page_title: Centrifugal pump selection and characteristics
section_title: Parameters and Definitions
hierarchical_section_title: Centrifugal pump selection and characteristics / Parameters and Definitions
caption_attribution_description: English: A visual schematic representation of pressure heads in a pump, showing the pump, piping system and the reservoirs.
context_page_description: The basic function of a pump is to do work on a liquid. It can be used to transport and compress a liquid. In industries heavy-duty pumps are used to move water, chemicals, slurry, food, oil and so on. Depending on their action, pumps are classified into two types — Centrifugal Pumps and Positive Displacement Pumps. While centrifugal pumps impart momentum to the fluid by motion of blades, positive displacement pumps transfer fluid by variation in the size of the pump’s chamber. Centrifugal pumps can be of rotor or propeller types, whereas positive displacement pumps may be gear-based, piston-based, diaphragm-based, etc.
  As a general rule, centrifugal pumps are used with low viscosity fluids and positive displacement pumps are used with high viscosity fluids.
context_section_description: Volume flow rate (Q), specifies the volume of fluid flowing through the pump per unit time. Thus, it gives the rate at which fluid travels through the pump. Given the density of the operating fluid, mass flow rate (ṁ) can also be used to obtain the volume flow rate. The relationship between the mass flow rate and volume flow rate (also known as the capacity) is given by:
  Where ρ is the operating fluid density.
  One of the most important considerations, as a consequence, is to match the rated capacity of the pump with the required flow rate in the system that we are designing.
  Discharge Head, is the net head obtained at the outlet of a pump. For a centrifugal pump, the discharge pressure depends on the suction or inlet pressure as well, along with the fluid’s density. Thus, for the same flow rate of the fluid, we may have different values of discharge pressure depending on the inlet pressure. Thus, discharge head (the height which the fluid can reach after getting pumped) varies according to its operating conditions.
  Total Head is the difference between the height to which the fluid can rise at the outlet and the height to which it can rise at the inlet for a centrifugal pump. This is a crucial parameter for pump selection and is a popularly used parameter for ascertaining industrial requirements. By eliminating the inlet head, we remove the effect of the supplied pressure to the pump and are left with only the pump’s energy (head) contribution to the fluid flow.
caption: Schematic representation of pressure heads in a pump.
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