Re: [EnergyPlus_Support] Model Underfloor Air Distribution?

["Qiang \(Peter\) Zhang" <peter@xxxxxxxxxxxxxxxxx>]

I did my Master thesis on UFAD modeling of indoor stratification and some
testing result I did in a Chamber in St. Louis was published on ASHRAE
JOURNAL, although my name was not shown in the paper.
The model still has some holes in it, like the window plume simulation in a
perimeter zone. But, one basic thermal plume model is discussed in quite a
detail, which is the main driving force of moving air from lower zone to
upper zone. I also tried to model upper/lower zones separately, but the
model was not quite successful at differentiating core and perimter zones.
The typical pattern of vertical temp profile in a core zone is that you get
a large gradient at the bottom and at an almost uniform upper zone. The
smoke test of swirl diffusers shown the quick spreading of cool air all over
the floor. While the pattern of a perimeter zone is largely influenced by
the window walls, which creates a large gradient in the upper zone, while
lower zone is close to be uniform due to the stronger radiation onto the
floor.

Regarding the benefit of the system, testings observed that:
1. Overhead Lights almost makes no difference in the indoor temperature
profile. In other words, you probably can cut this out of your air load
calculation.
2. One perimter zone test shows that supply and return air temp difference
can reach 30F, with 65 in and 95 out. I didn't feel much discomfort.

On the load calculation, you really need to separate supply air load (the
amount of conditioned air to counteract the lower zone heat gain) from
chiller load, which takes care of the whole building heat gain. Of course,
depending on the arrangement of economizers.

Peter

----- Original Message -----
From: "TangoJim" <TangoJim@xxxxxxxxx>
To: <EnergyPlus_Support@xxxxxxxxxxxxxxx>
Sent: Friday, July 26, 2002 8:44 AM
Subject: Re: [EnergyPlus_Support] Model Underfloor Air Distribution?


> Could you use the MIXING command in E+ to achieve the
> transfer of air from a lower zone (with a height about
> 5 feet) to the upper zone (with the remaining height
> of the room)? Most of the overhead light energy should
> be assign to the upper zone. I would think some of the
> equipment and people (radiation) energy should also be
> assign to the upper zone as well. The solar radiation
> from the windows in the upper zone could be simulated
> using an interior upper floor glazing. This will allow
> the solar radiation be absorbed by the lower zone.
>
> The lower zone would be a conditioned space
> controlling the supply air temperature and the upper
> zone would be an un-conditioned space with air
> transferred to it from the lower zone.
>
> From my understanding of underfloor air distribution
> systems, people are comfortable with a supply air
> temperature of around 65 degree F. The ceiling return
> air temperature is much higher, about 85 degree F. I
> would think this system would extend the time period
> of an outside economizer and also reduce the amount of
> dehumidification from the cooling coils.
>
> I have been thinking of how to simulate this situation
> for sometime. I am planning to experiment with this
> model further.
>
> James Trowbridge
> Director of Research & Development
> Taylor Systems Engineering
>
>
>
> --- "Richard J. Liesen" <r-liesen@xxxxxxxx> wrote:
> > It is possible to model the underfloor air
> > distribution in EnergyPlus.  At
> > this time it is NOT possible to include the
> > stratified air, and the
> > transfer of the warm stratified to perimeter zones
> > above.
> >
> > Thanks Richard Liesen
> >
> >
> > At 02:43 PM 7/26/2002, mtagles wrote:
> > >Is it possible to model underfloor air destribution
> > with E+,
> > >including stratified air, and the transfer of the
> > warm stratified to
> > >perimeter zones above?
> > >
> > >If not E+, any suggestions?
> > >
> > >Thanks in advance.
> > >
> > >Michael Tagles.
> > >
> >
> >
> >
>
>
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