Positive displacement pump efficiency equation


The Volumetric Efficiency of Rotary Positive Displacement Pumps

Slip does not increase as pump speed increases, although the displaced quantity does increase. As a result, the faster a RPD pump is operated, the greater the volumetric efficiency, as illustrated in Table 1.

Positive displacement pump efficiency equation
Positive displacement pump efficiency equation

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Selection of the pumping equipment is a crucial point that determines both process parameters and in-use performance of the unit under development. During selection of the type of pump three groups of criteria can be distinguished:

Positive displacement pump efficiency equation

Reciprocating pumps

The choice between a centrifugal and positive displacement pumps is not always apparent and cannot be made without a full understanding of the differences. The fundamental difference is that positive displacement pumps, with the exception of air operated diaphragm pumps, are basically constant volume machines where flowrates are independent of pressure. Flow is dependent only on shaft revolutions per minute.

Positive Displacement vs Centrifugal Pump

Often times it is hard to determine when to use a centrifugal pump or a positive displacement pump. Each has its own unique properties with respect to flow rate, pressure, viscosity, and efficiency. What is the difference between a positive displacement pump vs a centrifugal pump?

Pump School: When to use a positive displacement pump

The choice between a centrifugal and positive displacement pumps is not always apparent and cannot be made without a full understanding of the differences. The fundamental difference is that positive displacement pumps, with the exception of air operated diaphragm pumps, are basically constant volume machines where flowrates are independent of pressure. Flow is dependent only on shaft revolutions per minute.

Positive displacement pump efficiency equation

Viscosity corrections to pump curve

You can check the "Quick Search" to display only the operating point in small size chart and move quickly from one pump to another with your editor and run the experiment:

Hydraulic fixed-displacement pumps: Review

In my continuing series on a mechanic’s guide to a hydraulic system, we have already discussed the importance of the fluid’s viscosity, cleanliness, flow rate, cooling and reservoir level to ensure a positive head pressure (NPSHA) to the suction side of the pump. Now, it’s time to discuss the heart of the hydraulic system—the pump.

Positive displacement pump efficiency equation

Positive displacement vs centrifugal

There are two main families of pumps; positive displacement and centrifugal (rotodynamic), both of which have their uses and best areas of application. It is important however to be able to identify when each pump type should be selected, which ultimately comes down to their working principle and the application at hand.