Peltier Coolers

Solid State Cooling:

There are still other useful methods of refrigeration. A Peltier cooler can transform electrical energy into that of thermal energy. The Peltier Effect can be explained through electron motion. As current is applied to a peltier cooler, the following occurs:

  • Electrons increase or decrease their velocity based on the contact potential difference of the material they are traveling though.
  • If the electrons speed up in the material, kinetic energy increases and this energy is converted to heat. For the slowdown of electrons, the opposite occurs.

Here is an example of how a peltier cooler works: Cooling is created through the combination of a current source, two pieces of highly conductive wire (like copper), and a piece of bismuth or iron wire. When the conducting wires are connected to the bismuth and the battery, a sever difference in temperatures between the two conducting wires is observed.

The junction where current flows from the conducting wire to the bismuth will be very hot, and the wire from the bismuth to the conducting wire will be very cold. One can now see how this technology may be useful for refrigeration. If the cold side is placed inside the refrigerator, and the hot side is placed on the outside, zonal cooling will take place.

(Courtsey of Peltier Coolers)

The above diagram shows an example of an N-P type, semi-conducting peltier cooler. From p to n junctions, conductivity is high and electrons move quickly. The opposite is the case for n to p junctions). This explains the difference in temperatures of the copper plates. This method can be used to make refrigerators by simply facing the cold end on the side of the refrigerator, and placing the hot end on the outside (Peltier Coolers 1).

Peltiers are also commonly used as cooling devices for computer processors, as they are extremely effective at cooling these units.

(Courtsey of Peltier Coolers)

A common problem with this method of cooling CPUs is the dissipation of the heat produced by the hot side of the peltier. Sometimes even with a heat sink (radiator) and a fan, one still may not be able to dissipate the heat quick enough to make the peltier cooler effective and beneficial.

Now that we know how to cool the inside of a refrigerator through several different means, we will examine how to best retain this lower temperature.

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