a copper pipe burst at 600psi, with the pump still functioning.

Wonder what two in series would manage. 100bar (~1400psi, 9MPa) says my calculator, based on the compression ratios and disregarding the seal problems at such massive positive pressures.

Makes me wonder about all this liquid air at home talk. Maybe worth consulting some more of the phase diagrams. From my very quick glance, those pressures and freezer temperatures are approaching the transition of nitrogen to a liquid state.

DANGER NERDS, DANGER!


[Edited on 7-8-2010 by peach]

entropy51 - 7-8-2010 at 06:08

Quote: Originally posted by zed  
Even though, on the positive side, it is probably quite easy to buy Dry ice.
Yep, if the beer and wine store is out of dry ice, the medical and welding gas supplier has it. The only time you can't find it is when there's a long power outage after a summer thunderstorm and people snap it up to keep their frozen food from thawing.

entropy51 - 7-8-2010 at 17:08

Quote: Originally posted by peach  
Quote:
Despite your protestations to the contrary, you do very much appear a gimp. Whatever that is. Smacks of bigotry if you ask me.


I asked a very simple question at the start of the thread and made it clear why I was asking it.

Would you care to elaborate on how I'm being a bigot?

I certainly would. Just as soon as you elaborate on what you meant by "gimp". After you do that, I think it will be crystal clear without any clarification from anyone.

Panache - 7-8-2010 at 21:53

this is a pretty stupid thread

peach - 8-8-2010 at 03:54

Quote: Originally posted by entropy51  
Quote: Originally posted by zed  
Even though, on the positive side, it is probably quite easy to buy Dry ice.
Yep, if the beer and wine store is out of dry ice, the medical and welding gas supplier has it. The only time you can't find it is when there's a long power outage after a summer thunderstorm and people snap it up to keep their frozen food from thawing.


You have to realize, that simply is not correct around the UK. In my entire life, I have never seen dry ice in a single public store around the UK. And I have been looking for it, as I'd obviously much rather hand over a £5 note and get a bag than bother will all this messing around with cylinders and nozzles.

There is only one supermarket here I've ever seen selling ice cubes in a bag. I've literally never seen a beer / wine store selling premade ice. And I know that in the US you have dispensers in hotels and things, sometimes free buckets of it in the hall. Nothing like that here. And that's frozen water.

I suppose the reverse example would be me saying, there are tea and cake shops all round here, so there should be in the US. It's not like that. The first thing I asked for in the US was a cup of tea, and all that was available was fruit tea.
Quote: Originally posted by entropy51  
I certainly would. Just as soon as you elaborate on what you meant by "gimp". After you do that, I think it will be crystal clear without any clarification from anyone.


Gimp; vastly deviating from the accepted norm, "weirdo", this;
Quote: Originally posted by Panache  
this is a pretty stupid thread


You mean the arguing? I can entirely agree with that. You mean me asking chemists for advice on how a dry ice nozzle works? No. And, if you mean the latter, it's questionable why you chose that one sentence reply of saying "Yes / no, it has a perforated plate".

Very simple question, no actual information from anyone regarding the nozzle.

Seems I'm going to have to actually buy one and post photos for y'all.

watson.fawkes - 8-8-2010 at 07:51

There is some brief information on CO2 nozzles available in this post; no pictures unfortunately.

peach - 8-8-2010 at 08:36

Quote: Originally posted by watson.fawkes  
There is some brief information on CO2 nozzles available in this post; no pictures unfortunately.


Thank you very much. Looks like Sauron may be able to help, if I can ever contact him, as he appears to have disappeared for the last few months.

Alternatively, I'll copy his nozzle, see how it works, then try the perforated plate if not.

It's interesting that he says;
Quote:
The important thing is that the dry ice come out only when you need it (JIT) and in slurriable form rather than in big blocks.


Indicating his own nozzle may be producing it thusly, or I have a suspicion he'd have mentioned it given him mentioning the form earlier on.

The mention of a 1/8" hole I think, at these large pressures, is likely acting as a spray forming orifice, like you'd see at the end of a swagged copper or brass welding or brazing tip; the bit that clogs when you fuck up and results in the popping and banging. It'll also be similar to the tip of a spray gun. In the welding example, the hole is relatively large but it's only supporting a flame. For the atomization in a spraygun, it's small and the pressure is "high" (~100psi, unless you're a hippy and using the inferior HV guns). The same single point is also used for misters and foggers, with tiny diameters and "high" pressures. For the CO2 tank, the pressure is huge by comparison (so the hole can be wider), and the desired flow rate is as well. Meaning the 1/8th hole could be forming the fan of CO2. If you think about it, why would he bother with the blanked fitting in the first place if it wasn't? He's obviously trying to show how cheap and easily it can be done, so it wouldn't make sense to include it if there was no logic behind it.

I did a UTFSE prior to posting, but didn't get that post, because I made the heinous error of not selecting 'topics only'.

Right, I'll disappear for a while and hopefully reappear with some photos.

John

[Edited on 8-8-2010 by peach]

Nicodem - 8-8-2010 at 13:17

You don't need any perforated plates or whatever. Essentially it is just a tube with a few mm large hole prolonged into a cone where you attach the cloth bag to collect the dry ice. At least that is how the one I use look like. The dry ice forms from expansion of the liquid CO2 so I don't really see what role a perforated plate is supposed to have. All you need to pay attention is the vertical red arrow sign on the bomb. If there is one then the bomb has a vertical inner tube and you must not invert it in order to draw out CO2 in liquid form. If there is no arrow you need to invert it which means you need a special stand for safe use.

peach - 8-8-2010 at 16:24

Quote: Originally posted by Nicodem  
You don't need any perforated plates or whatever. Essentially it is just a tube with a few mm large hole prolonged into a cone where you attach the cloth bag to collect the dry ice. At least that is how the one I use look like. The dry ice forms from expansion of the liquid CO2 so I don't really see what role a perforated plate is supposed to have. All you need to pay attention is the vertical red arrow sign on the bomb. If there is one then the bomb has a vertical inner tube and you must not invert it in order to draw out CO2 in liquid form. If there is no arrow you need to invert it which means you need a special stand for safe use.


Thanks Nicodem, this seems pretty easy now I have two references for the actual nozzles themselves. I'll see if I can pick the bits up next week. I may only need a blank.

In the UK, the syphon / stinger tanks have a solid white line down the side, for anyone in the UK who's wondering when they see one. BOC refer to them as 'dip tube' cylinders. The one on the left is such;

peach - 5-9-2010 at 17:54

Quote: Originally posted by chief  
Who really desperately needs it could try
==> to connect 2 refrigerator-compressors in series ...
==> and compress some CO2 into a reservoir within a deep-cooling fridge ...

At the -20 [Cels] that such a fridge can do (-35 with disabled temperature-regulation)
==> the liquefieing-pressure of the CO2 could be in range for the 2 fridge-compressors (in series) ...

So the CO2 could come from some burning of anything or wherefrom ever ...
==> Only that the N2 from the air might disturb the efficiency ...


CHIEF, YOU AND YOUR IDEA GET A MENTION IN THE VIDEOS IN THIS THREAD

[Edited on 6-9-2010 by peach]