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Q: Does opening a refrigerator cool down the room?

Physicist: Briefly yes, or no, not at all. If you think of the room as including the inside of the refrigerator, then opening the door does nothing. Otherwise, it does almost nothing. But ultimately, if you leave the door open the only end result will be spoiled food.

It seems like it makes sense to say that things like refrigerators and air conditioners “make cold”, but like every other machine ever created (or ever to be created) they ultimately just make heat. A refrigerator “creates cold” in very much the same way that a drain “creates lack-of-water”; it moves heat from its inside to its outside. Specifically, it pulls heat out of the freezer, and drops it into the coils on the back side. (It’s worth noting that about the worst possible place to put cooling coils is in a tiny gap next to a wall).

It’s a general thermodynamic fact (a law even!) that generating cold is impossible. You can generate heat, and you can move it around by taking advantage of the fact that heat always tries to “even out” (this is the idea behind all “cooling devices”), but that’s pretty much it. So just like any other machine, refrigerators generate heat. When you first open the door you’ll get a burst of cold air, but that’s about it. An open fridge is like a water pump in the middle of the ocean, pointlessly moving stuff around. It’ll cool the room a little, but also heat it up a lot more.

A clever thing to do would be to put the heating coils outside of the room. The room would get cooler, the outside would get warmer (slightly), and you’d have re-invented air-conditioning.

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