[esp-r] Re: Mysterious zone temperatures

[Liam O'Brien]

Hi Jon,

You hit the nail on the head.  However, I had tried to use an airflow  
network for the same purpose and increasing the timesteps/hour also  
effected results - a lot.  I need about 10/hour for the solutions to  
converge.

Thanks for the tips.

Liam

Quoting Jon Hand <jon at esru.strath.ac.uk>:

>
> 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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