There are always more than one inventors, or should I say, contributors to an invention and the refrigerator is not an exception.  At the University of Glasgon in 1748, William Cullen came up with the first known artificial refrigeration.  However, his great discovery was not put in any real objective.  Oliver Evans made the first actual refrigeration machine in 1805.  Out of all these, Jacob Perkins, an American inventor obtained the patent for the first refrigerating machine in 1834 by using a vapor compression cycle.  Of course, things often get modified.  In 1850, Edmond Carre developed the first absorption machine by water and sulphuric acid.  Ferdinand Carre, Edmond's brother, introduced the first ammonia/water refrigeration machine in 1859.  Any new inventions would have cost a lot back then.  What helped reduced the cost was the designs of the refrigerators included latching doors were replaced with magnets placing in the seals.

So how does it really work?

The Refrigeration Cycle
The refrigerator in your kitchen uses a cycle that is similar to the one described in the previous section. But in your refrigerator, the cycle is continuous. In the following example, we will assume that the refrigerant being used is pure ammonia, which boils at -27 degrees F. This is what happens to keep the refrigerator cool:


  1. The compressor compresses the ammonia gas. The compressed gas heats up as it is pressurized (orange).
  2. The coils on the back of the refrigerator let the hot ammonia gas dissipate its heat. The ammonia gas condenses into ammonia liquid (dark blue) at high pressure.
  3. The high-pressure ammonia liquid flows through the expansion valve.

    You can think of the expansion valve as a small hole. On one side of the hole is high-pressure ammonia liquid. On the other side of the hole is a low-pressure area (because the compressor is sucking gas out of that side).

  4. The liquid ammonia immediately boils and vaporizes (light blue), its temperature dropping to -27 F. This makes the inside of the refrigerator cold.
  5. The cold ammonia gas is sucked up by the compressor, and the cycle repeats.

Pure ammonia gas is highly toxic to people and would pose a threat if the refrigerator were to leak, so all home refrigerators don't use pure ammonia. You may have heard of refrigerants know as CFCs (chlorofluorocarbons), originally developed by Du Pont in the 1930s as a non-toxic replacement for ammonia. CFC-12 (dichlorodifluoromethane) has about the same boiling point as ammonia. However, CFC-12 is not toxic to humans, so it is safe to use in your kitchen. Many large industrial refrigerators still use ammonia.

 

            --www.howstuffwork.com

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