Brinell viscosity

The unit is lippascal? second

The sign of viscosity is μ, and the unit is Pascal second (Pa·s).

Defined by the following formula: L = μ μ 0/h

μ0—— the speed at which the flat plate moves parallel to the fixed flat wall in its own plane.

H—— Distance from flat plate to fixed flat wall. But this distance should be small enough to make the fluid flow between the flat plate and the fixed flat wall laminar.

L—— Fluid friction acting on unit area when the plate moves.

The symbol of kinematic viscosity is V, and kinematic viscosity is the ratio of dynamic viscosity of a substance to its density in engineering calculation, and the unit is: (m2/s). The unit is secondary meters per second (m2/s).

v=μ/p

Viscosity has dynamic viscosity, and the unit is Pascal second (Pa s); "engler viscosity" is also used in petroleum industry, not the viscosity concept introduced above. It is a reading directly measured by the fluid in Engra viscometer.

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The measurement methods of viscosity can be divided into absolute viscosity and relative viscosity. Absolute viscosity can be divided into dynamic viscosity and kinematic viscosity. Relative viscosity can be expressed in several ways, such as engler viscosity, Cedell viscosity and Reynolds viscosity.

1, dynamic viscosity η Let two areas in the fluid be 1m2, the distance be 1m, and the resistance generated when the relative moving speed be 1m/s be called dynamic viscosity. The unit is pa.sec. In the past, the unit of dynamic viscosity was poise or centipoise, which was an illegal unit of measurement.

1pa.s =1n.s/m2 =10pa =10 cubic CP = 1kcps.

The TM D445 standard stipulates that the kinematic viscosity is used to calculate the dynamic viscosity, that is, η = η-the dynamic viscosity in the formula η, the density in the Pa.s period, and η-the kinematic viscosity unit is kg/m3. M2/s in Chinese national standard GB/T506-82 is a method for measuring the dynamic viscosity of lubricating oil at low temperature. This method is used to determine the dynamic viscosity of lubricating oil and dark petroleum products at low temperature (0 ~-60℃). Under the conditions of strictly controlling temperature and different pressures, the time required for a certain volume of sample to flow through a calibrated capillary viscometer is measured in seconds. The dynamic viscosity is calculated by the product of the sample flowing through the capillary, the capillary calibration constant and the average pressure, and the unit is Pa s. The difference between the two results determined repeatedly by this method should not exceed 5% of its arithmetic mean.

2, kinematic viscosity υ The ratio of the dynamic viscosity η of a fluid to the density ρ of a fluid at the same temperature is called kinematic viscosity. It is a measure of the flow resistance of this fluid under the action of gravity. In the International System of Units (SI), the unit of kinematic viscosity is m2/s. In the past, cSt was usually used as the unit of kinematic viscosity, which was equal to 10-6m2/s (i.e. 1cSt= 1mm2/s).

Kinematic viscosity is usually measured by capillary viscometer. Under strict temperature and reproducible driving head, the time for a certain volume of liquid to flow through the calibrated capillary viscometer under the action of gravity is measured. In order to accurately measure the kinematic viscosity, the temperature of the measured fluid must be controlled at first, and the temperature measurement accuracy should reach 0.065438 0℃. Secondly, the appropriate capillary size must be selected to ensure that the outflow time can not be too long or too short, that is, a slightly thicker capillary is used for viscous liquid and a slightly thinner capillary is used for thinner liquid, and the flow time can not be less than 200 seconds; Viscosity tube constant must be calibrated periodically; In addition, the viscosity tube must be installed vertically. The national standard of kinematic viscosity is GB/T256-88, which is equivalent to ASTM D445-96/IP7 1/75.

3. Engler viscosity 0E China's national standard is the determination of Engler viscosity of petroleum products GB/T266-88. This is a commonly used relative viscosity in the past, which is defined as the ratio of the time (s) required for 200ml liquid to flow through Engel viscometer at a specified temperature to the time (s) required for the same volume of distilled water to flow through Engel viscometer at 20℃.

4. redwood Viscosity This viscosity is mainly used in Britain and Japan. It is defined as the time required for 50 ml of test oil to flow through the Reynolds viscometer at the specified temperature of 60℃ or 98.9℃, and the unit is seconds.

5. Cyberport Universal Viscosity This is a common viscosity unit in the United States. It is defined as the time, in seconds, required for 60ml of liquid to flow out of the Cyberport viscometer at a specific temperature. The American standard method is ASTM D88.

6. Conversion of several viscosities 1) Conversion of Engler viscosity and kinematic viscosity

Kinematic viscosity nu (mm2/s) = 7.310e-6.310e2) Conversion between Reynolds viscosity and kinematic viscosity nu (mm2/s) = 0.26r-172/r when r >; At 225s, the conversion between zeta (mm2/s) = 0.26R3) Cyberport viscosity and kinematic viscosity is: at s >, zeta (mm2/s) = 0.225 s; 285s uses the above formula.