EnergyPlus does its calculations using air
mass flow rate. The volume flow rates are reported by converting from mass
flow using an air density for dry air at standard conditions. The mass flow
values are more accurate; the volume flow values are more in line with how fan capacity
is characterized.
From:
EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of greenbuild15
Sent: Wednesday, August 05, 2009
1:22 PM
To:
EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support]
Definition of air flow rates
Hi Everyone,
I am not certain about the definition of air flow rates in EnergyPlus. (have
consulted both the Engineering & Input/Output references)
During simulations, I request output for:
Zone Mechanical Ventilation Volume Flow Rate [m3/s]
AirLoopHVAC Outdoor Air Mass Flow Rate AHU [kg/s]
AirLoopHVAC Mixed Air Mass Flow Rate AHU [kg/s]
According to the manual, Zone Mechanical Ventilation Volume Flow Rate [m3/s],
reports average OUTDOOR air volume flow rates to a zone.
The total for all zones (Converted to kg/s) differs from the AirLoopHVAC
Outdoor Air Mass Flow Rate AHU [kg/s].
Is this because the zone flows include ventilation flow not handled by the AHU
?
Regards,
Francois
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