Minimum flow rate of centrifugal pumps is determined by the following criteria:
-temperature rise due to internal energy loss.
-internal recirculation in the impeller (with large
impeller inlet diameter compared with outside diameter,
the NPSH rises in the part-load range).
-increased vibration due to greater flow separation.
-increased pressure fluctuation at part load.
-increased axial thrust at low flow rates.
-increased radial thrust (especially with single-volute
pumps).