CRYOGENICS

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CRYOGENICS

• PRESENTED BY
• RAJKUMAR.G
• VASUDAVEN.S

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ABSTRACT

• Cryogenic Treatment is a material science and
  involves the process of reducing the temperature
  of components over an extended period of time to
  extreme cold levels, usually slightly below
  -250C. The use of vapour compression circuit is
  to provide pre-cooling emphasis the dependence of
  cryogenic cooling technology on refrigeration and
  the synergy between the two technologies. It is
  apparent that gas compression and reduction in
  temperature as a result of throttling are common
  to both systems. The differences are the
  thermodynamic properties of the working fluid and
  the temperature range of cycle. The significance
  of critical temperature is also apparent. In the
  vapour compression cycle shows all the processes
  occur below the critical temperature, as it
  typical for such cycles, and therefore
  condensation of the working fluid is possible
  simply by rejecting heat to a sink at a lower
  temperature. By contrast, in the cryogenic cycle
  the temperature of the working fluid only falls
  below the critical value in the throttling
  process. By this method, cryogenic treatment
  helps to reduce the temperature very low.
• Keywords
• Absolute zero, Linde-Hampson system, Claude
  system, various applications.

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INTRODUTION

• Cryogenics stems from Greek and means "the
  production of freezing cold" however the term is
  used today as a synonym for the low-temperature
  state. It is not well-defined at what point on
  the temperature scale refrigeration ends and
  cryogenics begins. Cryogenics typically involves
  a deep-freezing process, usually one that takes
  object down below 240 degrees Fahrenheit and
  changes the molecular alignment of the material
  structure. This change creates the new property.
  Cryogenic process has been researched and
  developed by universities and NASA since the
  mid-sixties after NASA discovered that deep space
  exploration vehicles had improved their
  structural integrity due to extended exposure to
  cryogenic temperature.
• The terms cryogenics, cryobiology are
  frequently confused and given below
• Cryogenics
• The branches of physics and engineering that
  involve the study of very low temperatures, how
  to produce them, and how materials behave at
  those temperatures.
• Cryobiology
• The branch of biology involving the study of
  the effects of low temperatures on organisms
  (most often for the purpose of achieving
  cryopreservation).

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• TYPES OF CRYOGENIC TREATMENT
• SHALLOW CRYOGENICS, made the objects to
  temperature of approximately -120o F.
• FLOODING, takes the component to -120o F, then
  the chamber is flooded with liquid nitrogen.
• DEEP CRYOGENICS TREATMENT, Subjects the objects
  to the temperature of approximately -300o F.
• ABSOLUTE ZERO
• Absolute zero is a temperature marked by a 0
  entropy configuration. It is the coldest
  temperature theoretically possible and cannot be
  reached by artificial or natural means.
  Temperature is an entropically defined quantity
  that effectively determines the number of
  thermodynamically accessible states of a system
  within an energy range. Absolute zero physically
  possesses quantum mechanical zero-point energy.
  Having a limited temperature has several
  thermodynamic consequences for example, at
  absolute zero all molecular motion does not cease
  but does not have enough energy for transference
  to other systems, it is therefore correct to say
  that at 0 Kelvin molecular energy is minimal. In
  addition, any particle with zero energy would
  violate Heisenberg's Uncertainty Principle, which
  states that the location and momentum of a
  particle cannot be known at the same time. A
  particle at absolute zero would be at rest, so
  both its position, and momentum (0), would be
  known simultaneously.
• By international agreement, absolute zero is
  defined as precisely 0 K on the Kelvin scale,
  which is a thermodynamic (absolute) temperature
  scale, and -273.15 on the Celsius scale.1
  Absolute zero is also precisely equivalent to 0 R
  on the Rankine scale (same as Kelvin but measured
  in Fahrenheit intervals), and -459.67 on the
  Fahrenheit scale.

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• PRODUCTION OF LOW TEMPERATURE
• The following methods are involved to produce
  the low temperature in cryogenics
• Heat conduction It is a relatively simple
  concept to understand. When two bodies are in
  contact, heat flows from the body with the higher
  temperature to the body with a lower temperature.
  Conduction can occur between any and all forms of
  matter, whether gas, liquid, or solid. It is
  essential in the production of cryogenic
  temperatures and environments.
• Evaporative cooling Humans are familiar with
  this process because it is a mechanism in which
  our bodies lose heat. Atoms and molecules in the
  gaseous state are moving faster than the atoms
  and molecules in the liquid state. Add heat
  energy to the particles in a liquid and it will
  become gaseous.
• The Joule-Thomson effect It was discovered by
  the English Physicist James Prescott Joule,
  William Thomson and Lord Kelvin, in 1852. They
  found, for example, that allowing a gas to expand
  very rapidly causes its temperature to drop
  dramatically. Reducing the pressure on a gas
  accomplishes the same effect.
• The Joule-Thomson effect is an important part of
  our lives today, even though we may not be aware
  of it. Ordinary house hold refrigerators and air
  conditioners operate on this principle. First a
  gas is pressurized and cooled to an intermediate
  temperature by contact with a colder gas or
  liquid. Then the gas is expanded, and its
  temperature drops still further. The heat needed
  to keep this cycle operating comes from the
  inside of the refrigerator or the interior of a
  room, producing the desired cooling effect.
• METHODS OF LIQUIFICATION OF AIR
• Lindes system also known as hampson system.
• Claudes system.

