[TRNSYS-users] Cooling loads... Strange results (energy balance)

[Thibaut VITTE]

David,

Thanks for your help.
I checked my schedules, and there is nothing specially correlated with 
the pikes. As I said, the pikes can appear on  different days, 
"depending" on minor changes in the simulation, and happen on different 
hours as well.
This is not a convergence problem in the TRNSYS solver, but i checked 
the energy balance, and I do have problems with that.
The energy balance is totally wrong (up to 2.15*10^6 kJ/hr) on these 
timesteps, and the Qtrans value goes from negative (which is normal, due 
to solar radiations) to positive (more than the opposite) in one time 
step. It can be seen on the surfaces' temperature that goes down for the 
timesteps where the loads are meaningless.

I think my problem comes from great coupling air flows (up to one third 
of a volume in one hour, I have virtual walls). Am I right ? Is there a 
way to avoid this, is there a parameter to tune to make the energy 
balances more precise ?

Thanks in advance.


David Bradley a écrit :
> Thibault,
>   Is it possible that there is a change in zone set point at those 
> times? Technically, there is an infinite load on the space when the 
> space temperature is changed by returning from a setback or setup 
> temperature. You should be able to tell if there is a convergence 
> problem by looking at the *.lst file - it will let you know whenever 
> the system didn't converge.
> Kind regards,
>  David
>
>
> Thibaut VITTE wrote:
>> Dear Trnsys Users,
>>
>> I'm working on a rather big building, and I have a strange behaviour, 
>> that I don't understand.
>> The cooling loads computed by Trnsys follow a normal pattern, except 
>> some days, for one or 2 points  that ar 3 to 4 times greater than the 
>> baseline.
>> I've attached a picture to explain it better.
>>
>> I've thought it was a bug in my inputs, so I tried to disable solar 
>> radiations, temperature, internal gains, I double checked my 
>> schedules, I... and I found nothing. Actually I found some minor 
>> errors, and they had an effect on the pattern (for example the 
>> "pikes" appear later in the year), but  the behaviour is still erratic.
>>
>> So, is it possible that a convergence problem (even though I have a 
>> 10^-3 tolerance convergence) makes this erratic behaviour ? It is a 
>> big building, with shading masks, internal windows, high coupling air 
>> flows (exactly in the zones that show the unexplainable loads), and 
>> the simulation takes a pretty long time.
>>
>> I Hope someone has some answer, because I really don't see!..
>>
>> Thanks in advance
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>
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>>   
>
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-- 
Thibaut Vitte
thibaut.vitte at h3c-energies.fr

H3C Energies
Services et Conseils en énergie
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