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Vacuum freeze drying machine concept and measuring unit

2020/10/02
Concept of vacuum vacuum freezing dryer


absolute vacuum is no gas space state, but actually there is no such vacuum environment.



we usually said vacuum vacuum freezing dryer refers to a certain space, the atmospheric pressure is lower than gas state, also said that the number of molecules of gas inside the space density is lower than the atmospheric pressure in the region of number density of gas molecules.

different vacuum state, is the space with different number density of molecules, such as in the standard state ( STP: 0 degrees, 101325 pa) The number of molecules of the gas density of 2. 6870 * 10/25m / - 3, and in a vacuum, density of 1 * 10 / - 4 pa, the number of molecules of the gas density is only 2. 65 * 10/16m / - 3

( 2) Vacuum freeze drying machine vacuum unit of measure

in vacuum is commonly used in vacuum freezing dryer technology to measure vacuum degree of thin gas space. Usually vacuum degree by the pressure value of the gas, the lower the pressure value, the higher vacuum degree; The lower the pressure value, the higher the vacuum degree.

common pressure units have

( 1) PASCAL: pressure unit in international units, legal pressure units in China. Pa pressure is 1 square meter area 1 n the action of force that is

1 pa = 1 n/m2


barye: 1 barye pressure is 1 cm2 area function 1 dyn force or


1 barye = 1 dyn/cm2


standard atmosphere: in 1927, the seventh international conference on measurement, to defined, under normal atmospheric pressure in gravity acceleration for 980. Temperature of 0 degrees 665 cm/s2, mercury, mercury density to 13. Under the condition of 5915 g/cm3, high 760 mm hg pressure called 1 ATM is


1 ATM = 760 MMHG = 1013250 dyn/cm2

the measuring accuracy of this standard atmosphere depends on the density of mercury, is strict enough.

in 1954, the tenth international conference on measurement and redefines the standard atmospheric pressure, namely,

1 ATM = 1013250 dyn/cm2 = 101325 pa
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