Produce Ice Faster

[Enthalpy]

Hello you all!

 

Common industrial methods to produce (water) ice are:

• For ice blocks, put water in flat containers, chill from the outside by a liquid circulated between many containers.
• For ice chunks, chill metal tubes by a liquid circulating inside, pour water outside, break the obtained ice regularly.
• For ice chips, put water droplets in a cold gas.

Droplets won't make thick ice, and the first two methods limit the thickness or take too long, because of water's freezing heat (335kJ/kg or 308MJ/m³) and ice's heat conductivity (1.7W/m/K). If you allow an efficient cold plate to be at -10°C, the slowness of growth is 18,000,000s/m at 1m thickness, and:

• 1mm takes 9.1s, 1m takes 105 days
• 1min freezes 0.85mm, 1h freezes 6.6mm, 10h freeze 21mm

so flat metal moulds dipping in a circulating liquid at -10°C produce plates 40mm thick in 10 nightly hours. -40°C would only double the thickness and cost more energy.

 

I propose instead to grow ice at the surface of already existing ice, hence by the stored cold, but the pre-existing ice is cooled from its growing face, thus speed isn't limited by heat conduction through the ice.

• One machine raises the existing ice against a cold plate (not too rigid) for a few seconds, then sinks it less than 1mm under the water level for a few seconds (possibly aided by a wave), so all the new water layer freezes (important to stabilize an even surface). One cycle gains about 0.5mm in 20s, so the thickness gains 90mm per hour. Less thickness per cycle would increase the rate.
• If the ice can be grown around a mandrel, then existing ice is cooled by gas or a liquid bath or jets on a fraction of a turn, and the proper small amount of additional water is brought (spray, bath, brush, sponge...) during the rest of the turn. Cooling and water can alternate several times a turn.
• Or build a large head that moves (for instance with small circular oscillations) over the growing ice face. It carries many nozzles blowing cold gas and many water pipettes, for instance in an alternating pattern like a chessboard.
• In a continuous process variant of the many nozzles and pipettes, the thickening bar passes under gates or a continous roof blowing cold gas and adding a bit of water.

These machines are energy-efficient, as they need little more cold than the latent heat of fusion, and at a temperature not much colder than 0°C. The three last ones can be nicely fast.

 

Because water ends freezing at its free surface, the produced ice is compact, clear and bubble-free - nice for sculptures.

 

In circumstances where electricity production constraints daytime peak demand, for instance in Japan after Fukushima's disaster, ice produced at night to cool houses during the day is a possible contribution to even electricity consumption.

 

Marc Schaefer, aka Enthalpy

[Roquentin]

This is a cool idea and I suggest you make a graphic to illustrate it better. Still, my initial thoughts:

How would the strength of this ice compare with ice frozen at the freezing end? Ice formed the regular way is necessarily continuous as there is no layered freezing, however in your method there might be (I can't be sure without running an experiment) some consequence of the layers that are formed. Either that the formed layers won't be clear (which I think is less of an issue) or the formed ice would have less inter-layer continuity and might somehow be weaker. Once again, this is speculation so experiments are needed, which you could probably run in your freezer.

One solution I can think of if this were the case would be to apply pressure on the ice, or form it at a high end temperature that the crystal layers don't form very quickly and hence might have more time to 'merge' with one another.

Thoughts on my thoughts?

Edited October 6, 2013 by Roquentin

[Enthalpy]

Thanks for your interest!

 

A drawing, yes... I ought to, among other things... Already noted in the "to do" list, but a long time ago. In 2011, when I published the idea (badly redacted) elsewhere.

 

How strong, as you say: it must be tried. I consider it will resemble very closely black ice, which forms by rain on roads in cold air - the process is the same. I feel it's hard, but this is not a measure.

 

Similar processes happen at an ice rink, where ice uses to be hard. I guess liquid water melts a little bit if the preexisting ice before freezing, and this makes the good interface.

 

One fundamental difference: as usual processes freeze water outside in, gas repelled by the crystallization concentrate at the center point (ice cube) or center plane (ice plate). This is a mechanical weak point, and is unaesthetic in sculptures. In contrast, pouring new water at the free surface permits gas to escape the freezing front.

[Enthalpy]

Finally, sketches of the machines with many nozzles and pipettes. Real machines will have many more than sketched to be compact and fast. The cooling gas can be air. The water can be pre-cooled around the freezing point.

 

The batch machine can let the head oscillate to spread water drops better, while the continuous process machine can offset the pipettes over the rows. Experiments will tell better if drops splattering and rolling need these measures at all; black ice does not. Injectors would create smaller droplets than pipettes do, but the water must not freeze before touching the existing ice. The continuous machine may have elastomer wipers between the watery and cooling zones.

Elastomer moulds, especially silicone, ease the removal. The conveyor belt may perhaps be a continuous elastomer, preferably reinforced with fibres over a small thickness; or be thin continuous metal, preferably covered with nickel with embedded Pfte; or have joints.

Stereolithography may help manufacture the head. A (disk) saw would cut the blocks more precisely than the sketched guillotine. Real-time local thickness measurement and feedback looks useful.

Marc Schaefer, aka Enthalpy

[Sensei]

Why not use laser cooling to freeze water?

It can be direct, or indirect.

In indirect method, use f.e. helium with well known wavelength of photons, take energy from helium,

helium atoms will take energy from metal box where it's stored,

and metal box will take energy from environment.

In our case, water.

Another idea is utilizing Mpemba effect
http://en.wikipedia.org/wiki/Mpemba_effect

[swansont]

Why not use laser cooling to freeze water?

 

Laser cooling generally works on atoms, not molecules, and typically involves billions of atoms, not macroscopic amounts.

[npts2020]

Sensei; Swansont beat me to it but would add that lasers are also used for tiny amounts of a substance so that one of the recent big breakthroughs has been cooling something the size of a microchip. Also, I get the impression that it is not a particularly efficient method of cooling but I couldn't find any stats about it from doing a cursory search.