RSSBirdchick lives in Minnesota, where it's wicked cold right now! She shot this video of what happens when you spray hot water at -20 degrees F. So are those threads of ice dropping down, anyone know exactly what is happening?
Spraying hot water at -20F
Posted by Patti Schiendelman |
Jan 15, 2009 12:58 PM
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Sorta the opposite of sublimination "Deposition" from wiki http://en.wikipedia.org/wiki/Deposition_(physics)
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We can do that here in Omaha today too! Here's my guess.
Liquid water has a probability of kicking out water molecules from it's surface, resulting in evaporation, even well below the boiling point (or even below the freezing point). This is why room temperature water will evaporate. This occurs until the vapor pressure of the water comes into equilibrium with the atmosphere around it. Heating the water increases it's vapor pressure, resulting in more evaporation.
So the hot water droplets emitted from the spray bottle immediately start throwing out lots of hot water molecules, which rapidly cool. Because the air is very cold it has a relatively low capacity to carry water vapor. The molecules of water condense into a fog of very small water droplets which drift away.
The streamers that can be seen on the video are large droplets of hot water that are issuing condensing vapor which are left behind as white trails.
In the winter I keep my house fairly chilly, 52F at night, 58F during the day. Any hot water makes great clouds of vapor. A 100F bath tub is a visual treat, as it steams like a hot spring for as long as you care to sit in it.
This morning it was about -10F while I was driving to work, and I noticed that in a line of cars just pulling away from a traffic light that the clouds of fog from tailpipes was so dense that it was making it difficult to see the car in front of me. Normally these water clouds evaporate into the air very quickly, but on a day like today they take much longer to vanish.
It's also fun to see the heating exhaust from a housing division as the sun rises and illuminates the plumes from behind.
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There are two things going on here that combine the spray into a very thick ice fog. floating ice crystals. This is just a theory based on my observations, nothing I've really sat down with a microscope and proven.
1) the evaporative cooling effect from the hot water. When vapor pressure is equal to or greater than atmospheric pressure, water boils, independent of whatever temperature the water is. The vapor pressure of the water is very high, since it's probably around 180F. (Tea kettle water is crazy hot, at least from mine.) The atmospheric pressure of the surrounding air is relatively low, because of the drastically low temperature. This more or less forces the sprayed water to evaporate as soon as it leaves the bottle. Evaporation causes cooling, which very quickly cools the water to near freezing.
2) the outside temperature is damned cold. The ambient temp takes the sprayed water temp down further and will eventually freeze the water, producing that thick ice fog. (I'm assuming that's an ice fog.)
I would be willing to bet that if she sprayed that on something that it would produce some really beautiful results, and if she could produce an even finer mist she could create snow.
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can you post a high-res or a slomo version? i can't see what's happening because of the compression artifacts.
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I think the process "Edy's Slow Churn" is referring to is "diabatic cooling". The water is losing temperature with evaporation, which is actually making it denser. That is, I believe, only half of the equation though.
The reason why it condenses into ice quicker as hot water is because there is more "latent heat" that can be released as a result of the temperature change (delta T). Energy always moves from warm to cold more readily. When you have more available heat (in the form of hot water in this case), it warms the air around it more readily, thus causing heat to be lost very quickly in the water. This wouldn't work very well for water that was just above freezing, because there is hardly any energy to be released in relation to the cold air around it. The more latent heat released from the water, the easier it is for it to go from the somewhat unordered state of liquid to the ordered state of a solid.
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I think the process "Edy's Slow Churn" is referring to is "diabatic cooling". The water is losing temperature with evaporation, which is actually making it denser. That is, I believe, only half of the equation though.
The reason why it condenses into ice quicker as hot water is because there is more "latent heat" that can be released as a result of the temperature change (delta T). Energy always moves from warm to cold more readily. When you have more available heat (in the form of hot water in this case), it warms the air around it more readily, thus causing heat to be lost very quickly in the water. This wouldn't work very well for water that was just above freezing, because there is hardly any energy to be released in relation to the cold air around it. The more latent heat released from the water, the easier it is for it to go from the somewhat unordered state of liquid to the ordered state of a solid.
