Gemini on Question 7, Sep 12

A refrigerator functions not by creating cold, but by absorbing heat from its interior and expelling it to the surrounding environment. This continuous process of heat transfer relies on a chemical compound called a refrigerant, which constantly changes between a liquid and a gaseous state as it travels through a closed system of copper and aluminum tubes.

The cycle is driven by the compressor, a motorized pump located at the bottom or back of the appliance. The compressor squeezes the low-pressure refrigerant gas, which significantly increases its temperature and pressure. This hot, highly pressurized gas is then pushed into the condenser coils, which are typically found on the exterior of the refrigerator. As the hot gas flows through these exterior coils, it releases its thermal energy into the ambient air of your kitchen. Losing this heat causes the refrigerant to condense into a high-pressure liquid.

This liquid then travels toward the interior of the refrigerator and passes through an expansion valve, which acts as a very narrow bottleneck. Forcing the liquid through this tiny opening causes a rapid and massive drop in pressure. Much like an aerosol spray can feels cold when you release the contents, the refrigerant experiences a sharp drop in temperature as it expands, turning into a remarkably cold mixture of liquid and vapor.

This freezing mixture flows directly into the evaporator coils located inside the insulated refrigerator compartment. As the cold refrigerant travels through these interior coils, it absorbs heat from the food and air inside the fridge. Removing this heat is what drops the internal temperature and keeps your groceries cold. The absorbed heat causes the refrigerant to boil and completely vaporize back into a low-pressure gas. Finally, this warm gas is drawn back down into the compressor, and the entire continuous cycle begins all over again.