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The concept of fluid pressure
Published on:2015-1-15 8:32:53 Hits:

We define vertical and uniform force acting on the unit area of the pressurized fluid.

The formula P = 1

Where P - fluid pressure acting;

F - force;

A - the role of the area.

In the International System of Units, the force F in Newton (N), the role of the unit area A is m 2 (m 2), the pressure P unit is N / m 2, or Pascal (Pa).

There are different concepts in real life pressures and production.

(1) atmospheric pressure: atmospheric pressure is the pressure on the surface of the earth by weight of the air column arising. Symbol PB said atmospheric pressure changes with different weather conditions, such as altitude and latitude.

(2) gauge pressure: pressure gauge indicated instrument called gauge pressure, which is based on atmospheric pressure to zero starting pressure. Represented by the symbol P G. Table pressure is usually practical engineering stress.

(3) absolute pressure: is not included in any full starting pressure conditions. That is, all the pressure of liquids, gases and vapors in which space. It is equal to the atmospheric pressure and gauge pressure sum. P A symbol says:

P A = P G ten P B

(4) sparse air pressure: When the absolute pressure is less than atmospheric pressure, differential pressure and absolute pressure of the atmosphere known as the sparse air pressure, also known as vacuum pressure, negative pressure. Symbol P H said::

P H = P B - P A

(5) differential pressure (pressure): The difference between two related stress, the common symbols Δ P representation.

Of absolute pressure, gauge pressure, atmospheric pressure, and differential pressure between the vacuum pressure available under the graph.

Chen said pressure concept, the flow measurement is also often use the static and dynamic pressure concept:

(6) Static: Static pressure refers to the fluid flow rate without the influence of the measured pressure value table. For example: For pipe flow by measuring the pressure wall spaces, both static pressure value. In the past by the hydrostatic pressure of the liquid column height indicated called the head, high water to the skin, said

Hydrostatic called hydrostatic head.

1.gif

Relationship absolute pressure, gauge pressure, atmospheric pressure and true space

1.gif

Velocity profile within the tube

(7) dynamic pressure: dynamic pressure refers to the kinetic energy possessed by a fluid per unit volume. Usually calculated using 1/2 ρν 2.

Where ρ-- fluid density;

v - velocity of the fluid.

Dynamic pressure, also known as dynamic pressure.

Pressure of the fluid measured by a variety of pressure measurement instrumentation. Common spring pressure gauge pressure measurement instrumentation, fluid pressure gauge and so on.

Pressure of the fluid flow measurement is a very important parameter. Differential pressure flowmeter is the use of measuring both ends of the cutting pieces

To achieve flow measurement of the pressure difference. Also known work by measuring the pressure of the pressure meter, make the necessary corrections meter

Considered to ensure the accuracy of flow measurement.


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