
171Fluid Flow
1 atm11325 bar 76 cm mercury
468 in WC
==
=
1 bar 9869 atm1 kPa
14 5 38 psi 29 53 in mercury
==
==
9.4.2 Atmospheric Pressure
Atmospheric pressure refers to the pressure created by a
column of air that extends from the surface of the earth
to several miles above. Initially, engineers developed a
Standard Atmospheric Pressure so that the performance of
aircraft and missiles could be evaluated at a standard
condition. The idea of a standard atmospheric pressure
was rst introduced in the 1920s.
24
In 1976, a revised
report was published, which dened the U.S. standard
atmosphere that is the currently accepted standard. Thi ...