Cryogenics
Cryogenics , Cryogenics (from Greek κρύος [kryos] "cold") or low-temperature technology is technology for producing lower temperatures ( Joule-Thomson effect ), and physical effects, for use at low temperatures (liquefaction and separation of gases). Cryogenic technology covers the temperature range below about −150 ° C. Temperatures of 77.4 K (−195.8 ° C), the boiling point of nitrogen , 20.4 K (with hydrogen ), and 4.2 K (with helium ) are technically easily accessible . Lower temperatures can be achieved by reducing the pressure and the associated change in the boiling point. With helium you can get down to approx. 1 K, with the (expensive) isotope 3 He even down to 1 mK. Liquid helium is widely used in the cooling of the superconducting windings of electromagnets.
Applications of cryogenics
- Energy technology ( nuclear fusion reactors )
- High energy physics ( particle accelerator )
- Vacuum technology ( cryopump )
- Energy technology (SMES energy storage, liquid hydrogen fuel)
- Rocket technology (e.g. pumps for liquid oxygen )
- Measurement technology ( cryo-electron microscopy , SQUIDs , detectors, NMR )
- Cryobiology ( Engl. Cryobiology )
- Process engineering (liquefaction of gases, low-temperature rectification, recycling)
- Cold grinding
- Production of technical gases
- Petrochemical , natural gas industry (natural gas liquefaction)
- Food industry (shock freezing)
- Energy recovery technology
- Electrical engineering, electronics
- Medicine : MRI , cryosurgery , extraction of medical gases
- Funeral services, promession
- Preservation , cryopreservation
- Cryonics or cryostasis
- Cryocontainers
Dangers with cryogenic gases
- Risk of suffocation and frostbite (freezer burn)
- Pressure increase due to evaporation
- Risk of fire from oxygen enrichment
- Thermal expansion
- Material embrittlement
Storage and transportation
Liquid nitrogen or liquid helium can be conveniently stored and transported in Dewar flasks for cooling purposes . Quick- release couplings are used for safe filling and transferring .
