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AW: [EnergyPlus_Support] Division of one zone into several sub-zones
Celine,
I have already thought of dividing on zone into sub zones and come to
the following conclusion:
1. The zone separation has to be by a light weight and low resistance
wall so that heat transfer between sub zones is maximised.
2. With the COMIS link also air exchange can be realised.
Problems:
1. How to specify internal loads? Is it possible to specify the exact
load for each sub zone or would you have to divide the whole room load
into sub loads by a factor that corresponds to the volume ratio of the
sub zone and the whole zone.
2. Separation Walls: As they are defined as low mass walls, they cannot
store energy, so the room temperature in the sub zone is more likely to
oscillate in comparison to looking at the temperature of the whole zone.
3. Surface temperatures will be different as heat transfer coefficients
will change by the influence of a separation wall.
4. What to do with windows? There will be an incredible solar load in a
sub zone with a window in comparison to one without. Solar radiation
will be absorbed by sub surfaces and their temperature will rise much
higher than in other sub zones.
There might be the possibility defining a division wall as window. But I
am not sure if solar radiation also passes through a second window.
5. You might overcome the problem of defining a general HVAC system for
the whole zone, when equipping sub zones with decentralised units. But
what to do if there is only one system for the whole zone? It would not
be sensible to divide it into sub systems.
On the whole, I am not sure if dividing zones can produce reasonable
results.
If you have come the any sensible solution, I would be grateful if you
let me know.
Alexander
_______________________________________
DI (FH) Alexander Beisteiner
Wissenschaftlicher Mitarbeiter
Forschungs- und Technologietransfer Pinkafeld GmbH
Steinamangerstraße 21
A - 7423 Pinkafeld
Tel.: +43-3357-45370 DW 1324
Fax.: +433357-45370 DW 1010
-----Ursprüngliche Nachricht-----
Von: Celine Weber [mailto:celine@xxxxxxxxxxxxxxxxxxxxxxx]
Gesendet: Mittwoch, 02. April 2003 05:02
An: EnergyPlus_Support@xxxxxxxxxxxxxxx
Betreff: [EnergyPlus_Support] Division of one zone into several
sub-zones
Hello,
We are using Energy Plus to develop some realistic heating and
cooling demand profiles for large office buildings in Tokyo.
For the large open work areas that are common here, large
temperature gradients can develop across the room from the
location of the main heating/cooling vent to the windows. So it
is common practice to add small package air conditioners to
provide supplementary heating and cooling near the windows. In
order to model the relative energy requirements for the main
and supplementary air conditioning systems in Energy Plus, we
are trying to use a method of dividing the large room into
several zones that are divided by "virtual walls". We want to
use the COMIS package to model the free convection of air
between those zones.
Has anyone tried anything similar with Energy Plus - i.e. dividing
single rooms into two or more zones and using MIXING objects or COMIS
to generate convection? We would be grateful for a chance to learn
about new ways to do this and/or swap experiences with failures and
trying to overcome them.
Celine Weber
University of Tokyo
Department of Chemical Systems Engineering
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