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[noodle0117]

A physics question just popped in my head.

How exactly does a freezer/refrigerator/cooler work?
In order to lower the temperature of an object, you'll need another object that's at a cooler temperature to take away heat. Now this works out fine and dandily when I think about trying to cool down hot objects such as recently cooked food and running engines, but how does it work when trying to cool down already cold objects?

In order to cool something down (lets say a bag of peas in a freezer), I need the freezer to be colder than the bag of peas. But in order to get the freezer to become that cold, I'll need something else even colder and so on. So this is where my brain hits a dead end since I'm not sure how anything can get cooled down to below room temperature without something colder than everything else in the first place.

Yet science makes it happen.

Pretty sure my mental physics simulator is missing something, but how do refrigerators work then?

[Frumple]

Yeah... not 100% sure of the whole thing myself, but I think where your cognihiccup is occurring is with the "must have something colder" bit. You don't need something colder, per se, you just need a way to get the heat somewhere else, s'far as I'm aware. And we've got fancy ways of doing that, yeah. Wikipedia sometimes helps. Hopefully someone a bit more familiar with stuff can plain-language translate it a bit better.

[Canisaur]

http://en.wikipedia.org/wiki/Refrigeration#Vapor-compression_cycle

The compressor uses electricity to force the freon to condense, and when it expands again in the evaporator it absorbs heat (the expansion is endothermic, same reason why water evaporating from your skin makes you feel cold), making it cold (colder than the contents of your fridge/freezer).  Then it simply blows air over the cold coils in the evaporator, moving the 'coldness' into your fridge/freezer.

[Neonivek]

It is also why fridges aren't bad for the environment so long as you don't do what Duke Nukem did and intentionally break them all at once.

Yes... Captain Planet has a villain named Duke Nukem... He even wears a Hawaiian T-shirt just like Duke Nukem.

[MonkeyHead]

It helps to think of the inside of the fridge as having less internal energy (i.e. heat) than the surroundings. All the fridge is in actuality is a method of carrying heat energy away from someplace, leaving it with less internal energy (less heat) and hence a lower temperature. This takes a signifigant expenditure of energy (work) to manage though. Dont think of it as moving coldness, as cold is a privative - it doesnt exists as a "thing", only as the absence of heat.

[Lectorog]

Guys. Cold air is piped down from northern Canada. 's why most people in Mexico and Central America can't afford refrigeration.

[Sergius]

This is how I understand it:

When a gas compresses, it heats up. When it expands, it cools down.

So, basically you pump a gas (freon) from a wide pipe into a narrow pipe, so it compresses and heats up. Then it keeps going around some coils where it dissipates the heat (going to room temperature, or so), then you let it expand again at the other end, so it cools down, but since it was at room temperature, it gets really cold.

Then you use it to cool down your fridge, and it ends at room temp again. Repeat..

[Jelle]

T=PV/nR
T= temperature
P= pressure
V= volume
n= amount of molecules
R= gas constant

Increase pressure on coolant (till it condenses?), heats up, exchanges heat to environment. Expose cooled pressurized coolant to refridgerator, release pressure, coolant absorbs heat from environment and makes the interior colder.

Same principle as when you puncture a can with condensed gas, the can will normally cool down dramatically due to all those molecules absorbing that energy as they expand.

Is how I think it worked anyway, bit rusty on the sciency stuff.