Case well water pump efficiency in variable speed applications
Case well water pump efficiency in variable speed applications
(OP)
We are looking to build a variable speed, constant pressure water well system for use in a geothermal grid. We would like to use a 1.0-1.5HP system to flow between 10-21GPM. This pump would also provide drinking water.
I have contact OEMs regarding pump efficiency other than 60hz synchronous operation but not much info. I would really like to know if a pump that is optimized for max eff at 33GPM, what would the eff look like at half speed? These would be multi stage cased well 4" pumps. I would like to take advantage of the service factor in a 1HP pump and overspeed the pump slightly so we can get the best possible performance at the mostly required 10-15GPM.
I have contact OEMs regarding pump efficiency other than 60hz synchronous operation but not much info. I would really like to know if a pump that is optimized for max eff at 33GPM, what would the eff look like at half speed? These would be multi stage cased well 4" pumps. I would like to take advantage of the service factor in a 1HP pump and overspeed the pump slightly so we can get the best possible performance at the mostly required 10-15GPM.





RE: Case well water pump efficiency in variable speed applications
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Case well water pump efficiency in variable speed applications
RE: Case well water pump efficiency in variable speed applications
RE: Case well water pump efficiency in variable speed applications
RE: Case well water pump efficiency in variable speed applications
Divide hydraulic power by pump power for efficiency.
Then add all the inefficencies of the VFD, including its embedded energy.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Case well water pump efficiency in variable speed applications
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Case well water pump efficiency in variable speed applications
You want to vary power from 1 to 1.5 HP, 50%, but flow by 100%
The "linear relation of water flow and power requirement" is more like cubed.
"OEMs did not have any charting for performance at alt speeds", should tell you something. Nobody runs them at alt speeds. They are already inefficient enough.
You might have a handle on something, but its not pump flow. Pumps this small don't use enough energy to save anything worthwhile, nor are they efficient enough to warrant use of a VFD in such a low efficiency system. You're going to try to save 20% of the energy use by adding a VFD consuming 5-10%
You've already spent all the money you might have saved with a VFD, if you would have saved any at all and that's highly unlikely, on design time for this problem. Don't lose any more.
We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer