There is a reason why refrigerator evaporator coils are frosted over. These coils are made up of two or more layers of liquid metal, which are immersed in liquid refrigerant (that is, an electrically charged gas) in order to maintain a constant temperature within the refrigerator. This liquid refrigerant also contains a number of other chemicals that help keep ice cubes from forming in the refrigerator. If you were to see the refrigerant sitting in front of your refrigerator, it would be almost as cool as if it were sitting on top of the coils themselves. The liquid refrigerant that actually flows through the refrigerant lines is often referred to as “aqueous refrigerant,” and is composed of water and hydrogen gas. The refrigerant gas flows through a series of small tubes, which in turn feed a main line, which carries a cooling fan that keeps the refrigerant gas at a proper, safe temperature. In the case of refrigerators with evaporator coils made from a certain material, this cooling fan can be set to turn on only when the liquid refrigerant reaches a certain temperature.
While the liquid refrigerant can cool the refrigerant gases in refrigerators, the refrigerant gas itself will not freeze until it reaches a lower temperature than the liquid refrigerant. This means that the temperature of the refrigerant gases is always slightly above the freezing point, since they are constantly changing temperatures. When the refrigerant gas does reach the appropriate temperature, it then forms a layer of frost on the coils, which prevents the refrigerant gas from forming any ice particles in the refrigerator. Because the liquid refrigerant itself is never actually frozen, it can still remain within the refrigerator, without any frost forming. While this is very important, it is actually the layer of frost that is responsible for keeping ice from forming inside the refrigerator.