Quote:
Originally posted by FishaOfMen
I don’t appreciate the flames. I was looking for assistance, not thread crap. Alchemy & ezlid, you guys provided no quantitative information on LN2 to copper heat transfer whatsoever.
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I'm sorry you feel this way. As far as using LN2, there are many safety concerns and we are trying to make you aware.
Also your original post isn't very clear on your intent. You said and I quote " I'm going to take on the project of LN2 and dry ice cooling" and you talked about and I quote again "Creating my own container out of a solid block of copper. It would stand about 9" tall x 4" wide x 4" deep. There would be a bunch of pins coming from the bottom. I wouldn't have any pins in the center so that I could throw dry ice chunks in the middle. Near the outer edge, I'd have a passage so that a mixing wand could be continually mixing the coolant in a circular motion." Since you never said what you were really planning and by the post title, I assumed the "coolant" to be LN2" If you are asking for help, be clear in what you are asking and don't bitch about people demonstrating concern for YOUR welfare. I don't normally do this, I'd rather post a link but I want you to see this:
Safety Notes & Concerns
Liquid nitrogen is a dangerous material. The following is an excerpt from the Air Products Nitrogen Material Safety Data Sheet:
A back of the envelope calculation indicates that the entire contents of a 10 Liter dewar being spilled in a unventilated 274 square foot room with an 8 foot ceiling would reduce oxygen levels below the 19.5% level where Air Products recommends the use of a respirator. Since most classrooms are larger than this, suffocation does not represent a major danger. When transporting the liquid in a car, however, it is probably a good idea to open a window.
The possibility of freeze burns represents a much more serious danger and is therefore our first concern. This does not mean that the demonstration itself is dangerous, but it does mean you must be careful. Dangers include:
Nitrogen can spatter (possibly in eyes) while being poured.
Flying chunks of frozen objects could cause eye injury.
Students (being children) will want to reach out and touch nitrogen or other cold objects. As mentioned above, contact with nitrogen can cause tissue damage, and this must be prevented.
Therefore specific safety precautions should include:
Teachers must stress to their students the importance of not touching frozen objects or nitrogen.
Wear goggles whenever pouring or dumping nitrogen. Nitrogen can spatter into the eyes, and potentially blinding pieces of frozen things can fly around when we drop it.
Use a glove and / or tongs to handle any object going into or out of nitrogen and to carry the nitrogen dewar.
Teachers should familiarize themselves with the following first aid instructions (excerpted from the Air Products Nitrogen Material Safety Data Sheet) for cryogenic freeze burns just in case the worst happens:
If cryogenic liquid or cold boil off contacts a worker's skin or eyes, frozen tissues should be flooded or soaked with tepid water (105-115F, 41-46C). DO NOT USE HOT WATER. Cryogenic burns which result in blistering or deeper tissue freezing should be seen promptly by a physician.
Remember to stress the importance of not touching liquid nitrogen or frozen objects.
I have not seen any posted remarks about ventilation and oxygen displacement, so of course only try this in a well vemtilated room. You know how cold this stuff is.
Which brings me to giving some quantitative analysis for you. LN2 is 77 K, or -320.8 F / -196 C. At those temps the heat transfer quality of the heat sink material, be it Cu, Al, Ag or a brick, is inconsequential. Oh, BTW - the heat transfer qualities of a material doesn't change because you use a different coolant, does it?
And one more analytical fact for you, actually a question for you. How do you induce turbulance into boiling LN2? Maybe there isn't a lesson to be learned on that one.
On second thought, I'm not sorry you feel the way you because it just showed your ignorance and laziness to do some research on your own. At least bring something to the the table before you ask others to do some work for you.
Sorry to all for the long post, folks.