How does a
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
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
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.