How does a positive displacement pump move fluid?

How does a positive displacement pump move fluid?

• A. It relies on changing pressure by velocity head to move fluid.
• B. It displaces a fixed volume of fluid with each pump cycle.
• C. It requires a vacuum to draw fluid via suction.
• D. It uses a turbine to drive fluid.

Answer: (B)

A positive displacement pump moves fluid by trapping a specific amount of fluid and then forcing that exact volume out with each pump cycle. Because the volume per cycle is fixed, the pump delivers a predictable, fixed amount of fluid for each stroke, and the overall flow rate scales with how fast the cycles occur. This behavior is what makes positive displacement pumps effective for precise dosing and handling viscous liquids—the volume moved per cycle doesn’t depend on the fluid’s velocity head. The other descriptions don’t capture the essential principle. Using pressure from velocity head describes how some dynamic pumps (like centrifugal types) generate flow, but they don’t move a fixed volume per cycle. Relying on a vacuum to draw fluid is not the defining mechanism of a positive displacement pump, even though some designs create suction. A turbine might drive the pump, but that’s about the energy source, not how the pump moves fluid per cycle.

A positive displacement pump moves fluid by trapping a specific amount of fluid and then forcing that exact volume out with each pump cycle. Because the volume per cycle is fixed, the pump delivers a predictable, fixed amount of fluid for each stroke, and the overall flow rate scales with how fast the cycles occur. This behavior is what makes positive displacement pumps effective for precise dosing and handling viscous liquids—the volume moved per cycle doesn’t depend on the fluid’s velocity head.

The other descriptions don’t capture the essential principle. Using pressure from velocity head describes how some dynamic pumps (like centrifugal types) generate flow, but they don’t move a fixed volume per cycle. Relying on a vacuum to draw fluid is not the defining mechanism of a positive displacement pump, even though some designs create suction. A turbine might drive the pump, but that’s about the energy source, not how the pump moves fluid per cycle.