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How is the Occupied Subzone Load calculated in UFAD system?

asked 2016-08-22 08:27:06 -0500

Byeongho's avatar

updated 2016-08-22 11:10:08 -0500

In EnergyPlus simulation, I want to know how is the Occupied Subzone load calcuated in UFAD system clearly such as calculation proceedure, affecting factor and ect. I think, actually, the Occupied subzone is affected by Non-occupied subzone, radiation from ceiling surface and ect. In order to know that, what should i refer to?

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answered 2016-08-22 17:12:02 -0500

updated 2016-08-23 02:29:39 -0500

The under-floor air distribution model is covered in the Alternative Modeling Processes section of the Engineering Reference. Details are given in the implementation section.

It's not entirely clear to me which internal gains are applied in the occupied zone (presumably this is where People objects are located, and which in the upper zone (presumably most if not all Lights objects). It looks like that is up to the user to set via a gains fraction schedule for the occupied zone.

On heat transfer, heat is exchanged via radiation from the upper subzone ceiling to the lower subzone via an IRT surface or surfaces between them. This is described in the section on Infrared Transfer Materials. It should be noted that any short-wave radiation (light) will be converted to long-wave radiation (heat) as it passes through this object, and so any lighting results will not be calculated correctly if an IRT surface is present.

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Thank you for your answer. According to the Engineering Reference, the IR radiation can be exchanged but convective heat transfer is ignored since the convective heat gain coefficient is set to 0. and when the room air is returned, the airflow from lower zone to upper zone is possible. right? Therefore, when the lower zone load is calculated, except the ceiling(virtual surface between subzones), just convective heat gains of walls and floor are involved. Consquantly, the upper subzone condition can not influence on the lower subzone load. right?

Byeongho's avatar Byeongho  ( 2016-08-23 05:22:27 -0500 )edit

I would assume that when it says "Call subroutine HcUCSDUF to calculate a convective heat transfer coefficient for each surface in the zone", that the IRT surface is included in that calculation and so convective heat is transferred through it as though it were conductive heat.

Jamie Bull's avatar Jamie Bull  ( 2016-08-23 07:08:15 -0500 )edit

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Last updated: Aug 23 '16