The refrigerator was invented by Jacob Perkins in 1830 and has undergone many changes since then, such as the adoption of freon in the 1930s and its subsequent decline in the 1990s. However the main working parts of any refrigerator have not changed significantly and are basically the same in any unit. Refrigerators function similarly to air conditioners, but instead of releasing cool air into a living space refrigerators contain it in an insulated box to maintain a cold temperature for keeping food and other things.
An essential part of any refrigerator, refrigerant begins as a gas, changes to a liquid and then becomes gas again as it flows through all the refrigerator's internal parts. In the early days of the refrigerator, highly toxic gases such as ammonia were used as refrigerant until freon came along in the 1930s. Freon was the primary refrigerant used in the United States until scientists discovered that widespread use of the chemical was harming to the ozone layer. Today most refrigerators use a refrigerant compound known as HFC-134a.
The compressor is located at the bottom back end of the refrigerator. Driven by an electric motor, this energy-consuming mechanism increases the temperature and pressure of the refrigerant gas, then passes the superheated vapor along to the condenser.
Located on the back of the refrigerator, the condenser is recognizable by its large slithering copper coils. The hot refrigerant vapor enters the condenser where it is cooled down by the atmospheric air in the room. At this point the refrigerant liquefies.
The expansion valve, sometimes referred to as the capillary tube in domestic refrigerators, is a set of thin copper tubes much like the condenser. Here the liquid refrigerant passes through as its temperature and pressure slowly drop. The decrease in pressure causes approximately half of liquid the refrigerant to evaporate. This process allows the refrigerant to absorb heat, thus decreasing the internal temperature of the refrigerator.
The evaporator is made of copper and aluminum tubing. Here the remaining liquid refrigerant absorbs heat until it evaporates again into a vapor. The compressor then sucks the vapor out of the evaporator and the refrigeration cycle repeats itself.