SUPPLY-KW/FLOW

5 posts / 0 new
Last post

eQuesters & DOE2-2ers,

The DOE2-2 dictionary loves to use the phrase, "total fan power per unit
flow" in defining SUPPLY-KW/FLOW. Clear as mud.
I figured this: At design conditions, the supply fan runs at 9.90 BHP
and 61.89% efficiency and the per-unit flow is at unity ( x CFM / x CFM =
1). The motor nominal efficiency is 93%. (No, I don't have a motor
efficiency curve.) 0.746 kW = 1 HP. Therefore, the fan kW = 9.90 *
0.746 / ( 0.6189 * 0.93 ) = 12.83 kW. The per unit flow is 1. So...
SUPPLY-KW/FLOW = 12.83, which I type into my .inp file.
Naturally, eQuest gives me an error message, insisting that
SUPPLY-KW/FLOW must be between 0.0 and .0080. Evidently, there is some
discrepancy involving units or the meaning of "per unit" in the context of
the quoted phrase.
Can anyone clarify what eQuest really means and how to calculate
SUPPLY-KW/FLOW? Is it supposed to be KW-per-CFM?
Thanks!

Lars Fetzek, EI

Lars Fetzek's picture
Offline
Joined: 2011-09-30
Reputation: 0

Question answered. Thanks, everyone.

Lars Fetzek, EI

Lars Fetzek's picture
Offline
Joined: 2011-09-30
Reputation: 0

Maybe I'm mistaken here, but I've always understood the Supply flow to
be kW/cfm. So if your design condition is 9.9 BHP, what is the design
flow rate (in cfm) that goes with that?

So for instance if your design flow rate is 20,000 cfm at 9.90 BHP, then
your Supply KW/Flow = 12.83/20,000 = 0.000642

Vikram Sami, LEED AP

Vikram Sami's picture
Offline
Joined: 2011-09-30
Reputation: 0

How about this:

9.9 BHP (output)/0.93 eff = 10.645 hp (input)
10.645 hp input x 0.7457 kW/hp = 7.94 kW

Brett Fero, P.E., LEED AP

Brett Fero's picture
Offline
Joined: 2011-09-30
Reputation: 0

Yes, but I think it refers to kW/cfm

Vikram Sami, LEED AP

Vikram Sami's picture
Offline
Joined: 2011-09-30
Reputation: 0