User Manual
7
Be sure to use the same absolute units for
pressure
(i.e. PSIA, mm Hg absolute,
...)
and temperature
(ºK or ºR). The result is the standard volumetric flow rate at
the
given standard conditions.
Standard volumetric flow rate
=
Actual volumetric flow rate x
x
This equation can be rewritten: (B x DP + C x DP²) x
x
x
Table A-31031 lists the values of Pf/
Pstd
absolute line pressures from 26”Hg at 0.05” Hg intervals.
The standard pressure is 29.92” Hg absolute for this table. Table A-32422 lists the values of
(Tstd / Tf) x (µstd / µf) for air from 50 to 159ºF in 1º intervals. The standard temperature is 70ºF
(529.67ºR) for this table.
Note:
If you are flowing wet air, a humidity correction factor for standard volumetric flow rate must
be
used.
The difference between wet-air density
(Pwet)
and dry-air density (Pdry) increases with
temperature and humidity. At 80°F and 80% relative humidity, the ratio of
Pwet
/ Pdry is .990. Table
A-35600 lists the ratio
Pwet
/ Pdry of air from 40 to 100°F and from 20 to 100%
relative
humidity.
The equation for standard volumetric flow rate of flowing wet air becomes:
Standard Volumetric Flow
Rate
Wet Air
=
(B x DP + C x DP²) x
x
x
x
Mass Flow Rate
Multiply the standard volumetric flow rate by the density of the flowing gas at standard conditions to
obtain the mass flow rate of that gas.
Mass Flow rate = Standard volumetric flow rate x density @ standard conditions
Summary
Curve/table value @ DP =
(B x DP + C x DP²)
Actual volumetric flow rate = (B x DP + C x DP²) x
Standard volumetric flow rate = Actual volumetric flow rate x
x
Mass flow rate = Standard volumetric flow rate x density @ standard conditions