Now look what I’ve done!  I’ve incited a techno-riot!

 

Don’t make me get the fire hoses & tear gas

 

I’m still laughing at the responses (which I suddenly realize, classifies me as a MAJOR GEEK ( but I already knew that :))

 

 

And Ed, anyone who can come-up with flow formulas w/ greek symbols and embed them into an email at will – is OK in my book

 

This forum is great!

 

 

Here is a formula for a centrifugal pump that clearly? Shows that Tracy and Lynn are correct

 

Energy Usage

The energy usage in a pumping installation is determined by the flow required, the height lifted and the length and characteristics of the pipeline. The power required to drive a pump (P_i), is defined simply using SI units by: by:

where:

P_i is the input power required (W)

ρ is the fluid density (kg/m³)

g is the gravitational constant (9.81 m/s²)

H is the energy Head added to the flow (m)

Q is the flow rate (m³/s)

η is the efficiency of the pump plant as a decimal

 

One can see that if Q the flow rate becomes zero (by blocking the exit) then the power required to drive the pump Pi also becomes zero.  So block the pump and lower the flow and the power required drops – or with the same power, the pump can spin faster.  There is always some flow around the vanes of a centrifugal pump in reality, so the power does not cause the pump to spin to infinity rpm but it equalizes at a higher rpm than when considerable (unblocked) flow is the condition.

 

Is this fun or what?

 

NO!  I meant exactly what I wrote.  It is admittedly counter-intuitive but true none the less.  Did you attempt to prove it to yourself with the suggested test?   Only takes a few seconds :>)

Tracy

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