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Look like a snow making machine from a ski hill.
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For som water to lose enough energy to actually freeze, it causes other water molecules to absorb the energy and heat up and turn to vapor. With a big shock of trying to lose the heat to become stable, some water molecules will actually absorb the heat and evaporate.
So you actually see all three phases of water at this time. The heat to give off is more as the temperature difference between hot water and the air increases. dH=k(T1-T2)
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We're in the Twin Cities area too. My wife was talking with a friend of hers from Arizona and trying to explain just how cold it is.
She said, "Go stick your head in your freezer. Now... it's 20 degrees COLDER than that outside here"
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very cool indeed. birdchick is attractive.
(edited a bit for language, but sentiment retained)
Patti :)
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mpemba effect
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It's ethereal tendrils of boredom. It happens to you when you live in Minnesota for a sufficient period of time. The primarily cause is years of constant freezing and thawing of one's brain. Eventually, you come to believe that it is "fun" to stand outside in -20 degree temperatures spraying water from a bottle :-)
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Yea live in wisconsin. It has been way to cold the last 2 weeks. -20 today, -15 yesterday, colder tomorrow. I love WINTER....
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Pretty neat, Birdchick! I've never seen it with a sprayer before, but it's also pretty impressive if you just take a pan of hot water & fling the entire contents into the air and watch the resultant cloud of snow drifting away.
PS: Greetings from New Brighton, MN!
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I live in the Twin Cities as well. Its not THAT cold. I was playing with my dog today with a t-shirt.
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I discovered this by accident. Just turn the fan on in your subzero-cold car and breathe toward the windshield. Your breath will turn into snowflakes which will land nicely on your dashboard!
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what's -20 in real temperature. e.g. centigrade
http://tinyurl.com/7b77hn
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Do this with a high pressure steamer. The amount of fog you get is amazing. I did it at about 5 deg which is the lowest it gets in my part of australia.
By the way enjoy the cold I recorded 49.9C ambient temperature today.
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as deposition is from a gas to solid, without the inbetween. Since it's hot water, and not steam, its just the regular freezing process, sped up.
Adding the atomizer in the bottle probably makes it a different effect though.
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I believe this is caused because of the Mpemba effect http://en.wikipedia.org/wiki/Mpemba_effect
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That is pretty cool. I wish I had such low temps to play around with, I'm located in Philly,PA. We don't see much lower then 5 degrees F.
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hot water actually freezes faster than cool water. this trick only works with hot water. if it was cold water in the bottle, it would still spray out as water.
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The "threads" are just larger droplets falling to the ground faster than the surrounding frozen cloud. As they lose water to the air, that lost water freezes and slows down, leaving basically the same thing as a jet contrail.
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This is the dumbest thing I have ever seen...
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This is one of the many weird things water can do. Here's a decent summary of all sorts of interesting crud about water:
http://www.neatorama.com/2008/08/22/5-really-weird-things-about-water/
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Cool, you guys, I don't think I've ever learned so much from the comments before, thanks!
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-20? that's a warm day here in Quebec.
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I had much more fun as a kid blowing bubbles at -30 and below; sometimes they still float even though they hit the ground solid and start rolling :)
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it's -14 right now in pittsburgh. we're almost there!
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Wow steam. What a surprise.
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Wow..steam. What a surprise.
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Its cold like that here in NE as well!! I should go try this!
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Am probably a bit late now asking this but what would happen if you tried one of those ultrasonic foggers at such cold temperatures? Would it work? And what would happen to the fog in the freezing cold if there was any?
Nice to be in the Southern Hemisphere. It's 27C here now!
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I used to live in Wisconsin and when it was -20F we would blow soap bubbles which would freeze as they floated in the air. They're really quite beautiful. Someone up in the hinterlands should give it a try and post a video!
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