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Is it possible and safe to use liquid nitrogen to quickly cool a 5 gallon tank of liquid from room teperature to say 34 °F? Or is there another way that can produce really fast results?

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  • $\begingroup$ Which liquid are thinking of? $\endgroup$ – user2617804 Aug 22 '15 at 6:47
  • $\begingroup$ Liquids are coffees, fruit juices, and water. $\endgroup$ – Eddie Chow Aug 22 '15 at 6:59
  • $\begingroup$ Liquid nitrogen will freeze them to a little bit lower than 34 degrees Fahrenheit. Like, 50 degrees colder. And this question has a big lack of data. What is the specific heat of that liquid? How will you use or pour liquid nitrogen? Do you even have access to it? $\endgroup$ – M.A.R. Aug 22 '15 at 7:22
  • $\begingroup$ Sorry for the lack of information, I am using this in a restaurant environment and have heard that this is possible but just cant find the specific details on how to do it or if it is the best way. The starting temp would be about 23°c(73°f) and want to cool to 0°c(32°f). I am wondering if this is possible, I understand that pouring the liquid into the liquid nitrogen and mixing is the better way. I do have access to it, I just wanted to know if this is a good way to do it or if there are better alternatives before I try it, as it seems to be potentially dangerous. $\endgroup$ – Eddie Chow Aug 22 '15 at 7:54
  • $\begingroup$ Dippin' Dots.... Made with LN2 $\endgroup$ – Jon Custer Aug 22 '15 at 12:11
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I don't know whether liquid nitrogen can be used to cool a volume as large as 5 gallons safely (that is a lot to do at once in a kitchen or restaurant) but it can and has been used in cooking.

Here is an example from youtube.

But it can be dangerous if not done carefully. This BBC story has a warning of what happens if it isn't.

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Is it possible and safe to use liquid nitrogen to quickly cool a 5 gallon tank of liquid from room teperature to say 34 °F? Or is there another way that can produce really fast results?

No, at least not in a safe way. For rapid cooling of such volumes, intense stirring is needed. Liquid nitrogen tends to stay on top of the heavier water and evaporates very easy. It shall form an ice layer with rest of the liquid relatively unaffected.

Possible solutions is food-grade dry ice that is denser than water and causes stirring if submerged thanks to bubbles formed from it. It shall still require good ventilation, but might work.

BTW, both options likely are extremely cost-inefficient.

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Pouring LN2 into a volume of warm water would produce a VIOLENT effect of converting the LN2 into a large volume of gas:

https://youtu.be/rVi58N25-Zc

I treat LN2 with the same respect that I do gasoline. It has an expansion rate of 1:694 at 20 °C (68 °F) and it is quite dangerous to wet human flesh and especially the eyes which are always wet. Dry skin doesn't freeze instantly but wet surfaces conduct heat at a 25X higher rate.

So you must consider playing with LN2 the same as as playing with fire. If you must use LN2 to cool water I suggest a heat exchanger system where the exhaust is routed to a well ventilated room. Better yet use another refrigerant in a closed cycle arrangement.

I work for a large chemistry department that routinely uses ~1000 Liters of LN2 a week. I am also the safety officer and if anyone suggested such a plan to me they would be shutdown immediately.

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    $\begingroup$ One safer way would be to put water ice into the LN2 and transfer the super-cooled ice cubes using a strainer into the bucket of water you wish to cool. They will cool the water Much Much faster than normally cooled ice. $\endgroup$ – 3dalliance Jul 16 '16 at 16:00
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    $\begingroup$ Also you should have cryogenic gloves, face-shield and apron to be on the safe side. $\endgroup$ – 3dalliance Jul 16 '16 at 16:02
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I used to do this often for a chemistry demonstration for an organization I was in.

We would mix up a fruit punch with kool aid, soda, maybe some fruit cocktail, etc and pour liquid nitrogen on top to flash freeze into slushies.

Honestly, it didn't work well since it basically just froze the top and left the bottom undisturbed. The key was to pour it incredibly slowly, stir vigorously and take breaks (because of the massive cloud of nitrogen that would result).

Edit: Let me also make it perfectly clear that all possible precautions were taken including goggles, cryo-gloves, lab coats, well-ventilated area, etc.

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