To transfer pressure, a piston positive displacement pump uses which principle?

A piston positive displacement pump operates based on the principle of incompressibility of liquids. This principle asserts that liquids cannot be compressed, meaning their volume remains constant under pressure. When the piston moves within the cylinder of the pump, it creates a space that allows liquid to enter, and as it moves back, it forces the liquid out into the discharge line. This movement effectively transfers pressure, as the pumping action relies on the incompressibility to generate a consistent flow of liquid regardless of variations in pressure at the pump's outlet.

Understanding the incompressibility of liquid is vital, as it ensures that the pump can maintain and transfer pressure effectively without encountering significant loss of flow or volume. The other principles listed do not accurately describe the operation of a piston positive displacement pump; for instance, a pressure gradient relates to differences in pressure that drive flow, but it doesn’t define how the pump itself functions. Similarly, vacuum suction and thermal expansion do not apply to the mechanics of how a piston pump generates and transfers pressure within its system.