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



I understand now about the source zone.

But what about the RECEIVING zone of a MIXING object? This inlet flow 
is accounted for to balance the supply and return air flows of an ATU?

In this case, could I have a zero supply air flow and a non-zero 
return air flow, based on the inlet flow of the MIXING object?

Always thankful for your help,
Ana Rui.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
<mjwitte@...> wrote:
>
> 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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