[esp-r] Re: Mysterious zone temperatures

[Jon Hand]

Use of operation file air flow to create mixing....

The question below uses ventilation between zones (specified
in the zone operations file) to force mixing. Note that this
will use the last known temperature of the source zone
in its calculations.  If you are using one timestep and hour
this might cause artifacts - one suggestion is to run the
simulation at a shorter timestep.

Another approach is to represent the flow via components
in a mass flow network.  Some users would prefer this
because it gives a bit more control and offers additional
reporting.

-Jon Hand
________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of Liam O'Brien [w_obrie at encs.concordia.ca]
Sent: 10 September 2009 02:55
To: esp-r at lists.strath.ac.uk
Subject: [esp-r]  Mysterious zone temperatures

Hi All,

I came across a strange phenomenon that I can't explain and I'm hoping
someone out there can.  I have a very basic model with two adjacent
cubic 1000 m^3 zones; one with a large glazing area, the other opaque.
They are otherwise thermally identical.  I am studying the effect of
different airflow rates between them.

I specified airflow in the opr files by having air flow from zone #1 to
zone #2 and the same quantity going the reverse direction,
simulataneouly, for mass balance.

What I would expect is: as the airflow rates approach some high level,
the zone air temperatures equalize at some temperature that is near the
average of the two when there is no airflow.

What I got: the temperatures do begin to equalize, but at some level
that is about 2-3C below expected.  This reprsents a lot of "missing"
energy.

I re-ran the model for airflow rates between 0 and 360 m^3/s.  The
unexpected results appear to occur around 30 m^3/s and above.

The same experiment using an airflow network yielded a similar conclusion.

I would be extremely grateful if someone could enlighten me.  Thanks
very much.

Liam O'Brien
PhD candidate
Concordia University




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