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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