Has anyone ever invented a practical microwave-freezer?

You can get water from room temperature to boiling in under a minute, but how could you get it from room temperature to freezing in about 2? Obviously I'm referring to more than just speed freezing water, could be useful for other stuff too. I was just wondering if it was even theoretically possible to make something that did this.

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Things are hotter when they have more energy stored within them in the form of heat, which is simply a state where the particles of the thing are more excited. Things cool down as heat is released from them and the particles lose some of their energy. We do not have any form of "energy" that can be introduced into a random object in order to cause its particles to become less excited. Simply put, any device that imparts energy into an object will likely heat it up, not cool it down. Barring the discovery and mastery of anti-energies, we won't see anything like it anytime soon. So nobody's invented a freeze ray. No. There are ways to cool something, chemical reactions, peltier devices, use of liquid nitrogen or another cold substance, exposure to outer-space, etc. Choice of methodology, time to freezing, and efficiency all depend on hundreds of factors. How well does the material to be frozen insulate it's centre? How large is the thing to be frozen? And many more questions that mean there is no one answer to "how, how well, how much, and how long."
negu744 years ago
I recall reading in maybe popular science about 20 yrs ago, that someone had invented what they were calling a 'macrowave' that freezes via a similar principle to the microwave- it created resonance in water molecules that slowed the spinning. The only problem was heat.and practiciality- one couldn't destroy heat that the food would give off, only exchange it. So when you 'froze' food inside it, you'd literally be pumping heat out of that localized system- then you'd also have to pipe the heat to the outside of the house, like a central ac. This didn't take off becuase it's very impractical, but in principle I'm sure there is a patent for it. I'd not try to google it because a similar product is called a 'macrowave' that heats, and I've not been able to find this article on the interwebs. Just too old, it's more microfiche era.
mikedu7 years ago
Intriguing. Don't you guys ever wonder how the peltier effect works? Its a semiconductor that freezes if electric current is applied to it. If you have the right frequency, buldings and bridges can topple down. Maybe that freeze ray isnt so far off, especially for pure solid structures; It just needs the proper conditions for something like lasers to give it the right cancellation wave to make it more calm. Eventually, it will freeze.
a Reverse Microwave! try watching Haggard with Bam Margera, thats funny
gentry8 years ago
One point no one has brought up is that you can chill, say, a bottle of wine in 15 minutes by putting it in circulating icewater. Putting something in the refrigerator is much slower because water is something like 25 times better at conducting heat than air. It is fun to make instant ice cream with liquid nitrogen, but is definitely not the safest thing to do. Don't splash your eye and blind yourself!
ewilhelm8 years ago
I've been dreaming about this for a while now. Entropy tends to get in the way of building a practical device, but if someone figures it out, I hope they call it a "coolowave."
You might be able to flash freeze stuff - by pressurizing it up to a high pressure then completely depressurizing almost instantly, it might squish the food a bit though, how well would pastries hold up to this?
Actually, 'freeze rays' have been used in ultra-low-temperature physics experiments. They would not be terribly practical for making ice cream, though.
A microwave-freezer? My microwave freezes just as fast as everything else when I put it in my freezer. I have to take out the ice cream to make room for it though. But I usually don't freeze mine. I've never had one spoil yet. :)

Here's the calculation for cooling one pint of water from room temperature down to freezing in two minutes:

  • 4.1813 J/g/K = energy to change the temperature of one gram of water by one Celsius degree
  • 22 K = temperature difference between 72F and 32F
  • 1 g/mL = density of water
  • 473 mL = one pint
  • 120 s = two minutes
4.1813 J/g/K * 22 K * 1 g/mL * 473 mL = 43,511 J

43,511 J / 120 s = 363 W

So this requires 363 Watts of heat-moving power. Multiply this number by about three times to get the input power of an regular freezer with this ability, or by about twenty times if you are using a Peltier heat pump. (Thermoelectrics are not good for moving so much heat quickly.)

Note that turning water at the freezing point to ice at the freezing point requires a moving a considerable amount of additional energy. In this case, you need to add 157,769 J to the above amount of energy before calculating the power.

  • 333.55 J/g = heat of fusion for water
333.55 J/g * 1 g/mL * 473 mL = 157,769 J

Some restaurants have cold plates for this purpose, but they are not cheap. Liquid nitrogen is an excellent way of removing heat and quite inexpensive besides. Unfortunately, the equipment for storing and regulating the flow of liquid nitrogen is expensive.

So if you want to cool things quickly and cheaply but do not want to deal with liquid nitrogen, you might want to try this Instructable: use alcohol to transfer heat to dry ice from the thing you want to cool.

NobodyInParticular mentions liquid nitrogen and the relative complexity of storing and regulating it. I work in an industry that sometimes uses LN2 in material processing. LN2 would do the trick, but well beyond the cost and complexity of storage and regulating its flow, is the EXTREME danger of anything at -196C (-320.8F). Most of us have seen the science experiment of instantly freezing a rose that can then be shattered by lightly tapping it on a tabletop. The same thing will happen to flesh, limbs, etc. and unlike the frost-nip (pre-frostbite) that you might experience in the wintertime . . . your body will NOT recover from the experience. Yes, the same thing will happen to your flesh that happens with the flower. I suffered momentary exposure on my knees to liquid propane at -42C (43.6F) twenty-five years ago and am still dealing with the medical aspects of the injury. Remember, the injuries you suffer today . . . will come back to haunt you in ways you never imagined in twenty-five years. For your own safety always remember, Dick’s Law. DICK’s LAW is: Never put your hand . . . anywhere you would not put your ???!
McDouche (author)  NobodyInParticular8 years ago
I... I get the feeling you've tried this before...
Actually, I have not and probably will not have an opportunity to try the industrial freezer, Peltier freezer, cold plate, or liquid nitrogen ideas. But the dry ice mixed with alcohol looks impressive and very easy. I might give that a try in the near future.

In case you were wondering about the calculation, that was more a matter of my curiosity than anything. I knew water was a very hard material to freeze, but I wanted to know how hard. It is also a great demonstration of Google Calculator.
I had this idea in hot summer '86 in Bristol UK, while trying to find some cool drinks in a service station.
"Why can't we lower the frequency of the wave and hey presto the water molecule starts slowing its own frequency". But later I found out it is not quite right. Read this:
http://www.lsbu.ac.uk/water/vibrat.html
And this:
http://www.lsbu.ac.uk/water/microwave.html
For further education.
microwaves work by spinning the water molecules around and the friction generate heat. they have blast freezers that work by a blower blasting cold air onto products like meat carcasses and things like that but that is about it. Its used in the food industry because you only have a couple hours for food to get safe temperatures.