What is Positive Displacement?
Positive displacement is a term used in fluid dynamics to describe a type of pump or compressor that works by trapping a fixed amount of fluid or gas and then forcing it through the system at a constant rate. It refers to the fact that the pump or compressor displaces a fixed volume of fluid or gas with each cycle of operation.
It is also known to a type of mechanism used in pumps and compressors that moves a fixed volume of fluid or gas through a system. Positive displacement pumps and compressors work by trapping a volume of fluid or gas in a chamber and then moving that chamber through the system. In these systems, a specific amount of fluid or gas is moved for each cycle of the mechanism, regardless of changes in pressure or flow.
These systems are often used in applications where a precise flow rate is required, such as in chemical processing or food production. They are also useful in systems where high pressures are required, as positive displacement pumps and compressors can create much higher pressures than centrifugal systems.
Examples of these kind of devices include reciprocating pumps, screw pumps, gear pumps, and roots blowers. These devices are commonly used in a wide range of industries, including oil and gas, chemical processing, food and beverage, and wastewater treatment.
In contrast to dynamic pumps, which use centrifugal force to move fluid, positive displacement pumps and compressors rely on mechanical action to move fluid or gas through the system. Besides, positive displacement is different from other types of pumps and compressors, such as centrifugal pumps, which rely on the kinetic energy of a fluid to move it through the system. In centrifugal pumps, the fluid is accelerated and then decelerated, creating a pressure difference that drives the flow of fluid. This means that the flow rate in a centrifugal pump varies with changes in pressure, whereas in a positive displacement pump, the flow rate is constant.