Physical principle (Peltier effect)on which the thermoelectric cooling is based, has been known since 1834, Thermoelectric cooling transfer heat energy from one place to another with the help of electrons, not refrigerants. Figure 3-17A represents a simple thermocouple. The pair moves heat from the inside of the insulated space heat exchanger. The heat exchanger is on the outside. Electrons, not refrigerants, carry away heat. Edges of the evaporator (dark blue) increase in the heat flow. Fins on the outside of the heat exchanger (dark red) to help give heat to the surrounding air.
Semiconductors are materials that conduct electricity, but not as good as typical metals. They can be made of elements such as silicon, germanium, or a combination of elements. Semiconductors can be processed in such a way that N-type semiconductors electricity flow of negatively charged particles (electrons). The other, called the P-type semiconductors, conduct electricity flux of positively charged particles (often called a "hole" (or electron-hole).
Figure 3-17A shows the current is forced to flow from P-type to N-type material material.
The junction where N and P are associated absorbs heat. The opposite ends of the heat and to give warmth. This is the Peltier effect. One junction is producing only a small cooling effect. Therefore, several N-P paired intersections are connected in series to produce significant cooling. Fig. 3-17B. A group of modules can be connected in parallel to increase the power even further. (Chapter 6 for a series-parallel connection.)
Thermostat inside the refrigerated space controls the current flow through the transformer-rectifier. Transformer rectifier supplies a controlled DC modules. Thus, the temperature inside the refrigerator is under control.
The absence of moving parts in thermoelectric cooling. Besides the construction of the modules, it is quite simple. Thermal efficiency is low. Volume of the refrigerating effect generated electrical energy spent is less, than with standard compressors type of refrigeration system. By changing the direction of the flow of current through a thermoelectric device turns hot and cold surface. Thus, the device can be used for heating and cooling isolated space. Thermoelectric device used in air conditioning and heating nuclear submarines. Thermoelectric devices are often used for temperature control of electronic equipment such as computers, aerospace instruments and other).
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