Prepared: Сенімтайқызы Гүлім Аширмухамбетов Бақытжан
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- Prepared:Сенімтайқызы Гүлім Аширмухамбетов Бақытжан Көшербай Ержігіт Әділбек Оңалбек Пахратдинов Алмат Шалман Әділет
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СРС 9. Fundamentals of low temperature physics. The main stages of the development of low -temperature physics. The production of liquid oxygen in the form of fog. Preparation of liquid oxygen and nitrogen as a liquid. Preparation of liquid hydrogen. The invention of Dewar vessel for the long -term storage of cryogenic liquids Prepared:Сенімтайқызы Гүлім Аширмухамбетов Бақытжан Көшербай Ержігіт Әділбек Оңалбек Пахратдинов Алмат Шалман Әділет Оспанжан Диас Has accepted: Соколов Д.Ю Low temperature physics - branches of physics that study the physical properties of systems at low temperatures. In particular, this section considers such phenomena as superconductivity and supermanufacturability. Physics, which measures observable physical processes occurring at very low temperatures, down to the absolute content of materials, includes the study of properties at low and ultralow temperatures, and thus is taken into account with many areas of science and technology Methods for obtaining low temperaturesEvaporation of liquidsLiquefied gases are usually used to obtain and maintain low temperatures. In a Dewar vessel containing liquefied gas evaporating under atmospheric pressure, a constant temperature of normal boiling of the refrigerant is maintained well enough. The most commonly used refrigerants are liquid nitrogen and liquid helium. Previously used liquefied hydrogen and oxygen are now used quite rarely due to the increased explosive hazard of vapors. Nitrogen and helium are practically inert and the danger is only a sharp expansion during the transition from a liquid to a gaseous state.By reducing the pressure above the free surface of the liquid, it is possible to obtain a temperature below the normal boiling point of this liquid. For example, pumping nitrogen vapors can achieve a temperature up to a triple point temperature of 63 K, pumping hydrogen vapor (above the solid phase) can achieve a temperature of 10 K, pumping helium vapor can achieve (under very good experimental conditions) a temperature of about 0.7 K. ThrottlingMain articles: Throttling and the Joule — Thomson EffectWhen flowing through the narrowing of the passage channel of the pipeline — choke, or through a porous partition, the pressure of gas or steam decreases along with a decrease in its temperature. The throttling effect is mainly used for deep cooling and liquefaction of gases. Expansion with the completion of external workMain article: ExpanderIt is possible to cool the gas using an expander — a device for additional cooling of the gas by releasing it under pressure into a cylinder with a piston that moves with force. At the same time, the gas performs work and cools down. It is used in the liquid helium production cycle.If you use a turbine instead of a piston, you will get a turbo expander, the principle of operation of which is similar. Adiabatic demagnetizationMain article: Adiabatic demagnetizationThe method is based on the effect of heat release from paramagnetic salts during their magnetization and subsequent absorption of heat during their demagnetization. This makes it possible to obtain temperatures up to 0.001 K. To obtain very low temperatures, salts with a low concentration of paramagnetic ions are most suitable, that is, salts in which neighboring paramagnetic ions are separated from each other by non-magnetic atoms. Peltier EffectMain article: Peltier EffectThe Peltier effect is used in thermoelectric cooling devices. It is based on lowering the junction temperature of semiconductors when a direct electric current passes through them. The amount of heat released and its sign depend on the type of contacting substances, the current strength and the time of passage of the current, that is, the amount of heat released is proportional to the amount of charge passed through the contact. жүктеу/скачать 278.58 Kb. Достарыңызбен бөлісу:
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