Since87
where on earth did you get that RD-12 ? awfully nice piece of gear
(WAY beyond my budget !)
I think your model is a bit 'loose'
the pump shaft (or rotating magnet if mag drive) is connected to an impeller having curved vanes rotating in an enclosure
- at no flow there is no rotating 'disk' of water, but rather a violently churned mass in which the vanes can get no clean 'bite'; they have zero efficiency albiet max pressure - due to the cavitating vanes the motor is relatively unloaded
- as the flow increases, the effectiveness of the vanes does so as well, increasing the load on the motor and slowing it slightly
- maximum efficiency relates to the specific pump design and motor combination and is decsribed in Mgal / kWh (units probably wrong - all this was years ago)
- as the (back) pressure continues to decrease the flow will increase but as the vane configuration is no longer ideal the specific efficiency will start decreasing as well, though the total work performed will still be increasing
jeez, I'm sorry I started this; despite tweaking its not all that good a model either
I guess you don't have access to a pump handbook ?
even Marks describes this as I recall
well, leave it for Dave
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