Vince,

>     According to your solution for the modelling of atrium:
>
> >>    Taking all these objections together, I conclude that your best
> plan
> >>for getting reasonable answers is as follows: (1) model the atrium
> as a
> >>single zone; (2) use COMIS to find the zone-to-zone flows; (3) let
> >>TRNSYS determine the heat balance in the atrium; (4) if TRNSYS does
> not
> >>provide it, use a CFD or correlation model to estimate the resulting
> >>density distribution in the atrium; then (5) enter the new density
> >>distribution in the COMIS input file, then re-run COMIS. Repeat
> until
> >>you converge to a solution (which probably will take four or five
> major
> >>iterations at most).
>
>    I am not quite sure about step (5). In (5), do I need to separate
> the atrium into several imaginary levels and give each imaginary zones
> different temperatures? Or simply, how to feed COMIS with the density
> distribution in the atrium?

COMIS has, or used to have, an input section called &-NET-ZL (zone
layers). This section allows you to prescribe variations of
temperature (and pollutant concentration) with height inside a single
zone. I believe that the temperature profile is expressed in terms of
gradients from a given value, which can change dynamically with time.

When finding the pressure drops across each flow element (as part of
the airflow calculations), COMIS will honor the temperature profile
described there.

>    Furthermore, this solution is only for a given external condition.
> If the condition is changing, (such as an annual weather data), do you
> have any good solutions to simulate the atrium?

No, I do not have any good solution to the problem of dynamic changes
in the profile itself. Sorry.

If anybody else on the board has an idea about this, please help us out
here!

-Dave