[EnergyPlus_Support] Re: Zone components of a 2-pipe system?

["anarui.oliveira" <anarui.oliveira@xxxxxxxxx>]

Thanks a lot.

The Central AHU has a heat recovery component, which receives the 
return airflow from more than 1 zone, so I think I should keep the 
two levels of the heating/cooling process?...as opposed to letting 
the fan-coils addressing the full thermal load?...
In this case, it appears it wouldn't actually be easier to treat the 
heat recovery by "manual" post-processing?...Or are there any known 
downsides to this two-level approach?

At the moment, is there any approach in E+ that would accurately 
mimic the system I described? I mean, could I actually (with nore or 
less "manual work"), set up both a heating and a cooling coil to act 
on the supply air, at zone level, setting both coils operation to 
depend on the zone thermostat (at the moment, I don't really need 
many details on this, I would just like to know the possibilities)?

Again, thanks a lot,
Ana Rui.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
<mjwitte@...> wrote:
>
> If I am understanding the system correctly, the simplest approach 
would be to 
> use the 4-pipe fan coil with mutually exclusive schedules for the 
heating and 
> cooling coils.  However, do not set the inlet conditions to be from 
the central 
> ahu, simply let the fancoil unit carry the entire load.  
> 
> It is not clear to me whether it matters that the heaitng/cooling 
be modeled in 
> two parts.  If it does matter, then I would still use the 4-pipe 
fan coil, but 
> with no outside air.  And then describe a constant volume air loop 
which 
> delivers the partially conditioned outside air using a direct air 
terminal unit 
> in each zone.  If the direct air unit is listed with heating and 
cooling 
> priority 1,  then the fan coil will pick up any remaining load.
> 
> Mike
> 
> 
> On 26 Jan 2008 at 17:03, anarui.oliveira wrote:
> 
> > Hello, all.
> > 
> > I'm having a hard time to figure out the best options to model a 
> > specific 2-pipe HVAC configuration...
> > 
> > Any ideas about which could be the simplest way to approximate 
the 
> > zone level model of a 2-pipe (constant volume) system with:
> > - an AHU that delivers 100% OA at inermediate heated/cooled 
> > temperatures (18/27 ºC) to the zone level,
> > - where a battery with either hot or chilled water coil (mutually 
> > exclusive at any given moment, and necessarily in the same 
operation 
> > regime - heating or cooling - serving the central AHU) meets the 
> > additional load (when needed),
> > - raising/decreasing the air temperature of the supply air loop 
to 
> > design Temperatures of 35ºC(heating) or 16ºC (cooling), to meet 
Room 
> > Air setpoint conditions according to a 20-25ºC thermostat?
> > 
> > The "Single Duct:Const Volume: Reheat" and "Single Duct:Const 
Volume:4 
> > pipe" don't quite seem to reproduce this behaviour?...
> > 
> > No recirculating or induced air from the room actually happens in 
the 
> > real situation (the zone level re-conditioning is performed 
directly 
> > and uniquely in the air supplied by the AHU, and then delivered 
to the 
> > room, where the mixed model should take care of the rest)...
> > ...but perhaps, in terms of global thermal loads and energetic 
> > analysis, it wouldn't be too far fetched to use
> > - "Single Duct:Const Volume:4 pipe"
> > or
> > - "direct air" and "fan coil: 4 pipe"
> > with mutually exclusive availability schedules for the coils and 
> > design air inlet temperatures equal to the setpoints of AHU 
supply 
> > air?...
> > ... the main differences between these options being?...
> > 
> > Better options?...
> > 
> > Thanks in advance,
> > 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@...
>




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