RE: [EnergyPlus_Support] Re: Definition of air flow rates

Those report variables do not include outdoor air from simple ZoneVentilation. They do include outdoor air from both ZoneHVAC:* equipment and AirLoopHVAC-based AHUs.

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of greenbuild15
Sent: Wednesday, August 05, 2009 3:25 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Definition of air flow rates

Thanks Brent,

I appreciate your fast answer!

Just one point that I need to get clarity on :
Do zone flows indeed include ventilation flow not handled by the AHU ?

Much appreciated,

Francois

--- In EnergyPlus_Support@yahoogroups.com, "Griffith, Brent" <brent.griffith@...> wrote:
>
> 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@yahoogroups.com [mailto:EnergyPlus_Support@yahoogroups.com] On Behalf Of greenbuild15
> Sent: Wednesday, August 05, 2009 1:22 PM
> To: EnergyPlus_Support@yahoogroups.com
> 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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