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Re: [EnergyPlus_Support] Zone components of a 2-pipe system?
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.
>
>
>
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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