Information AboutCoolant |
| CATEGORIES ABOUT COOLANT | |
| cooling technology | |
| coolants | |
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The coolant can either keep its phase and stay liquid or gaseous, or can undergo a Phase Change , with the Latent Heat adding to the cooling efficiency. The latter, when used to achieve low temperatures, is more commonly known as Refrigerant . GASES Air is a common form of a coolant. Air Cooling uses either Convective airflow (passive cooling), or a forced circulation using Fan s. Inert Gas es are frequently used as coolants in gas-cooled Nuclear Reactor s. Helium is the most favored coolant due to its low tendency to absorb neutrons and become radioactive. Nitrogen and Carbon Dioxide are frequently used as well. Sulfur Hexafluoride is used for cooling and insulating of some high-voltage power systems ( Circuit Breaker s, Switch es, some Transformer s, etc.). Steam can be used where high Specific Heat Capacity is required in gaseous form and the corrosive properties of hot water are accounted for. LIQUIDS The most common coolant is Water . Its high Heat Capacity and low cost makes it a suitable heat-transfer medium. It is usually used with additives, like Corrosion Inhibitor s and antifreezes. Antifreeze , a solution of a suitable organic chemical (most often Ethylene Glycol , Diethylene Glycol , or Propylene Glycol ) in water, is used when the water-based coolant has to withstand temperatures below 0 °C, or when its boiling point has to be raised. Very pure Deionized Water , due to its relatively low Electrical Conductivity , is used to cool some electrical equipment, often high-power transmitters. Heavy Water is used in some nuclear reactors; it also serves as a Neutron Moderator . Oil s are used for applications where water is unsuitable.
Cutting Fluid is a coolant that also serves as a Lubricant for metal-shaping Machine Tool s. Liquid Fusible Alloy s can be used as coolants in applications where high temperature stability is required, eg. some Fast Breeder Nuclear Reactor s. Sodium or sodium- Potassium alloy NaK are frequently used. Another liquid metal used as a coolant is Lead , in eg. Lead Cooled Fast Reactor s. Some early Fast Neutron Reactor s used Mercury . For very high temperature applications, eg. Molten Salt Reactor s or Very High Temperature Reactor s, molten Salt s can be used as coolants. One of the possible combinations is the mix of Sodium Fluoride and Sodium Tetrafluoroborate (NaF-NaBF4). Freon s were frequently used for immersive cooling of eg. electronics. Refrigerant s are coolants used for reaching low temperatures by undergoing phase change between liquid and gas. Halomethane s were frequently used, most often R-12 and R-22 , but due to environmental concerns are being phased out, often with Liquified Propane or other haloalkanes like R-134a . Anhydrous Ammonia is frequently used in large commercial systems, and Sulfur Dioxide was used in early mechanical refrigerators. Heat Pipe s are a special application of refrigerants. Liquid gases are used as coolants for Cryogenic applications, namely applications using Superconductor s, or extremely sensitive Sensor s and very low- Noise Amplifier s. The most common and least expensive coolant in use is Liquid Nitrogen . Liquid Air is used to lower degree, due to its oxygen content which makes it prone to exploding in contact with combustible materials. Lower temperatures can be reached using liquefied Neon . The lowest temperatures, used for the most powerful Superconducting Magnet s, are reached using Liquid Helium . Fuel s are frequently used as coolants for engines. A cold fuel flows over some parts of the engine, absorbing its waste heat and being preheated before combustion. Kerosene and other Jet Fuel s frequently serve in this role in aviation engines, Liquid Hydrogen is used to cool nozzles and chambers of Rocket Engine s. SEE ALSO
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