Basics of Pump Pressure/Velocity
Basics of Pump Pressure/Velocity
(OP)
The numbers I'm giving below are totally made up and are being asked for fundemental understanding only:
Say I want a pump that can pump a fluid 5 ft/s with a pressure of 5 psi;
1. I understand that the 5 ft/s is a direct result of how fast the blades of the impeller are pushing the water along on a macroscopic scale. Is this correct?
2. Is the 5 psi actually the pressure that gets "put into" the fluid or is it more the pumps potential capability to overcome a back pressure? Can you provide me with an analogy of how this happens? For example, is this dependent on the speed or torque of the motor?
Sorry if this question seems "out of left field"
Regards,
Tom
Say I want a pump that can pump a fluid 5 ft/s with a pressure of 5 psi;
1. I understand that the 5 ft/s is a direct result of how fast the blades of the impeller are pushing the water along on a macroscopic scale. Is this correct?
2. Is the 5 psi actually the pressure that gets "put into" the fluid or is it more the pumps potential capability to overcome a back pressure? Can you provide me with an analogy of how this happens? For example, is this dependent on the speed or torque of the motor?
Sorry if this question seems "out of left field"
Regards,
Tom





RE: Basics of Pump Pressure/Velocity
RE: Basics of Pump Pressure/Velocity
Pumps add energy to the fluid flowing through it, how much is dependent on the efficiency of the pump.
You should take some time and study the extended Bernoulli equation to better understand pressure and velocity relationships.
http://en.wikipedia.org/wiki/Bernoulli's_principle
RE: Basics of Pump Pressure/Velocity
A trip to the library or a search on the net for pump terminology wouldn't hurt you.
RE: Basics of Pump Pressure/Velocity
http://www.mcnallyinstitute.com/index.html
RE: Basics of Pump Pressure/Velocity
A pump creates head (ft, m, whatever), not PSI. The pump ALWAYS runs on the pump curve. Basically the pump is just reacting to the TDH of the system. If you have 30ft vertical pipe on the discharge, and the pump dead-heads at 30ft, then you have 0 flow, and 30ft of head (/2.31 = psi). If you have 0ft of pipe on the discharge, then the pump is producing no head, and at 'run-out' flow (i.e. 25gpm)
As far as impeller diameter, pump speed, pipe diameters... You need to look up the Affinity Laws.
RE: Basics of Pump Pressure/Velocity
2.) A pump adds energy to the fluid. That energy can be converted to either potential energy , static head, head with no flow, "dead head", or kinetic energy, velocity head at full flow, "runnout", or any point inbetween those two extremes, such as, by judicious use of a discharge control valve.
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"Pumping systems account for nearly 20% of the world's energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies) http://virtualpipeline.spaces.live.com/