Re: [EnergyPlus_Support] How many zones for a VAV system

["Michael J. Witte" <mjwitte@xxxxxxxx>]

For this application, I would create three plenum zones, North, South and 
Center plenum to model the ceiling space(s) in these three areas.  Use each of 
these as a return plenum for the packaged unit serving that zone.  If the three 
zones are controlled to the same setpoints, there is little impact from a 
modeling perspective of combining the three flows in the vertical shaft.  If 
you expect the three plenum areas to be at different temperatures, then you 
could add some CROSS MIXING objects to mix the plenum zones.  You cannot model 
the combined flow within the air loop simulations.

Mike


On 17 Jan 2008 at 9:34, ooikoonbeng2004 wrote:

> Dear all, 
> 
> i would like to how to model the ceiling space, space between ceiling 
> and the floor of the next storey, that is being used as space for the 
> return air, to a vertical return air shaft in the center of a multi- 
> storey building, to unitary (packaged) air conditioning units at the 
> roof top. 
> 
> i need to know this as i do not know what to input in the  
> OutsideFaceEnvironment of the ceilings, and floors, of the three zones 
> (North, South and Center) of the four stories of this building that is 
> being supplied by three packaged air conditioning units at the roof top
> 
> The air from the three zones return through the common vertical return 
> air shaft. A variable speed drive fan supplies the Variable Air 
> volumes for each zone. Each floor of the building is divided into 
> three zones, South, Central, and North.  These three zones of the four 
> floors are connected vertically to four systems, unitary (packaged) 
> air conditioning units with one fan and many compressors each, on the 
> roof. The North zone is exposed to more sun load, and is therefore fed 
> with two units.  Since each floor is fed with conditioned air from 
> three systems, a single system failure will not make a floor devoid of 
> air-conditioning. The overall reliability is thus very high. 
> 
> This rectangular building has 51.8m width, mostly glass, facing North 
> and South. Each upper floor overhangs 1.6m of the lower floor to 
> provide shade.   
> 
> How many zones do in need in my model? 
> 
> Much obliged,
> ooi
> 
> 
> 
> 
> 
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> 
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> 
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> 
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> 
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> 
> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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