Pump Efficiency
The measure (usually given as a percentage) of how effectively a pump transfers energy from a rotating energy source (Prime Mover such as an engine or electric motor), into the fluid.
With input energy stated as 100%, a pump with 65% efficiency transfers 65% of the available energy from the rotating input source into fluid energy, the remaining 35% being lost to inefficiencies.
Overall Efficiency
For an electric motor driven pump:
Overall Efficiency = pump efficiency x motor efficiency
Best Efficiency Point (BEP)
The highest efficiency point for a centrifugal pump is called the Best Efficiency Point or BEP. BEP is the performance point where a centrifugal pump transfers input energy from a prime mover such as an electric motor or engine, into fluid power with minimum losses to inefficiency.
There is only one BEP for a centrifugal pump. To learn why follow the link below to see a Pump Curve showing the BEP and drawings illustrating the concepts behind efficiency and why a pump is most efficient at one point.
Related Subjects on this Website:
Glossary - Best Efficiency Point (BEP)
Glossary - Pump Characteristic
Glossary - Power Characteristic
Most often described as the ability to do work. There are two types of energy:
Potential (PE) - Energy stored, or the ability to do work based on the position or configuration of a mass. The specific type of potential energy may be described with terms such as: "Gravitational Potential Energy", "Electrical Potential Energy", "Magnetic Potential Energy", "Elastic Potential Energy", and others.
Potential Energy is expressed in numerous ways:
1 - Gravitational Potential Energy
U = - [G x M x m] ÷ r
Where:
G = Universal Gravitation Constant
M = Mass 1
m = Mass 2
r = Distance between the 2 masses
2 - Large Body Gravitational Potential Energy
An adaptation of 1 for Calculations on large, concentric, stable, rigid bodies such as Earth's Surface: U = mgh
Where:
m = Mass of Earth
g = Gravity
h = Reference point Height, (Earth's Surface)
3 - Electrical Potential Energy
E = Q x V
Where:
Q = Charge
V = Voltage
Kinetic (KE) - Energy of motion, the energy contained in mass due to its motion. This motion and therefore the energy measurement is relative, depending on the viewpoint of the measurement.
Kinetic Energy is expressed as E = 1/2mV2
Where:
E = Energy
m = mass
V = velocity
Gas bubbles carried within a fluid flow. Gas bubbles may be in the fluid flow due to pump intake leaks, or the gas is purposely injected, or the gas bubbles can arise from gasses coming out of solution. Gas is sometimes injected into a fluid flow to dissolve the gas into the fluid for chemical treatment purposes. Gas may also be injected to increase intake pressure and eliminate cavitation.
Entrained gas bubbles are very different from cavitation bubbles which are really more properly called "cavities". Entrained gas does not sound like cavitation and has little in common with cavitation. Entrained gas bubbles will not harm pumps as long as the pump seal does not become dry, and as long as the gas bubbles do not reach sufficient volume to excessively impede flow or cause an air lock in the intake line or within the pump itself.
Gas bubbles will not damage the materials used to construct the pump like cavitation will, because cavity collapse involves extremely high pressures and temperatures. Gas bubbles or entrained gasses enter into solution within the liquid by means of diffusion, a slow process incapable of producing high temperatures or pressures.
Related Subjects on this Website:
Glossary - Dissolved Substances & Gasses
Glossary - Suction Specific Speed
Liquids can carry solid or semi-solid substances such as sand within the fluid flow. If the particles are heavier than the fluid then flow velocity and turbulence must be high enough to successfully carry the particles along with the pumpage.
Fluids carrying relatively large amounts of entrained solids are called Slurries.
Most centrifugal pumps will handle very small amounts of entrained solids with no problem but are not guaranteed to do so. Irrigation Craft does not offer any guarantee to handle entrained solids.
Fluids relatively free of entrained solids are said to be clear fluids.
Discussions of pumps on this website assume there are very few entrained solids (such as sand) in the pumpage.
Related Subjects on this Website:
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