Conventional cooling systems like air conditioners and air-to-water heat exchangers rely on chemical refrigerants or water to cool, or remove heat from, enclosures. In addition to refrigerants, air conditioners use compressors, evaporators, condensers and fans to provide cooling.
An air conditioner works by compressing (with the compressor) the vaporized refrigerant -- making it a high-pressure, high-temperature gas. The refrigerant then moves to the condenser where a fan blows ambient air across the condenser coil, removing the heat from the refrigerant, transferring it to the surrounding environment and returning the refrigerant to a liquid state.
At this point, the refrigerant passes through an expansion valve where, like the name implies, it is expanded and evaporated before passing into the evaporator coil. Here, air from inside the enclosure is blown across the coil by another fan, transferring the heat from installed components to the refrigerant.
Then, the vaporized refrigerant returns to the compressor where the process is repeated. Air conditioners can either be mounted on the roof or sidewall of an enclosure, but the units themselves must remain upright to ensure proper functionality. Air-to-water heat exchangers operate by removing the heat from inside an enclosure using cooled water that is supplied by a facility's chiller and channeled through an internal coil.
Within the heat exchanger, a fan blows the heated enclosure air across the coil, transferring the heat to the water. The water absorbs the heat energy and carries it away to the chiller (basically a remote air conditioner used to cool water) where it is cooled again before the process repeats. Air- to-water heat exchangers can also be either roof or wall-mounted, but must have a connection to the facility's chilled water system.
Other than a fan, thermoelectric coolers do not need any of the things required by air conditioners and air-to-water heat exchangers to effectively cool industrial enclosures. The aforementioned Peltier Effect allows thermoelectric coolers to provide cooling without refrigerants, water or components such as compressors and coils.
A typical thermoelectric cooler contains a " Peltier element", a fan, and a power supply. Peltier elements are constructed of 2 bonded semiconductors, often consisting of bismuth doped with telluride and copper. The semiconductors used in Peltier elements are referred to as "N-type" and "P-type" . An N- type semiconductor has an overabundance of electrons and the P-type semiconductor lacks a full set of electrons. This electron deficiency creates "holes" in the P-type semiconductor's molecular structure that are ready to accept the extra electrons moving over from the N- type semiconductor.
These electrons move when the electric current from the power supply is passed through the semiconductor, carrying heat with them and leaving behind a cool surface. The fan then blows across this cooled surface and circulates cooled air throughout the enclosure.
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