How Do Refrigerators Work?

The refrigerator is a standard appliance seen in just about every kitchen in the United States. They are a great invention that prevents food from spoiling, thus allowing us to keep food longer, saving us money, and without the waste of any leftovers. Before refrigerators, food expired far more rapidly and the only way to preserve anything was to either can it in a jar or salt it. When refrigerators became available they changed people’s lifestyles completely.

There are many different styles and brands of refrigerators on the market today. The technology has changed slightly from those early models but the basic principles are still the same. It’s all basic physics, really. Refrigerators use the evaporation of liquid to provide cooling. It sounds simple. But how do refrigerators work?

Old Refrigerators vs New Refrigerators

How do old refrigerators vs new refrigerators compare? First, old refrigerators used a chemical gas called Freon. An electric pump sent the Freon through a series of coil tubes. Freon was used to cool the refrigerator but the gas is harmful to the environment. Freon is a brand name for the gas which is actually cholo-floro-carbon (or CFC). Old refrigerators tended to leak CFC which created several problems such as air pollution and health issues in people.

how-refrigerators-workIn the old refrigeration system, CFC started out as a liquid. The refrigerator’s pump pushed the CFC through a series of coils at the top of the freezer. The liquid turned into a vapor which then soaked up some of the heat in the freezer. As it did this, the coils got colder, thus causing the freezer to get colder. Down in the larger refrigerator space, there are smaller coils so the area did not get as cold. Once it cooled things down, the CFC got pumped through smaller tubes on the outside of the refrigerator and got turned back into a liquid. Once it turned back into a liquid, the process started all over again.

Once it was discovered that CFC is harmful to the atmosphere and people, refrigerators gradually changed to a new gas called tetraflouroethane, which changes from a gas into a liquid when cooled. It is much safer on the environment as it does not cause ozone depletion.

Parts of a Refrigerator

There several different parts of a refrigerator required for its operation, all of which perform individual functions. The basic parts of a refrigerator are the compressor, heat-transfer pipes, thermal expansion valve, and the refrigerant.

  • Compressor – The compressor is a unit inside your refrigerator that is powered by an electric motor. The compressor acts to compress the refrigerant gas to a much higher pressure by forcing it into a smaller space, such as tubes. When gas compresses, heat is released. Having a refrigerator with an energy efficient compressor will you lower your electric bill.
  • Heat-transfer pipers – These are a series of pipes behidn the refrigerator that the refrigerant gas is pumped through.
  • Thermal expansion valave – A valve with a small opening that allows the refrigerant to expand, thus cooling off drastically.
  • Refrigerant – This is the chemical gas that refrigerators use. Also known as tetrafluoroethane, this is a common refrigerant that turns into a liquid as it cools.

How All The Parts Work Together

Refrigerators work because of physics. The Second Law of Thermodynamics states that if a cold object is placed next to a hot object, the cold object will become warmer and the hot object will become cooler. How this applies to refrigerators is that the food items original temperature is not lowered. Instead, the evaporating gas draw heat away which leaves the space around the items colder. It is the same methods as an air conditioner.

A refrigerator is divided into two separate spaces; one for freezing (which sometimes includes an ice maker)and the other for refrigeration at a slightly higher temperature. The heat-exchange pipes surround these separate spaces. The compressor, located at the bottom of the refrigerator, pumps the refrigerant gas through the series of heat-exchange pipes.  Smaller refrigerators use tetrafluoroethane while larger, commercial refrigerators use pure ammonia. This refrigeration system is completely enclosed so all of the gas gets recycles and used repeatedly.

The refrigerant gets compressed until it becomes very hot from the increased pressure. The heated gas flows through the coils that are behind the refrigerator. This lets the excess heat to be released into the outside air. This is why your refrigerator feels warm underneath and behind. When the refrigerant cools down it turns into a liquid. The refrigerant is then forced through the small opening on the expansion valve. It works much like a spray nozzle on a hose. By closing the opening, you create pressure. This causes the refrigerant to move quickly and turn very cold as it gets pumped through the rest of the coils. As the refrigerant moves to the coils surrounding the larger compartment inside a refrigerator, the Second Law of Thermodynamics takes effect. That law states that cold materials tend to take heat from warmer materials. Since the coils around the lower compartment are not as dense as the freezer section, they take on more heat. This is why the lower compartment is not as cold as the freezer. As the refrigerant passes through the system of coils, it finally gets drawn back into the compressor and the cycle starts all over.

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