1.4.3. Pressure
Fig. 1.15:
Atmospheric pressure
Atmospheric pressure p
amb
[bar]
Atmospheric pressure is caused by the weight of the air that surrounds us. It is independent of the density and height of the atmosphere.
At sea level, 1 013 mbar = 1,01325 bar
= 760 mm/Hg [Torr]
= 101 325 Pa
Under constant conditions atmospheric pressure decreases the higher the measuring location is.
p
amb
= atmospheric pressure
p
abs
= Absolute pressure
p
op
= Over-pressure
p
vac
= Partial pressure
Fig. 1.16:
Illustration of different pressures
Over-pressure p
op
[bar
op
]
Over-pressure is the pressure above atmospheric pressure. In compressed air technology, pressure is usually specified as over-pressure, and in bar without the index"op".
Absolute pressure p
abs
[bar]
The absolute pressure
p
abs
is the sum of the atmospheric pressure
p
amb
and the over-pressure
p
op
.
p
abs
= p
amb
+ p
op
According to the
SI-System
pressure is given in Pascal [Pa]. In practice, however, it is still mostly given in "bar". The old measure atm (1 atü = 0,981 bar
op
) is no longer used.
1 bar = 10195 mmWH [ mm water head ]
[last chapter]
. .
1.4. Physical fundamentals
. . . .
1.4.1. Temperature
. . . .
1.4.2. Volume
. . . .
1.4.3. Pressure
* You are here *
. . . .
1.4.4. Volume flow
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