How does a fridge work?

Question

I read the wikipedia page and asked my dad – but I am honest: I don’t understand it.

In: Engineering

Answer 1

(EDIT: u/nullrecord and u/KnowingestJD both have excellent and concise answers, but I’ll be damned if I typed all this just to delete it now!)

Wiki’s not always the best for introducing science and technology–[Here’s a nice page on it.](https://www.scienceabc.com/innovation/how-does-a-refrigerator-work-working-principle.html)

As others have said, the main trick behind it is to run something (the “refrigerant”) through coils of metal pipes that snake between the inside of the refrigerator and the outside, in a loop.

If you think of temperature as heat energy, the more space a given amount of energy is distributed in, the less concentrated it will be at any given point, so a widely-spread cloud of gas will be “cooler” that if it was densely packed.

Refrigerators have a device that expands the “refrigerant” gas travelling through the pipes just before sending it inside the refrigerator so that this gas becomes colder than the air within the fridge, and the heat-conducting metal pipes will naturally allow heat to flow through them from the warmer outside of the pipe (the refrigerator box) to the inside of the pipe (the gas that was just expanded in order to cool it enough to make this work) as the refrigerant passes through.

Having leached heat energy from the surrounding air in the refrigerator, the now warmer gas continues through the pipes until it reaches another device just before leaving the inside of the refrigerator box, and this device compresses the gas until it is hotter than the room-temperature air in your kitchen. Then it goes through another set of coils on the outside, only this time the now-hotter gas is bleeding head outwards to the cooler surrounding air rather than taking it in. Once it loses that unwanted heat, it returns back to the starting point where it is expanded again, and starts over.

It’s the air-pumping to expand and compress the gas that makes them such energy hogs; the refrigerant itself is naturally inclined to flow in the direction desired within the two coils: hotter gas naturally moves upwards, and cooler gas/vapor will sink downwards, so if you put the expander device at the bottom of the fridge and the compressor device at the top, the refrigerant itself is already inclined to move in the direction you want in both the inside and outside coils.