GPS-X Technical Reference

101 Suspended Growth Models
In the case of user-defined standard air (see Entering Airflow section below), the airflow
is calculated using Equation 6.15.
Equation 6.15
where:
molfr O2
MW O2
= mole fraction of O 2 in user-defined air (mole/mole)
= molecular weight of O 2 (32 g/mole)
P user = density of user-defined air (g/m 3 )
MW user
= average molecular weight of user-defined air (g/mole)
The airflow at either U.S. or European standard conditions is converted to field
conditions using the ideal gas law:
Equation 6.16
where:
T standard
T field
= air temperature at standard conditions (°C)
= air temperature at field conditions (°C)
Equation 6.16 assumes that the field air has the same humidity as the standard air. If the
humidity of the field air is different than for the standard air, the user can multiply the
GPS-X calculated field air by the ratio of the mole fraction of oxygen in the field air by
the mole fraction of air in the standard air.
No conversion to field conditions is undertaken for user-defined standard air.
GPS-X Technical Reference