Cheaper than dry ice?

oic0

oic0

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Jun 16, 2012
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I havent gotten to cryo anything yet but I was looking at the temp of dry ice. Its about -110 degrees? Has anyone tried a cascade cooler as a reusable solution? Either peltier or refrigerant. I would think it would be a lot cheaper due to reusability.
The general idea is that a peltier or refrigerant system can only achieve a certain temperature delta so they are stacked. I see some cascade peltier modules for sale that can do a 90-120 *C delta. No idea how much they cost though and then you need to power them and dissipate their sizeable heat production somehow. I have only played with single modules (variable price, my large one cost $25) and powered em with cheap server power supples (paid $7 for 575 watts of 12v). If no one else has tried it, I may just for the heck of it. I know a prontera unit (refrigerant not peltier) would work since they can cool a cpu producing lots of heat to -100 or lower, but they are quite expensive.
 
Commercial metal working shops sometimes have vessels for and even sometimes have liquid nitrogen in them, can't hurt to ask if you can dip a blade in it.
 
from what i've read on cryo you have to cool the blades substantially (at least dry ice first) before you do liquid nitrogen otherwise the thermal shock can make the steel to brittle even after a temper, or just crack it. this study was on en 353 steel (carburized to ~1%c) for the gear industry but i assume that the problem would be just as bad if not more so in tool steels. anyway, i wouldn't plunge strait into n2(l) without a good prior cooling.
http://www.gearsolutions.com/media/uploads/assets/PDF/Articles/Oct_11/1011_300Below.pdf

im not sure on refrigeration methods but please keep us posted on what you end up doing, id love to hear.
 
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Dry ice is very cheap

Im seeing online quotes for 1 to 3 $ per pound.



The last ultra low freezer I saw was a dual stage refrigeration that only went to -85C and took two days to reach that.
Price ? I think it was $50,000



The Peltier devices I've seen are in those car battery powered coolers and they don't even work for that compared to regular ice.

Not only temp delta, be sure to look at the other specs,
A 100degree temp change on very very small thermal mass won't work well.

It's not just temperature, it's also rate of cooling .



You're still going to have some quench medium like acetone.
How can you insulate the hot and cold side and keep the acetone away from the heat source ?



but go ahead and try it if you want to .
 
12345678910 said:
You're still going to have some quench medium like acetone.
How can you insulate the hot and cold side and keep the acetone away from the heat source ?



but go ahead and try it if you want to .
Click to expand...

Have you seen the tubes they use to supercool CPUs? I was thinking that but in reverse. The peltiers up against the small copper plate on the bottom that would normally press against the cpu heat spreader and the steel inside submerged in the tube where the LN2 or dry ice is usually kept. Then you cool the hotside with some other system, like a CPU water cooling system. I found a peltier with a high enough delta, it costs $80. The water cooling for the hot side would cost $100. Then I just need copper pipe, a heatsink to cut up and use as the base plate, and some good insulation. Perhaps I should work on my math skills so I can calculate if it would work or not :foot: before I go spending money.
 
I'm paying $1.60 per pound of dry ice and use like 3 pounds at a time--- pretty cheap.
Every now and then my neighbor will stop by with 15-20 pounds of it and then it costs
0. Again pretty cheap.
Ken.
 
When I do D2 blades I try to do about 5 at a time. So the dry ice bill is just a little over a $1 a blade. If I go any other way its going to be liquid N2
 
You will need to calculate the heat exchange at temperature. To get your steel to temperature your refrigerator will need to be super insulated. Your system will need to remove enough heat to cool the steel and the refrigerator and to compensate for heat lost through the refrigerator. As the temperature of your system decreases the heat loss will increase. I am not certain your system will be able to remove the heat fast enough to compensate for the losses.
 
you guys using dry ice, are you using Methanol or Isopropanol or Acetone as a medium?
 
I have been using kerosene, but, am going to go to an alcohol because i don't like the amount of foam I get when I mix the kerosene with the dry ice or the dry ice with the kerosene. I have also started looking for a small old style cream can to use for this and store the alcohol.

But this thread made me think and I did a search for home made liquid nitrogen plant and bingo


http://benkrasnow.blogspot.com/2008/08/diy-liquid-nitrogen-generator.html

It seems the difficult part was finding the filter for producing the dry N2 to start the process. I am wondering how it would work to just start with a bottle of compressed N2 untill I could round up the parts for the nitrogen filter
 
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But would you need the liquid nitrogen? Couldn't you just cool the steel directly? Or rather a heat spreading plate the steel sits on all wrapped in a bunch of insulation.
 
oic0 said:
But would you need the liquid nitrogen? Couldn't you just cool the steel directly? Or rather a heat spreading plate the steel sits on all wrapped in a bunch of insulation.
Click to expand...

Not with the system you describe. However, your knife blade is much more massive than the CPU that you reference. Perhaps, several of these devices on 2 plates with the blade inside?
 
oic0 said:
But would you need the liquid nitrogen? Couldn't you just cool the steel directly? Or rather a heat spreading plate the steel sits on all wrapped in a bunch of insulation.
Click to expand...

No, you do not need the liquid N2, But, dropping the blade to its temp has advantages over just cooling the blade to -100f. -100f will get rid of retain austinsite, but will not cause any effect on carbides where the -312f of N2 will.
 
oic0 said:
But would you need the liquid nitrogen? Couldn't you just cool the steel directly? Or rather a heat spreading plate the steel sits on all wrapped in a bunch of insulation.
Click to expand...

What steel are you using? There is no advantage to dropping to LN temperatures for a number of steels.
 
SteelSlaver said:
No, you do not need the liquid N2, But, dropping the blade to its temp has advantages over just cooling the blade to -100f. -100f will get rid of retain austinsite, but will not cause any effect on carbides where the -312f of N2 will.
Click to expand...
That's what I mean though. Instead of super cooling the heatsink and carefully feeding it pure nitrogen, put a plate on the cooling head and attach the knife to it, maybe with a small embedded neodymium magnet to keep it in good contact without any mechanical stress that might crack it when it gets brittle, and cool the steel directly. That would be a much simpler machine than all the extra stuff required to produce pure gas.
 
It may work if you got a cryocooler like the guy in the link I posted used for his liquid N2 generator. He initially just hung it in a thermos bottle and after a while had liquid gas in the bottom of the thermos. So if you attached on firmly to a blade and inserted it into something like a thermos I would think the blade would eventually reach a temp at or near that of liquid N2. Basically make the knife part of the heat sink.
His set up took 12-16 hours to initially cool the dewar and another 24 to produce a liter of liquid N2 at a cost of $1.10 of electricity per liter. So a knife done like you propose would take a couple days and a couple bucks worth of electricity. Less for the electricity because you would not be running the additional components in his assembly. HMMMMMMMMMMMMMMMMMMM
 
As long as you buy the Dewar (container to transport) you want, the liquid Nitrogen is only $1.75 per liter or so, and you don't need solvents, and it's inert gas, and it completely vaporizes and disappears without being explosive, dangerous, or damaging to the atmosphere. You don't need a N2 filter or system to generate it yourself (expensive and unnecessary unless it's all you do all day), you just need a container and a company like Airgas to buy it from. Less equipment, space, etc. and $10 or so per day/batch of heat treating. I've never understood dry ice and acetone- true many steels don't need LN temps, but it doesn't hurt anything and is useful for most any complex alloy, while dry ice only helps with RA and doesn't do anything else.
 
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