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Re: [EnergyPlus_Support] Re: Zone components of a 2-pipe system?
The key requirement that you are looking for here is zone-level cooling coils
for more than one zone on a central air loop. The only EnergyPlus objects
which provide this are the induction unit and the fan coil.
I can think of 2 approaches to modeling this:
1. Use a central air loop system with central heating and cooling coils and
SINGLE DUCT:CONST VOLUME:4 PIPE INDUC terminal units. Set the Induction ratio
to 1.0. You must have induced air flow because this is where the zone-level
heating and cooling coils are place. For heat, the energy use will be no
different than it would if the reheat coils were placed as you describe. For
the recool coil, the latent/sensible split may be affected because the
conditions entering the coil will be different (zone conditions instead of
preconditioned central air). But this should be fairly close.
2. Use a central air loop system with central heating and cooling coils and
DIRECT AIR terminal units plus FAN COIL UNIT:4 PIPE or UNIT VENTILATOR to model
the zone-level coils. From a modeling perspective, options 1 and 2 are very
similar, but option 1 requires less input.
Mike
On 30 Jan 2008 at 10:31, anarui.oliveira wrote:
> 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@...
> >
>
>
>
>
> 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
The primary EnergyPlus web site is found at:
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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.
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