Refrigerators - Broken thought experiment

Refrigerators - p. 11 - Better explanation needed as to why temperature in the room goes up with fridge door open. The experiment needs to have parameters defined. The explanation would be more clear if it stated why cooling takes more energy than heating. Opening the door has a two-fold effect. It’s adding cooler air causing the room temp to drop in the short term, and eventually causing the pump to run, thus generating more heat in the long term, while still adding cooler air. The cooling process doesn’t stop, just because the external radiator starts releasing heat.

Without knowledge of convection rates for 2 processes, how fast the internal cool radiator is exchanging heat compared to the external radiator, there is no way to answer the question without trial and error guesses of what the experiment’s factors are.

Why is less energy absorbed by the internal radiator then is released by the external radiator?

Why can't we just make the internal radiator bigger to offset the exchange, and keep the temperature equal?

addendum: There is no option to post this under the correct topic: Physics of the Everyday

Note by Dylan Valentine
10 months ago

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Why can't we just make the internal radiator bigger to offset the exchange, and keep the temperature equal?

Hey Dylan. The second law of thermodynamics states that it's impossible to turn energy into work without any loss. In other words, nothing is perfectly efficient.

Perfectly efficient in this case would mean that the refrigerator takes some amount of heat, \(Q,\) out of the refrigerator and dumps it into the room. But it isn't, so it always has to dump this amount of heat plus something extra. No matter what the refrigerator is trying to cool, it always has to put more heat into the room than it removes from what it's cooling.

So when you unleash the refrigerator onto the room itself (by opening the door), the same principle holds. Being not perfectly efficient, it will always create net heat through dissipation.

Josh Silverman Staff - 10 months ago

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