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Is there a way to model "proper" control of a UFAD system in EnergyPlus?

asked 2018-12-17 11:16:08 -0500

updated 2019-01-22 14:20:25 -0500

It appears that EP models of UFAD systems control zone conditioning in a manner very similar to a VAV system; when a zone is in need of conditioning, airflow is increased to that zone at a fixed supply air temperature. AirTerminal:SingleDuct:VAV:Reheat:VariableSpeedFan objects are used as zone air terminal objects. The distinguishing feature of UFAD models in EP seems to be the use of the RoomAirSettings:UnderFloorAirDistributionInterior/Exterior objects to model the stratification effect of UFAD.

In practice, "proper" UFAD system control is to modulate the supply air temperature based on zone demands and keep air flow/plenum pressure constant, at least for a single large interior zone with similar internal gains and served by a single AHU. Is there way to do this in EP, or other program, without using something like a custom solution based on a supply air temperature reset via SetpointManger objects?

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answered 2018-12-31 09:11:20 -0500

You are correct that the RoomAirSettings:* objects define the UFAD characteristics for the thermal stratification model. Any type of HVAC system can be used with the UFAD model. If I understand correctly, for your application, you would use AirTerminal:SingleDuct:ConstantVolume:NoReheat. For single-zone system, the easiest approach would be to use AirLoopHVAC:UnitarySystem with "Control Type" = Load. This system type accepts any type of heating and cooling coil.

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Asked: 2018-12-17 11:16:08 -0500

Seen: 197 times

Last updated: Dec 31 '18