A centrifugal pump containing two or more impellers is called a multistage centrifugal pump. The impellers may be mounted on the same shaft or on different shafts. For higher pressures at the outlet impellers can be connected in series. For higher flow output impellers can be connected in parallel.
A common application of the multistage centrifugal pump is the boiler feed water pump. For example, a 350 MW unit would require two feed pumps in parallel. Each feed pump is a multistage centrifugal pump producing 150 l/s at 21 MPa.
All energy transferred to the fluid is derived from the mechanical energy driving the impeller. This can be measured at isentropic compression, resulting in a slight temperature increase (in addition to the pressure increase).