Variable speed pumps 1

[kkanel]

Has anyone ever studied the magnitude of the parasitic (due to hydraulic losses) consumption at part load of hydraulic couplings used to vary the speed of HP pumps at part load , compared to that when a frequency converter is used instead?
I am trying to establish without going into much detail whether the extra cost and complexity of a variable frequency driven motor is at 1st look justified by possible efficiency gains due to reduced(?) electrical consumption.

 

[ccfowler]

kkanel,

You would do well to do your own analysis for your specific circumstances. The combination of the system's ACTUAL head vs. flow characteristics, the pumps ACTUAL performance curves, the particular motor's performance characteristics, the adjustable speed drive's performance characteristics, the system's required flow variation duty cycle characteristics, the associated capital and operating costs, control system, maintenance and training needs, and assuredly, several other items of concern interact to determine which arrangement makes the most sense for the specific application. Any attempt to rely on some sort of rule of thumb or general comparision is likely to result in a poor choice. Your careful analysis may or may not show that a fixed speed pump is the best choice.