Dear Vinay,
While .6 fan efficiency is within normal range, the goal is to
define a combination of fan efficiency and pressure rise which results in the
acceptable fan power. You start with known air flow, make a reasonable estimate
of fan efficiency and then derive the pressure rise.
For a “Proposed” system, the derivation is not
needed; you use the actual fan and motor efficiencies, actual airflow and
actual pressure rise.
For your information (just in case it’s helpful), the
derivation of fan power is shown below in IP units.
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Vinay
Devanathan
Sent: Wednesday, July 07, 2010 9:32 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] ASHRAE Compliant Fans and Pumps
Mr. Dirkes,
Thanks for your reply. So, is 0.6
Fan Efficiency (including motor efficiency) acceptable? or does it depend on
any other variable? I am assuming there are no set specifics for Fan Efficiency
value. So, with this procedure, we can calculate Fan Power from Appendix G
formula and adjust Pressure difference. Am I right on this?
Thank you.
Regards,
Vinay
On Wed, Jul 7, 2010 at 9:25 PM,
James V Dirkes II, PE <jvd2pe@xxxxxxx>
wrote:
Dear
Vinay,
ASHRAE
90.1-2007 specifies Baseline system fan power in Table G3.1.2.9. For VAV
systems, also use Table G3.1.3.15 for part load performance. A sample
object for the VAV fan is shown below.
For
all baseline fans, I made a spreadsheet which, based on anticipated motor and
fan efficiency, calculates the pressure rise which will result in the correct
ASHRAE 90.1 fan power. Remember that E+, when asking for “fan
efficiency”, really wants (Fan mechanical efficiency x Motor efficiency).
For example, if the fan mechanical efficiency = .60 and motor efficiency
= .90, the E+ “fan efficiency” = .54.
|
|
Fan:VariableVolume |
|
Name |
SFan_MainBldg |
|
Availability Schedule Name |
SchCpct_FanOpern |
|
Fan
Efficiency (incl. motor) |
0.6 |
|
Pressure Rise (Pa) |
498 |
|
Maximum
Flow Rate |
Autosize |
|
Minimum
Flow Rate |
0 |
|
Motor
Efficiency |
MT |
|
Motor
In Airstream Fraction |
1 |
|
Fan
Coefficient 1 |
0.0013 |
|
Fan
Coefficient 2 |
0.147 |
|
Fan
Coefficient 3 |
0.9506 |
|
Fan
Coefficient 4 |
-0.0988 |
|
Fan
Coefficient 5 |
0 |
|
Air
Inlet Node Name |
NodeOut_ClgCoilAir_MainBldg |
|
Air
Outlet Node Name |
NodeOut_SFan_MainBldg |
|
End-Use
Subcategory |
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of Vinay Devanathan
Sent: Wednesday, July 07, 2010 5:53 PM
Subject:
Re: [EnergyPlus_Support] ASHRAE Compliant Fans and Pumps
Alan,
In regards to your reply,
Does ASHRAE specify any efficiency value for the fans? If yes, could you please
direct me to the same.
Thank you.
Regards,
Vinay
On Tue, Jun 29, 2010 at 11:33 AM, Jackson,
Alan <ajackson@xxxxxxxxxxxxxxxxx>
wrote:
You're going to want to adjust
your Static Pressure DeltaP. Once you
have your Watts for the Baseline from auto sizing the flow you can use
DeltaP[Pa] = Power[W]*Eff/Flow[m3/s]
Since ASHRAE is telling you Flow and Power you have to solve for static.
Alan Jackson, LEED AP
KlingStubbins
-----Original Message-----
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of eddiecorwin
Sent: Tuesday, June 29, 2010 11:13 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] ASHRAE Compliant Fans and Pumps
I am curious as to how people have gone about modeling ASHRAE compliant
pumps and fans.
The pumps seem relatively strait forward, run the model, see what the
flow is, then enter in a wattage that equates to 22W/GPM. The fans,
however, do not have an input for the rated wattage. The only option I
see is to alter the fan's Motor Efficiency until you get close to the
correct W/CFM.
Are these the same methods people have applied in the past, or is there
a better way to the the correct W/GPM and W/CFM?
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