How does a refrigerator work?

In the summertime, have you ever gotten hot enough to sweat, and then felt very cool when the wind blows? This is because the water on your skin is evaporating. The air carries away the water vapor, and with it some of the heat is being taken away from your skin. This is similar to what happens in older refrigerators, except instead of water, refrigerators use chemicals to do the cooling.

If you look at the back or bottom of an older refrigerator (pre-1990s), you will see a tube that loops back and forth. This tube is connected to a pump that is powered by an electric motor. Inside the tube is Freon, a type of gas, chemically called choroflourocarbon (CFC).

CFC starts as a liquid. The pump pushes the CFC through a lot of coils in the freezer area. The chemical then turns into a vapor. When it does, it soaks up some of the heat that may be in the freezer compartment. As it does, the coils get colder, and so the freezer gets colder. For the refrigerator compartment, there are fewer coils in a larger space, so less heat is soaked up and the refrigerator is warmer than the freezer.

After passing through the refrigerator coils, the pump sucks the CFC vapor and forces it through thinner pipes on the outside of the refrigerator. By compressing the vapor, the CFC heats up and expands. The heat given off is absorbed by the air around it. This is why it may be warmer behind or under your refrigerator. Once the CFC passes through the outside coils, the liquid is ready to begin the cycle again.

Modern refrigerators don’t use CFC, because it is harmful to the environment. Tetrafluoroethane (HFC) is used now. The way a modern refrigerator works is similar to an older one. The motor and compressor squeezes the HFC. When it is compressed, a gas heats up and passes through coils on the back or bottom of a modern refrigerator. The warmer gas loses its heat to the air in the room.

As HFC cools, it becomes a liquid that flows through an expansion valve, a tiny hole that the liquid has to squeeze through. A low pressure area is in the coil between the valve and compressor. When HFC flows through this area, it begins to boil and changes into a gas. The coils go through the freezer and refrigerator compartment. The cooler liquid in the coils pulls the heat out of the compartment, making the inside cooler. The compressor sucks up the cold gas, and the gas goes back through the same cycle.