Gemini on Question 7, Sep 19

A refrigerator keeps things cold not by creating cold air, but by continuously absorbing heat from its interior and releasing it into the surrounding room. It achieves this using a closed system of coiled copper tubes filled with a special fluid called a refrigerant, which constantly changes between a liquid and a gas.

The cycle begins inside the appliance, where cold, low-pressure liquid refrigerant flows through the evaporator coils. As the relatively warmer air inside the refrigerator circulates over these coils, the liquid refrigerant absorbs the heat from the air. This heat transfer causes the liquid to boil and evaporate into a low-pressure gas, leaving the inside of the refrigerator cooled.

Having collected the heat, this gas is drawn out of the interior and into a motorized pump called the compressor, which is usually located at the bottom of the machine. The compressor squeezes the gas, which dramatically increases both its pressure and its temperature. Now a very hot, high-pressure gas, the refrigerant is pushed into the condenser coils located on the outside of the refrigerator, typically on the back or underneath.

Because the pressurized gas in these exterior coils is now hotter than the ambient air in your kitchen, the heat naturally flows out of the gas and into the room. As the gas sheds its heat, it cools down enough to condense back into a high-pressure liquid.

This warm liquid refrigerant is then forced through a tiny, restrictive opening known as an expansion valve or capillary tube. Pushing the fluid through this narrow bottleneck causes a sudden and massive drop in pressure. In physics, a rapid drop in pressure results in a rapid drop in temperature, so the liquid becomes intensely cold. This newly chilled, low-pressure liquid flows right back into the indoor evaporator coils, and the entire continuous cycle begins all over again.