pumping in parallel 1

[mechanicaldup]

what is the power consumption when pumping in paralel?

do you add the individual power consumptions of each pump?

 

[bulkhandling]

Yes.

 

[electricpete]

If you had one pump running and started a second in parallel, the power would not double... you have to find the new operating point as the intersection of the system curve with the two-pump curve (double the flow rate at any head). The knowing the operating point use the head (dp) to go back to the individual pump curves to determine the bhp for each.

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[mechanicaldup]

in effect, what system would consume the more power, the single pump system delivering the same flow & head OR the parallel system?

 

[bulkhandling]

That depends on how is the system designed. If you have one pump with a system curve joint at close to the Best Efficiency Point, and you add the second pump in parallel without modifying the piping system (except for the piping around the pump), the combined pump curve will join the system curve at left side of the BEP with lower efficiency. That means, the pumps consume more power than the increase in flow delivery.

If you added the second pump while modifying the piping system (with larger pipe size)to make the total friction lose same as previous for one pump, you are getting doubled flow with same efficiecy - just like as if you added a parallel system.

 

[Bjegovic]

one big pump will probably have better efficiency than two smaller pumps delivering same Q,H; but this effect is not important compared to other design issues (proces demands, reliability...and commercial offers!)

usually we consider that by increasing pump size, relative dimensions of gaps and tolerances decrease, resulting in better efficiency.