I am trying to review a proposed modification to the pump power curve in an eQuest model of a variable flow chilled water system. Please explain how the pump power curve works (PUMP-POWER-fFLOW). The quadratic equation appears to give a dimensionless factor between 0.37 and 1.0 for a range of inputs between 0 and 1.0... Is this factor applied against an internal theoretical power calculation to account for the pump/motor efficiency changes at part load?
Thanks in advance for your help.
Shawn
Shawn Wilson, PE LEED AP
Hi Shawn,
Yes... and yes!
This curve, which can be read as "Pump Power as a function of Flow" uses the hourly flow (expressed as a fraction of 100% design flow) to return a "normalized" (dimensionless) factor that is multiplied against the design power consumption (kW) input for the pump to determine the hourly power consumption. For the numbers you've provided, the curve describes input power draw approaching 37% of full load as GPM approaches zero.
For a study focused on pump curve differences, note the design power consumption ("PUMP-KW") is itself an optional input, and if not provided will be figured by eQuest from the various head/flow/efficiency inputs. Could save you some time to be sure that's set as intended.
If you have the time, would be curious to learn what you're demonstrating specifically - maybe something we could all learn from =)?
Regards,
~Nick
[cid:489575314 at 22072009-0ABB]
NICK CATON, P.E.