[EnergyPlus_Support] Re: How to control the outdoor air rate and total air flow rate in the HVAC system?

["jpei82" <jpei82@xxxxxxxxx>]

Thank you so much for your reply! Now I have some questions, :)

1. If constant volume system is used, the OA flow and the primary 
loop air flow rate will be constant as designed, right?

2.if I still use VAV system, but change the VAV terminal unit min 
flow fraction to 1, and set the primary loop flow rate, then the sum 
of zone flow rate will be the primary loop flow rate, am I correct?
3. if 2) is correct, the real OA flow will be the same as set in zone 
sizing. is that true? 

Since I am a beginner of EnergyPlus, Thank you so much again for 
patience!

Jingjing
  

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
<mjwitte@...> wrote:
>
> The values in zone sizing objects and the desing flow rates will 
occur when the 
> system is running a full flow.  For a VAV system, this will not 
occur very 
> often - only on the hottest days and during recovery from setback.
> 
> For VAV systems, the outside air flow rate can be proportional to 
the system 
> flow rate (which means the outside air fraction remains constant), 
or a fixed 
> amount (which means the outside air fraction varies).  See 
CONTROLLER:OUTSIDE 
> AIR for more details.  But note that the VAV terminal unit min flow 
fractions 
> must be consistent with the OA requirement.  If the total system 
supply air 
> flow falls below the min OA requirement, the OA flow will also 
drop, even when 
> using the fixed amount OA control.
> 
> Mike
> 
> 
> On 9 Jan 2008 at 23:20, jpei82 wrote:
> 
> > Hi, all, now I want to simulate the energy consumption difference 
> > between different ourdoor air flow rate. I specify the required 
OA flow 
> > rate in "zone sizing" by "outside air flow per zone", but found 
that 
> > the "zone mechanical ventilation volume flow rate" in the result 
does 
> > not agree with the value I specified. what is the reason? 
> > 
> > Also , I give a fixed value in "design air flow rate" 
for "primary air 
> > loop"  , but the volume flow rate for "mixed air node" (also VAV 
sys 
> > inlet node, VAV sys outlet node, they have the same value), is 
not the 
> > value I gave, but much smaller. I supposed they should be the 
same. Can 
> > anyone tell me the reason? Thanks a lot!
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> > 
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> > http://groups.yahoo.com/group/EnergyPlus_Support/
> > 
> > Attachments are not allowed -- please post any files to the 
appropriate folder
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> > 
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under the
> > Documentation link and press the "search" button.
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> > 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@...
>




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