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LINDES SYSTEM
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LINDES SYSTEM

• Clean dry air is taken from the atmosphere and is
  compressed up to 200 bar.
• The high pressure enters into counter flow air to
  air heat exchanger and is then throttled to atm -
  pressure.
• The J-T cooling up to expansion causes a lowering
  of temperature and this cool air is passed
  through heat exchanger where it cools the
  incoming high section.
• Thus the temperature at the valve is
  progressively lowered until the liquefaction
  temperature is reached.

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T-S DIAGRAM (Lindes system)
PROCESS 1-2 Compression 2-3 Pre-cooling of
air by pre cooling circuit 3-4 Pre-cooling of
air by Heat exchanger 4-5 Throttling
process 5-6 Process in evaporator
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CLAUDES SYSTEM DIAGRAM
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CLAUDES SYSTEM

• Claudes system yields more efficient cycle than
  Lindes system
• The expansion through an expansion valve is an
  irreversible process.
• In Claudes system energy is removed from the gas
  stream by using an expansion engine or expander.
• The expansion process is isentropic and much
  lower temp is attained then isenthalpic expansion
• In Claudes system the gas is first compressed to
  pressure of the order 4 Mpa.

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T-S DIAGRAM (Claudes system)
How Claudes system is more efficient than
Lindes system The advantage of the
Claudes system is, it operates at low
compression ratio compared with lindes
process. Secondly the temperature of air
before coming to the expansion valve in Claude
system is lower than the Linde system.
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APPLICATION OF CRYOGENICS

• Aerospace-cryogenic engines
• Medical Field
• Manufacturing field
• Electronics Field
• Fuels research.

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CRYOGENIC ENGINES IN AEROSPACE

• The first operational Cryogenic Rocket Engine is
  the 1961 NASA design the RL-10 LOX LH2 rocket
  engine.
• The upgraded cryogenic second-stage Pratt
  Whitney RL10B-2 engine is based on the 30-year
  heritage of the reliable RL10 engine.
• At Mahendragiri in Tamil Nadu, is the Liquid
  Propulsion System Centre LPSC. Here work on
  developing Indias own cryo - engines has been
  quietly moving. The system involves materials
  working at 250 deg below zero and pumps at speeds
  of 40,000 rpm. There are also complex metering,
  monitoring, integrating technologies involved.
  The engines are required to fire for about 700
  seconds during the final stage of a launch
  providing 7 tones of thrust..
• The Engine works on Staged Combustion Cycle
  with an integrated turbo pump running at around
  42,000 rotations per minute (rpm). It is also
  equipped with two steering engines developing a
  thrust of 2 kN each to enable three-axis control
  of the launch vehicle during the mission. Another
  unique feature of this engine is the closed loop
  control of both thrust and mixture ratio, which
  ensures optimum propellant utilization for the
  mission.

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CRYOGENICS IN MEDICAL FIELD
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• CRYOSURGERY
• Cryosurgery (also called cryo therapy) is the use
  of extreme cold produced by liquid nitrogen (or
  argon gas) to destroy abnormal tissue.
• Cryosurgery is used to treat external tumors,
  such as those on the skin.
• For internal tumors, liquid nitrogen is
  circulated through a hollow instrument called a
  cryoprobe.
• Cryosurgery has been used for many years in the
  treatment of skin cancer
• BENEFITS OF CRYOSURGERY
• Cryosurgery is very effective and is less
  expensive than other treatment. It can be done in
  your health care providers office and an
  anesthesia is not necessary.
• The treatment can be safely repeated and may be
  used along with standard treatments such as
  surgery, chemotherapy, Harmon therapy and
  radiation.
• It can be used for patients who are not good
  candidates for conventional surgery because of
  their age or other medical condition.
• It is used to treat skin lesions such as freckles
  (for cosmetic reasons), hemorrhoids and some skin
  cancers

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CRYOGENICS IN MANUFACTURING FIELD

• Cryogenic treatment works on Reamers, Tool bits,
  Tool punches, Carbide Drills, Carbide Cutters,
  Milling Cutters, Files, Knives, Reciprocating
  Blades, Dies and cutting tools.
• Stress relives ferrous and non ferrous castings
  and forgings for enhanced dimensional stability
  and surface finish upon finish machining.

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CRYOGENICS IN ELECTRONICS FIELD
The super conducting electronic devices like
SQUID (Super conducting quantum interference
device) are used in sensitive digital
magnetometers and voltmeters. Zero friction
bearings use magnetic field instead of oil or
air, derived from the Meissner effect associated
with super conductivity. Super conducting
electric motors are constructed approaching zero
electric loses.
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CONCLUSION

• Refrigeration and cryogenic cooling
  technology share a common history and there are
  many similarities in the underlying
  thermodynamics. The significant differences lie
  in the temperature range of interest and the
  properties of the working fluids.
• Whilst it is most unlikely that cryogens
  can ever replace more familiar refrigeration
  technology for high temperature cooling, there
  may be niche applications where they can offer an
  interesting alternative.

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REFERENCES

• Cryogenic engines, http//en.wikipedia.org
• Cryogenic engines, www.astronautix.com
• Cook P. Richatdson R.N., Cryogenic safety
  manual, see www.ior.org.uk
• GIST (Previously BOC Transhield), see
  www.gistworld.com

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