Cryogenics1

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Cryogenics-An introduction

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Cryogenics1

  1. 1. CryogenicsThe coolest thing ever!
  2. 2. What is cryogenics?• The word cryogenics stems from Greek word cryos and means "the production of freezing cold“, the term is used today as a synonym for the low-temperature state.• Cryogenics is the study of the production of extremely cold temperatures. This field of science also looks at what happens to a wide variety of materials from metals to gases when they are exposed to these temperatures
  3. 3. 1) The development of cryogenics as a low temperature science is a direct result of attempts by nineteenth century scientists to liquefy the permanent gases.2) Michael Faraday, had succeeded, by 1845, in liquefying most of the gases then known to exist.3) His procedure consisted of cooling the gas by immersion in a bath of ether and dry ice and then pressurizing the gas until it liquefied.
  4. 4. • The use of cryogenics or freezing technique seems to have it’s roots way back.• Here’s how- Starting back about 150 years ago Swiss watchmakers gave birth to cryogenics. They would bury their watch parts in the snow for a winter because they noticed that it would make them more durable and therefore keep better time. Tool and die makers of the 1930’s that noticed that freezing tool steel would help it hold an edge better than tool steel that hadn’t been frozen
  5. 5. ApplicationsMagnetic resonance imagingElectric power transmission in big citiesFrozen foodForward looking infrared (FLIR)Blood bankingRocket enginesTo make metals durable
  6. 6. How do we use it?• Magnetic Resonance imaging(MRI)a. MRI is a method of imaging objects that uses a strong magnetic field to detect the relaxation of protons that have been perturbed by a radio-frequency pulse.• Electric power transmission in big cities• It is difficult to transmit power by overhead cables in big cities, so underground cables are used.• But underground cables get heated and the resistance of the wire increases leading to waste of power.• Superconductors are frequently used to increase power throughput, requiring cryogenic liquids such as nitrogen or helium to cool special alloy-containing cables to increase power transmission.
  7. 7. • Frozen fooda. When very large quantities of food must be transported to regions like war zones, earthquake hit regions, etc., they must be stored for a long time, so cryogenic food freezing is used.• Forward looking infrared (FLIR)a. Many infra-red cameras require their detectors to be cryogenically cooled.• Blood bankinga. Certain rare blood groups are stored at low temperatures, such as - 165 degrees C.
  8. 8. What cryogenics is and what it is not.• People generally confuse cryogenics with cryonics..• Cryonics is one of the applications of cryogenics or• cryogenics is the tree and cryonics the branch!• Let’s see the difference between their definitions• Cryogenics• The branches of physics and engineering that involve the study of very low temperatures.• Cryonics• The emerging medical technology of preserving humans and animals with the intention of future revival.
  9. 9. Relation between cryogenics and cryonics Cryonics Cryogenics
  10. 10. Cryogenics and NASA• Astronomers at the Goddard Space Flight Center are working to develop ever more sensitive sensors to catch even the weakest signals reaching from the stars. Many of these sensors must be cooled well below room temperature to have the necessary sensitivity. Here are some examples of how cooling helps:• Infrared Sensors: infrared rays, also called "heat rays" are given off by all warm objects. Infrared telescopes must be cold so that their own radiation doesnt swamp the weak infrared signals from faraway astronomical objects.• Electronics: all sensors require electronics. Cooling electronics reduces the noise in the circuits and thus allows them to study weaker signals.• X-rays: the sensors for XRS, the X-Ray Spectrometer measure temperature changes induced by incoming x-rays. When the sensors are colder, the induced temperature changes are larger and easier to measure.
  11. 11. Cryogenics in rocketengines
  12. 12. Cryogenics in rocket engines• A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer (or both) are gases liquefied and stored at very low temperatures.• Notably, these engines were one of the main factors of the ultimate success in reaching the Moon by the Saturn V rocket.• During World War II, the warring countries discovered that rocket engines need high mass flow rate of both oxidizer and fuel to generate a sufficient thrust. At that time oxygen and low molecular weight hydrocarbons were used as oxidizer and fuel pair.
  13. 13. • At room temperature and pressure, both are in gaseous state. Hypothetically, if propellants had been stored as pressurized gases, the size and mass of fuel tanks themselves would severely decrease rocket efficiency.• Therefore, to get the required mass flow rate, the only option was to cool the propellants down to cryogenic temperatures (below −150 C, −238 F), converting them to liquid form.• Hence, all cryogenic rocket engines are also, by definition, either liquid-propellant rocket engines or hybrid rocket engines.
  14. 14. Cryogenic processing in industries• The process is based on what is placed in the chamber.• It starts with placing the parts in a controlled cryogenic chamber and the ramp down starts with ultra-cold nitrogen gas. The materials are slowly cooled with nitrogen gas only and then slowly introduced to liquid nitrogen for the duration of the “soak” period. (20+ hours depending on what is being treated)• The liquid phase provides the most efficient and uniform deep cryogenic soak at a consistent temperature of –320 deg. F (impossible to do with gas alone).• With cryogenics two factors that make for a better end product are temperature (the colder the better) and time (the longer the better). Materials are then allowed to return very slowly to room temperature. At that time, those materials that specifically require post-cryo tempering are moved into a tempering oven to complete the tempering procedure.
  15. 15. • Some cryogenic companies use gas only treatment methods and only reach.• The use of precisely controlled temperature profiles avoids any possibility of thermal shock and thermal stress that is experienced when a part is subjected to abrupt or extreme temperature changes.• Though liquid nitrogen is used, no part is introduced to the liquid until it has been slowly cooled to cryogenic temperatures by the ultra-cold nitrogen gas. By eliminating the need for circulation fans and on- board heating elements are chambers remain 100% moisture free during the entire process.

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