Paramagnetic Cooling and Air Cooling Cycle
It is a type of cooling used by researchers to achieve temperatures close to absolute zero temperature. Paramagnetic materials can be simply described as “materials that can not be pulled by the magnet”. When a paramagnetic material is cooled excessively, the heat transfer of its molecules is reduced, as in other materials. In this case, when these substances are introduced into a violent magnetic field, it is seen that the paramagnetic salt molecules come into a state of elementary magnetism. When the magnetic field applied to this material is removed, the paramagnetic salt temperature falls excessively because it is not heat exchange. It is possible to reach temperatures of 0,001 K by experiments done in this way. This phenomenon can be likened to a compression cycle at the molecular level. This process causes severe magnetic field compression and the molecular heat is taken up by the surrounding helium and hydrogen . When the magnetic field is lifted, the temperature drops to lower levels, as is the reduction in pressure on the molecules, as is the case with expansion in the vapor compression cycle. The cooling system of paramagnetic material is shown below.
Magnetic chilling of paramagnetic material.
In the course of this cooling process, the paramagnetic metal is pre-cooled with liquid hydrogen and liquid helium, and then the magnetic field is removed with the help of electromagnets to reduce the paramagnetic salt temperature. Investigations of the thermal and electrical conductivities of near-zero temperature values of the materials have applications in the fields of industry, medicine and agriculture.
Air Cooling Cycle
Unlike other refrigeration cycles, in this cycle, the refrigerant always remains gaseous throughout the system, never liquefied. The air cooling cycle operates according to the open system (refrigerant air, taken from the continuous atmosphere and used after cooling down) or closed system principle. In the following principle the expansion cylinder provides both the expansion valve function and part of the compression force necessary for the compressor and thus the power requirement is reduced.
Closed system air cooling system
The application of the air cooling cycle as above is not preferred due to its low efficiency coefficient. Instead, the above scheme is used to air passenger cabin airplanes. The advantages of this system are that the equipment is light and the refrigerant is in the form of gas in the entire cycle.
Application of simple air cycle to jet engine