the net head and output power at rated
were considerably higher than predicted by the method of Sharma.
Furthermore the flow rate in turbine operation was slightly less
than that expected.
It is widely accepted that PATs require a higher head and flow at
BEP point than in pump mode, with the head ratio generally the
larger of the two. Ventrone et al. [7] suggests that this is due to a
combination of a significant increase in head coefficient with
increasing flow and the simultaneous decrease in mechanical losses
relative to power output as well as a residual negative
tangential velocity at operating condition just greater than design.