Correct Answer - Option 2 : Net head is zero
Volume flow rate:
Volume flow rate is the capacity and is simply mass flow rate divided by density.
\(̇ Q=\frac{̇ m}{\rho}\)
The performance of a pump is characterized by its net head H
\(H=({\frac{P}{{ρ g}} + \frac{{{v^2}}}{{2g}} + z})_{out}-({\frac{P}{{ρ g}} + \frac{{{v^2}}}{{2g}} + z})_{in}\)
Pump Performance
The maximum volume flow rate through a pump occurs when its net head (H) is zero. This flow rate is called Pump's free delivery.
The free delivery condition is achieved when there is no flow restriction at the pump inlet or outlet, in other words there is no load on the pump.
At this operating point, Q̇ is large, but H is zero.
The pump's efficiency is also zero because the pump is doing no useful work.