Page 189 - Centrifugal Pumps 2E

168 Centrifugal Pumps: Design and Application

Figure 10-35. CO 2 pipeline pump (courtesy BW/IP internal, Inc. Pump Division,
1
manufacturer of Byron Jackson/United " Pumps).

Horsepower Considerations

As liquid CO 2 is compressible, special consideration during the pump
selection process must be given to horsepower requirements. Gas horse-
power (GHP) and brake horsepower (BHP) should be calculated, and it is
recommended that pump shaft and driver be sized to accommodate the
larger of the two. Depending on the thermodynamic properties, GHP can
be greater or less than BHP. To calculate GHP, it is necessary to predict
the behavior of the liquid across the pump. This can be done either from
interpolation of thermodynamic tables (assuming pure CO 2) or by com-
puter calculations using the new equation of state for the actual composi-
tion (see Starling 1973). This method has been widely applied to predict
the behavior of any mixture of hydrocarbons. While it is recommended
that final pump design be based on computer calculations, preliminary