And shouldn’t it be a power generator
In: Physics
Have you ever taken a can of compressed air and just held it down to shoot air for a while? You will find when you do this that the can gets very cold. You might even see Frost develop. What’s happening is a very compressed Gas is being allowed to escape the can and expand freely all at once. The technical term for this kind of expansion is ‘adiabatic’ but it just basically means that the gas is allowed to expand back to its full volume before it has time to slowly absorb heat from the environment. The result is that you formerly had a very small volume of compressed gas at room temperature, and after the expansion you now have the same amount of heat energy that was in that small volume spread out into a much bigger volume. This results in it having a lower temperature.
The whole process described here so far doesn’t really cost energy aside from the small amount used to open the valve. But in order to get that very compressed room temperature air, you have to use a pump to compress a gas into a very small hot lump, and allow that to cool itself off down to the temperature of the ambient air. If the heat from that lump was allowed to come back into the original room where it was compressed, air conditioners wouldn’t work, because the amount of heat created by compressing is more then the amount of cooling you get by letting the gas expand back to its previous volume. This is largely because the compression process is imperfect (friction on the piston, etc). So the refrigerator or air conditioner really works because it’s moving heat from one place to another. That’s why air conditioners are put in windows – to vent that heat – and part of the reason why refrigerators are so well insulated.
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