Question

Why pumps are generally less efficient than turbines.

Answer 1

The  pump is inherently less efficient than a turbine because of smaller losses when converting pressure energy to kinetic energy than vice versa.

Answer 2

The difference in the efficiencies of pump and turbine is related to the fact that how fluids are handled by both machines.

A turbine keeps on expanding the working fluid from inlet. When this happens, the static pressure and the velocity of the fluid increases. This increase in velocity, further increases the kinetic energy of the fluid and this results in reduction of losses. Looses are minimized by keeping the layer of the fluid, thin at the boundary of the chamber.

In a pump, the entering fluid is accelerated and must be decelerated continuously, so as to increase the static pressure of the pump.

This task of pump is more challenging and difficult than that of a turbine. During deceleration ,the boundary layer increases in thickness and can also stop the system. Therefore, there are looses in case of pumps. Hence, pumps are less efficient than turbines due to huge losses in pumps.