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[EnergyPlus_Support] Re: Pump Power calculations
I think I'm all set in that department. Thank you very much for your
patient assistance. I've got two more related items, if you haven't
run out of patience....
1) To make the pump power calculation more flexible, I suggest adding
a "pump efficiency" field, similar to the fan object. It's not a big
issue, but would be helpful.
2) The pump object shown below yields negative values for Watts at
very low flows. I have deliberately allowed zero as the minimum flow,
even though it's not realistic, so as to maximize the autosizing
function's convenience. It's not very much energy over the course of
a year, but a) is that supposed to be allowed in the E+ calculation
and b) if so, how about an automatic low limit of zero? This is also
minor, but since I am focussed on pumps at the moment, I decided to
pass it on.
Thanks again.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad
<RRaustad@...> wrote:
>
> The "d" in constants represents double precision. I should have taken
> that out before sending the email, but I was in a hurry. The 0.78 is
the
> assumed efficiency of the pump impeller. I found it in the Eng. Ref.
> under pump sizing. So TotalEff = Eff IMPELLER * Eff MOTOR. = 0.78 * 1.0
> = 0.78
>
> JV Dirkes II wrote:
> >
> > Dear Richard,
> >
> > Thank you for the additional info.
> > Clarification: Is the "0.78d0" below really just 0.78, or is it
> > something else? If it's 0.78, is that the assumed mechanical
> > efficiency of the pump?
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > <RRaustad@> wrote:
> > >
> > > Because I left out 1 important equation:
> > >
> > > TotalEffic = 0.78d0 * PumpEquip(PumpNum)%MotorEffic
> > >
> > >
> > > JV Dirkes II wrote:
> > > >
> > > > Dear E+ Forum,
> > > >
> > > > I've got the pump power equation figured out and am now trying to
> > > > reconcile the data in .eio with my calcs.
> > > >
> > > > Per .eio:
> > > > Rated Volumetric Flow Rate [m3/s] .0130493
> > > > Rated Power Consumption [W] 5041.09232
> > > >
> > > > My calcs say it should be:
> > > > .0130493 * 301322 = 3,932W (Note that efficiency = 1)
> > > >
> > > > Why is there a difference?
> > > >
> > > > PUMP:VARIABLE SPEED,
> > > > HtgWtr Pump_1, !- Pump Name
> > > > NodeIn_HtgWtr Pump_1, !- Inlet_Node
> > > > NodeIn_Boiler1, !- Outlet_Node
> > > > Autosize, !- Rated Volumetric Flow Rate {m3/s}
> > > > 301322, !- Rated Pump Head {Pa}
> > > > Autosize, !- Rated Power Consumption {W}
> > > > 1, !- Motor Efficiency
> > > > 0, !- Fraction of Motor Inefficiencies to
> > > > Fluid Stream
> > > > -0.006429, !- Coefficient1 of the Part Load
> > > > Performance Curve
> > > > 1.362214, !- Coefficient2 of the Part Load
> > > > Performance Curve
> > > > -0.348214, !- Coefficient3 of the Part Load
> > > > Performance Curve
> > > > 0, !- Coefficient4 of the Part Load
> > > > Performance Curve
> > > > 0, !- Min Flow Rate while operating in
> > > > variable flow capacity {m3/s}
> > > > CONTINUOUS, !- Pump Control Type
> > > > SchCpct_AlwaysOn; !- Pump Flow Rate Schedule Name
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "JV Dirkes II"
> > <jvd2pe@>
> > > > wrote:
> > > > >
> > > > > Dear Richard,
> > > > >
> > > > > So, pardoning my ignorance of SI, if
> > > > > %Power = %Head x %NomFlowRate / Eff
> > > > > does that mean that m3/s x Pa = W ?? (i.e., no units conversion
> > > > > constant? That doesn't seem right...)
> > > > >
> > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > > > > <RRaustad@> wrote:
> > > > > >
> > > > > > Straight out of the sizing routine...
> > > > > >
> > > > > > PumpEquip(PumpNum)%NomPowerUse =
> > > > > (PumpEquip(PumpNum)%NomPumpHead
> > > > > > * PumpEquip(PumpNum)%NomVolFlowRate) / TotalEffic
> > > > > >
> > > > > >
> > > > > > JV Dirkes II wrote:
> > > > > > >
> > > > > > > Dear E+ Forum,
> > > > > > >
> > > > > > > For ASHRAE 90.1 baseline models, a pump is limited to a
specific
> > > > unit
> > > > > > > power (e.g., 22W / gpm for chilled water pumps). I want to
> > autosize
> > > > > > > the pumps, but use a Delta P and motor efficiency that will
> > always
> > > > > > > result in the desired unit power. My derivation of that
Delta P
> > > > value
> > > > > > > does NOT result in the power level that I expect when I run
> > E+. So,
> > > > > > > either my derivation is incorrect, or E+ calculates the
> > power in a
> > > > > > > different manner.
> > > > > > > Will someone direct me to the E+ power formula for
situations
> > > > when the
> > > > > > > pump is autosized? I must be missing something, but
cannot find
> > > > it in
> > > > > > > "Help". Thanks!
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > --
> > > > > > Richard A. Raustad
> > > > > > Senior Research Engineer
> > > > > > Florida Solar Energy Center
> > > > > > University of Central Florida
> > > > > > 1679 Clearlake Road
> > > > > > Cocoa, FL 32922-5703
> > > > > > Phone: (321) 638-1454
> > > > > > Fax: (321) 638-1439 or 1010
> > > > > > Visit our web site at: http://www.fsec.ucf.edu
> > <http://www.fsec.ucf.edu>
> > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>
> > > > > >
> > > > > > UCF - From Promise to Prominence: Celebrating 40 Years
> > > > > >
> > > > >
> > > >
> > > >
> > >
> > > --
> > > Richard A. Raustad
> > > Senior Research Engineer
> > > Florida Solar Energy Center
> > > University of Central Florida
> > > 1679 Clearlake Road
> > > Cocoa, FL 32922-5703
> > > Phone: (321) 638-1454
> > > Fax: (321) 638-1439 or 1010
> > > Visit our web site at: http://www.fsec.ucf.edu
<http://www.fsec.ucf.edu>
> > >
> > > UCF - From Promise to Prominence: Celebrating 40 Years
> > >
> >
> >
>
> --
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL 32922-5703
> Phone: (321) 638-1454
> Fax: (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
>
> UCF - From Promise to Prominence: Celebrating 40 Years
>
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