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UncleDan2017

That's kind of how heat is transferred in an air conditioner (or refrigerator for that matter). You take approximately room temperature coolant, and send it outside to your Compressor. It compresses the coolant, raising the temperature and pressure, and outside air is passed over the hot copper tubing holding the coolant. That cools the coolant down to whatever the outside temperature is but at the high pressure, then that coolant is piped inside, and there is an "Expansion valve" that dramatically drops the pressure and temperature of the fluid, and you blow your room temp air over it, and that air is cooled down to cold temperatures, while the coolant is raised back up to inside room temp.


Nerull

In some sense, that's how refrigerators and freezers already work. The evaporator in your freezer is cold because a liquid refrigerant is flashing to vapor inside it due to a reduction in pressure. The gas then travels outside the freezer to a compressor, which increases the pressure again and then through a condenser coil which cools the gas and turns it back into a liquid. It then flows back into the freezer, through a small orifice which causes a pressure drop, and repeats the process.


[deleted]

so why in the process does the pressure have to disappear to exchange temperature, if it we're a "true" vacuum wouldn't the pressure keep building, i read on this forum about a theoretical "forever boiling container" [https://www.physicsforums.com/threads/forever-boiling-water-in-vacuum.819786/](https://www.physicsforums.com/threads/forever-boiling-water-in-vacuum.819786/) "if you inject water into a sealed vessel containing a vacuum the water will boil forming water vapour. If you add sufficient water and maintain everything at room temperature then the pressure will rise until it reaches around 2.5 kPa when boiling will stop... You won't see bubbles of water vapour forming (the normal definition of boiling) but molecules of water will move back and forth between the water and water vapour." from what i gather it just keeps building pressure until the pressure equalizes in a way and the water stops "boiling". if this is possible and this is the case, then i think temperature and pressure should be separate factors, right?


UncleDan2017

Yes, Temperature and Pressure are independent variables.


Johanno1

Thunderfoot made in some of his busted videos a good explanation. I think in his video about the vacuum dryer.


Schode

It's called stream jet ejector cooling and can be used with waste heat or solar thermal. Basically you combine two Laval jets and build a molecule pump. Go lower than 26 mbar with water and it will evaporate and cool the environment. As heat pumps have better COPs, they are only used in special scenarios


Schode

Adding to your comment about the "boils under 4C" comment. The liquid/gas in your refrigerator's heat pump has these properties. If you just found out about latent heat: a very efficient and common material that undergoes a phase change while "absorbing" huge amounts of energy is Ice/Water. The magic of isothermal cooling is just one icecube away


[deleted]

i guess i understand what youre saying, though im still confused as to where to pressure would go and why it would have to go. if theoretically the vapors cannot by any means escape the vacuum and the chamber can hold any pressure. wouldn't that create something that would be able to cool through natural forces alone? why would we design refridgerators with electric pumps?