Re: [EnergyPlus_Support] Re: ATUs - Insufflated vs. Exhaust Air flows

["Michael J. Witte" <mjwitte@xxxxxxxx>]

Cross mixing simply exchanges and equal amount of air between two zones.  It is 
a zone heat balance function and the air handling system knows nothing of it.

On 11 Jan 2008 at 17:52, anarui.oliveira wrote:

> Thanks a lot for all your answers.
> 
> Regarding option 4:
> - If I use Cross-mixing instead, doesn't the program account for the 
> corresponding outgoing flow in the source zone?
> 
> Thanks again,
> Ana Rui.
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> <mjwitte@...> wrote:
> >
> > 1. First, I will clarify some terminology:
> > Return air flow - air leaving the zone and returning to the HVAC 
> system
> > 
> > Exhaust air flow - air leaving the zone and exhausted to outdoors
> > 
> > Return air flow rate is computed as Supply air flow minus Exhast 
> air flow
> > 
> > I am not sure when you say "exhaust" if you mean return or exahust 
> as defined 
> > above.  I will use my definitions below.
> > 
> > 2. The systems created by Compact HVAC assume that return air flow 
> is equal to 
> > supply air flow.  
> > 
> > 3. If you want to add exhaust air flow, you can add ZONE EXHAUST 
> FAN objects by 
> > editing the expidf file.  
> > 
> > 4. If you want to model a constant (or scheduled) flow from one 
> zone to 
> > another, you can use a MIXING object to move air from one zone to 
> another.  
> > However, the HVAC system has no knowledge of this and the user must 
> balance the 
> > airflows by adding a dummy ZONE EXHAUST FAN to the source zone to 
> cause a 
> > reduction in return air flow from the source zone.
> > 
> > 5. For constant volume systems, you can use 
> AIRFLOWNETWORK:DISTRIBUTION:* 
> > objects to model the pressure-indcued flows, but this feature does 
> not yet 
> > support VAV systems.
> > 
> > Mike
> > 
> > 
> > On 9 Jan 2008 at 16:23, anarui.oliveira wrote:
> > 
> > > Hi.
> > > 
> > > The parameters for ATU, such as those cretated by
> > > - Compact HVAC:Zone:VAV,
> > > - Compact HVAC:System:VAV,
> > > only allow the user to define the insufflated air flows (Supply 
> air 
> > > flow), right?
> > > 
> > > What does the simulation assume, in this case, for the exhaust 
> air 
> > > flows, and how does it deal with the corresponding effect on the 
> > > inside pressures?
> > > 
> > > If the case to model has different insufflated and exhaust flows, 
> how 
> > > does it affect my model? Wow can I implement this in E+?
> > > 
> > > And if a certain zone only has forced exhaust flow, and the inlet 
> > > flow is assumed to be drawn from adjacent areas by pressure 
> > > difference?
> > > 
> > > Thanks in advanced.
> > > 
> > > Best regards,
> > > Ana Rui.
> > > 
> > > 
> > > 
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov
> > > 
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> > > 
> > > Attachments are not allowed -- please post any files to the 
> appropriate folder
> > > in the Files area of the Support Web Site.
> > > 
> > > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf 
> under the
> > > Documentation link and press the "search" button.
> > > 
> > > Yahoo! Groups Links
> > > 
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support      
> > EnergyPlus-Support@...
> >
> 
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
> Documentation link and press the "search" button.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 






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