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

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

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@xxxxxxxx





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