What type of pump operates by adding energy to water in a set volume?

The correct answer is positive displacement pump. This type of pump operates by trapping a fixed amount of water and then forcing that volume into the discharge pipe, effectively adding energy to the water as it moves through the system. The mechanism behind positive displacement pumps involves expanding and contracting chambers or using mechanical devices to push water forward with each cycle.

Positive displacement pumps are particularly effective in applications where precise flow control is necessary, as they deliver a constant flow rate regardless of changes in pressure within the system. This makes them suitable for a variety of irrigation tasks where maintaining an even water supply is essential.

Other types of pumps, like centrifugal pumps, operate on a different principle. They use a rotating impeller to increase the velocity of the water, which then converts that velocity into pressure for flow; thus they do not rely on the displacement of a fixed volume. Submersible pumps are a specific type of centrifugal pump designed to operate underwater, and while reciprocating pumps can also be positive displacement, they are characterized by a back-and-forth motion rather than a simplifying mechanism of a single volume of fluid.