Presented By:-
Harsh Jha

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Cryogenic Refrigeration (Freezing )
INTRODUCTION
Cryogenics may be defined as the branch of physics which deals with the production of very low temperature and their effect on matter.
It may also be defined as the science and technology of temperatures below 120K.
The word “cryo” is derived from a Greek word “kruos” which means cold.
Cryogenics use the absolute temperature scales. These are Kelvin(SI units) or Rankine scale  (English/US units)
Methods To Produce low Temperatures
The most recent development in cryogenics is the use of magnets as regenerators as well as refrigerators.
By compressing the gas using a stirling cryocooler.
The ideal series of steps :-
First step.
Second step.
Third step.
Fourth step
Cryogenic cooling of devices and material is usually achieved via the use of a cryocompressor (which uses high pressure helium lines).  
Cryogenics In Fuels
Fluids are stored at 93.5k(-180 degrees) or below.
Due to air friction , it gets ignited.
Cools engine on expansion.
On expansion pressure increases providing high thrust.
Satellite payload increases.
Cryogenic Rocket Engines
Cryogenic rocket engines are one of the important applications in the field of cryogenics.
Cryogenic Heat Treatment
Treating metals, plastics, ceramics at temperatures below 120K to their crystal structures and properties.
This increases the wear resistance.
They are used in the field of super conductors.
Permanent coating is completely imparted to the metal surface.
Comparative microphotographs (1000x) of steel samples show the change in microstructure.
The number of countable carbides increases from 30,000 to 80,000 per square millimeter which forms a “super hard” surface on the metal.
In this process the alloy steels are treated to covert the entire austenite into a martensite matrix.
Advantages of Cryogenic processing
Increases wear resistance
Increases corrosion resistance
Good dimensionality
High strength
Good quality and surface finish
Cost reduction in material manufactured
Lower stress corrosion
Reduce the stored stress
Applications of cyrogenics
Commercial transportation of liquefied natural gas.
Without cryogenics, nuclear research would lack liquid hydrogen and helium for use in particle detectors and for the powerful electromagnets required in large particle accelerators.
Electromagnets are also being used in nuclear fusion research.
Cryogenic particle detectors are radiation sensors that operate at very low temperature, typically only a few degrees above absolute zero.
Cryogenic cooling is often used in space telescopes that observe objects in infrared and microwave wavelengths.
Cryomicrobiology.
Cryogenic metal treatment process.
Cryogenics In Biology
Cryogenics used in artificial insemination to store semens and embryos.
Cryosurgery is a surgical technique in which freezing is used to destroy undesirable tissues.
Liquid nitrogen, which boils at -196 degrees, is the most effective cryogen for clinical use.
Temperatures of -25 to -50 degrees can be achieved within 30 seconds if a sufficient amount of liquid nitrogen is applied by spray or probe.
Other applications of cryogenics
Magnetic resonance imaging (MRI).
Electric power transmission.
Frozen food.
Blood banking.
Cryo microbiology.
Future of Cryogenics
Cryogenic rocket engine which will be used by NASA for its next manned moon mission.
CONCLUSION
Finds its application in metal treatment processes to a large extent.
Applicable in the field of ‘Biotechnology’.
Applicable in space research programs.
Good future prospects as it still is a growing field.
This process is ‘Eco-friendly’.