It feels like we’re breaking some laws of thermodynamics in that article.
The salts dark color draws in heat to melt ice? Also salt isn’t dark afaik.
How does this thing actually work?
The salts dark color draws in heat to melt ice? Also salt isn’t dark afaik.
How does this thing actually work?
The refrigeration cycle works by adding a salt (NaI, or sodium iodide to an ionic solvent, ethylene carbonate). This lowers the melting point of the salt below the temperature of the solvent, and the salt consequently absorbs heat from the solvent in order to overcome it energy of fusion, thus cooling the solvent. The the resulting temperature deficit relative to the environment can be transferred thermally to a cold reservoir. Subsequently, they use electro-dialysis to remove the salt from the "used" solvent, and recrystalize the salt, yielding fresh solvent and salt so the cycle can be repeated.
Relative to what happens with road salt, the salt in the refrigerator is playing the role of the road ice, and the solvent is playing the role of the liquid water with dissolved sodium chloride that forms on the ice when you salt the road. The reason that water forms is because the road salt, which is relatively dark due to impurities, absorbs solar energy melting a thin layer of water, or tire friction on the salt-ice combination does so, or because there is slushy liquid water already present.
Going from liquid to solid do not generally causes any changes in volume, but it does releases some energy as part of the conversion process, which if captured could contribute to make both the solid and liquid cooler (less energy among the molecules in the same volume).
With the use of a compressor and a vapor chamber in a fridge you can control when and where the liquid turn to a gas or back into a liquid. The hot place will be near a radiator, and the cold place in a vapor chamber next to the cooling area. With this system the salt would be near the radiator turning the solid into a liquid, heating the radiator. Then you would "remove the salt" in what would be similar to a vapor chamber, turning the medium cold.
The biggest issue I have with this concept is the efficiency. With a compressor you can make a gas really really hot by turning it into a liquid, and that heat will then have a large gradient difference when run through a radiator (which cools it down using ambient air). I am unsure how one would get a similar effect with solid to liquid.
Yeah, they're flat wrong on that claim. Science figured this one out long ago. You could throw white salt on white snow and it'll still cause it to start melting.
This refrigerator appears to use a similar premise of adding salt to (ethylene carbonate in this case) in order to drive an endothermic reaction and draw heat in from the environment. In order to remove the salt to reuse the loop, they are using electrodialysis, so thermodynamics is preserved - that's where energy goes into the system.
As I recall, ice has a thin layer on top that mixes with a little of the salt, which lowers the freezing temperature, causing more melting, and so on. You can throw white salt on white snow and it'll still work.
So apparently it uses the same amount of energy, so no breaking of thermodynamics.
And yeah salt is white or clear, dunno what's up with that statement.
"When water is mixed with salt the freezing temperature of the solution is lower than 32 F. The salt impedes the ability of the water molecules to form solid ice crystals. It’s important to note that the salt must be in a solution with liquid water in order for this principle to be obeyed. Salt that’s dumped on top of ice relies on the sun or the friction of car tires driving over it to initially melt the ice to a slush that can mix with the salt and then won’t refreeze."
https://www.scientificamerican.com/article/salt-doesnt-melt-...
Table salt, no - manganese dioxide, yes.