I must be missing something...

[EliteRetard]

If you compress a gas into a liquid it gets very cold. If you dont let the gas expand it will stay very cold. So if you could put a cold liquid gas in a tube and permanently seal it the tube would always be cold right? But how does that work...put the tube in a room and the room would eventually have to get cold right? How is it cooling without using any energy? Theoretically, could something like this be used to cool a hot component like an engine or a processor? Obviously some liquid gas' requires huge pressures...but what about weaker stuff like liquid carbon dioxide?

 

[CycloWizard]

The answer is simply no - you can't cool a room indefinitely by putting a tube of cold liquid in it. The liquid's temperature will rise as it cools the room. Heat transfer occurs when energy from the hot room is transferred to the cold liquid. The end result is that the cold liquid warms up and the room cools down. The relative thermal masses (mass times heat capacity) of the liquid and air determine the extent to which the cold liquid can cool the room. If you had a cold liquid with "infinite" heat capacity, it could cool the room down to the same temperature as the liquid itself.

 

[Hacp]

If you compress a gas into a liquid it gets very cold. If you dont let the gas expand it will stay very cold. So if you could put a cold liquid gas in a tube and permanently seal it the tube would always be cold right? But how does that work...put the tube in a room and the room would eventually have to get cold right? How is it cooling without using any energy? Theoretically, could something like this be used to cool a hot component like an engine or a processor? Obviously some liquid gas' requires huge pressures...but what about weaker stuff like liquid carbon dioxide?

A liquid is a liquid. If you put it in a container and leave it in a warm room, the liquid will become warm.

 

[CTho9305]

If you compress a gas, it actually gets very hot. The heat then radiates away, and you end up with a room temperature liquid. When you start letting the liquid evaporate, that's when it becomes very cold. Note that some gases won't become liquid at any pressure above a certain temperature, so if you really want a liquid you have to actively cool it down. Check out This video for an example.

 

[Ninjahedge]

CT said it.

Think of it like kenetic energy (which it is on an atomic scale). You take a bunch of atoms in a gas and compress them, they get HOT. That heat can radiate out to equilibrium with the surrounding environment. When you decompress, you get this lower energy compressed gas to lose even more energy (in the expulsion of the gas itself, as well as decompressing and having fewer collisions, I believe, on the containment surface).

It cools down. Go and find a set of Nitrogen tanks they use for somethings (like cleaning and construction). Once they have been used (or leaking) for a while, they will develop frost. This is not because they WERE cold, but they are GETTING cold.

Same thing with the compressed air cans you get.


Now, as for liquids? That is an even LOWER energy state. You only get gasses to become liquids by either compressing them so that their own volitility is not enough to allow them to escape (the external pressure plust their own attraction to each other keeps them in liquid form) or dropping their temp and reducing their thermal energy/velocity to below "escape" velocity (boiling).

A gas that is a liquid is only cold at atmospheric temp when it has been cooled first.....

I hope you have it clear! It's important to know the basics of some of this stuff like it was the alphabet. It makes other things much easier to "see" when studying more advanced topics.....

 

[Murloc]

you have a conceptual problem. During the forced compression or expansion (by changing the geometry of the container) in a ideal thermally sealed environment the substance changes temperature, but if you put it anywhere it cools and warms like any other stuff.
I did it 2 years ago in high school, I'll try to remember.
It's just that temperature is given by the kinetic energy of the molecules, and you get the temperature because you feel them bouncing on you.
If you compress them, the same energy will be in a smaller place, thus increasing the temperature, but the energy contained is the same.
If it exchanges energy with the room it will get warmer, and the room will cool down until an equilibrium has been reached.
Hope I got it right.

 

[KIAman]

CT is right on the money.

If you compress a gas into a liquid it gets very cold.

Nope, it actually gets hot (if it got cold while compressing, we would all enjoy free AC but would have to rely on electric filament or fuel burn for heat).

So if you could put a cold liquid gas in a tube and permanently seal it the tube would always be cold right?

Assuming the seal is perfect and can maintain infinite pressure, nope. The liquid temperature will equilize with the environment (in a room, aka room temp).

But how does that work...put the tube in a room and the room would eventually have to get cold right? How is it cooling without using any energy? Theoretically, could something like this be used to cool a hot component like an engine or a processor? Obviously some liquid gas' requires huge pressures...but what about weaker stuff like liquid carbon dioxide?

Because of your first 2 initial assumptions were wrong, the rest of your statement which relies on your assumptions are also wrong.

 

[EliteRetard]

YAY, I LEARNED SOMETHING!

But it wrote over the memory of where my keys are...and something else I know I forgot.

 

[Paul98]

Are you talking about certain elements such as hydrogen or helium where you need both high pressure and low temperature to get them to change from gas to a liquid? If you don't have one or the other it's not going to be in liquid form. Why did you think it would stay cold even if put in a normal room?