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[EnergyPlus_Support] Re: Fan Electric Power
Thank you, for everything.
Ana.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "JV Dirkes II"
<jvd2pe@...> wrote:
>
> Dear Ana,
>
> Communicating only in text makes things more difficult! I'll try
again
> (still using US units of measure)!
>
> Using this example:
>
FAN:SIMPLE:VARIABLEVOLUME,
> Fan Name RFan_AH1,
> Available Schedule SchCpct_FanOpern,
> Fan Total Efficiency 0.485,
> Delta Pressure 995, (4" w.c.)
> Max Flow Rate 13.1372, (27,836 CFM)
> Min Flow Rate 0,
> Motor Efficiency .91,
> Motor In Airstream Fraction 1,
> FanCoefficient 1 .0013,
> FanCoefficient 2 .147,
> FanCoefficient 3 .9506,
> FanCoefficient 4 -.0998,
> FanCoefficient 5 0,
> Fan_Inlet_Node NodeOut_EA_AH1,
> Fan_Outlet_Node NodeOut_EFan_AH1;
> End-Use Subcategory
>
> Notes:
>
> * Max Flow Rate is selected from equipment data (as shown
above) or
> determined from the .eio file when autosizing. As mentioned
previously,
> remember to include the effect of any sizing parameter. Also, for
a VAV
> fan, make sure that it's actually operating at peak flow or the
> coefficients will be active and reduce power consumption.
>
> * Delta pressure is selected from equipment data
> * Fan Total Efficiency is taken from equipment data (Note that
the IO
> Reference defines this as INCLUDING the motor efficiency)
> For this fan, I expect power to be:
>
> Brake HP = CFM * DeltaP / TotalEff'y / 6,356
>
> W = CFM * DeltaP / TotalEff'y / 6,356 * 746
>
> = 27,836 * 4 / .485 / 6,356 * 746
>
> = 26,945
>
> When I run this fan object in an E+ model, the .csv file reports
26,761W
> at the time when Flow Rate = Max Flow Rate. That's pretty close
> agreement!
>
> I hope this helps.
>
> p.s., I applaud your error checking efforts. With hundreds or
thousands
> of inputs, it is very important to make sure the output makes sense!
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "anarui.oliveira"
> <anarui.oliveira@> wrote:
> >
> > Sorry, could you add some legends to make sure I'm looking at the
> > right variables?...
> > If I understood, those calculations correspond to an independent
> > estimate of electric power consumption of the fans?
> >
> > In the cases when I detected large differences between E+ and
> > supplier data, the supplier data indicated straightforward
electric
> > power consumption of the fans... and delta-Pressure and nominal
> > airflow. I used that dP and airflow (which does not vary
> > significantly beacuse I was using CAV models) to feed to E+ and
> > obtain its electric power estimate... I had also high values of
> > (total) efficiency (above 0.7), but even trying to reduce those
in E+
> > did not increase the power estimate to values anywhere near the
> > supplier data...
> >
> > I guess the supplier data may sometimes include the effect of the
> > selected fans not working at nominal conditions for the intended
> > aiflows, but still... differences of twice over?...
> >
> > Anyway, thanks for everything,
> > Ana.
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "JV Dirkes II"
> > jvd2pe@ wrote:
> > >
> > > Dear Ana,
> > >
> > > I get excellent agreement for fan power when using (US
> > measurements):
> > >
> > > BHP = CFM x Î"P
> > > η x 6,355
> > >
> > > = f3 x in. w.c. x 62.316 lb x min-HP
> > > min η ft2 x 12 in. w.c.
> 33,000
> > > ft-lb
> > >
> > > = CFM x Î"P
> > > η x 6,355
> > >
> > > It is important to know the mechanical efficiency of the
fan "η"
> > > from a fan chart, or to derive it from known Brake HP.
> > >
> > > Also, you must make sure that the E+ report reflects the correct
> > flow. A
> > > relief fan, for example, may never operate at the rated airflow
and
> > the
> > > .eio report only shows Watts for the modeled airflow. The .ssz
will
> > > show the design airflow.
> > > If you are using a sizing factor greater than 1.0, don't forget
to
> > use
> > > the rated airflow x sizing factor as your basis for power
> > calculations.
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "anarui.oliveira"
> > > <anarui.oliveira@> wrote:
> > > >
> > > > Hi, me again.
> > > >
> > > > Has anyone tried to compare the E+ estimates of Fan Electric
Power
> > > with
> > > > rated electric consumptions for these equipments?
> > > > I've been trying to "calibrate" these values, but I keep
getting
> > E+
> > > > plus estimates much lower than supplier data (like 2 to 10
times
> > > > smaller values, for E+ estimate of Fan electric power).
> > > >
> > > > Regards,
> > > > Ana Rui.
> > > >
> > >
> >
>
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