[TRNSYS-users] Time steps on Studio (deck) and Build

[David Bradley]

Thomas,
  The value to which you refer in TRNBuild is called a time base and it 
is not quite the same thing as a time step. TRNBuild takes the walls 
that you define and it applies an algorithm to them that results in the 
calculation of a series of coefficients. Each coefficient is really a 
weighting factor that tells how important a given factor (such as the 
temperature difference across the wall, or the energy transfer through 
the wall) was at a given point in the history of the wall. Normally, the 
first coefficient determines how important the factor is at the current 
time, the second coefficient determines how important the factor was one 
hour ago, the third one determines how important the factor was two 
hours ago, etc. For walls that are very massive or very lightweight, you 
can imagine that the method would break down - if the entire response of 
the wall occurs within the past 15 minutes, it will not be accurately 
modeled if there are coefficients only for each hour back in history. 
The time base in TRNBuild allows you to adjust the frequency of the 
coefficient calculation; if you indicate that the time base is 2 hours 
instead of 1, you can simulate more massive walls because the history 
covered by the coefficients will extend farther back in time. The only 
rule is that the TRNSYS simulation time step cannot be greater than the 
Type56 / TRNBuild time base.
Kind regards,
 David


Real Thomas wrote:
> Dear TRNSYS Users
>  
> I have just discovered there is a time step in TRNBUILD which is 
> different from the time step in the Studio (deck).
> I had run a lot of simulations with a TRNBUILD time step of 1 hour 
> and a Studio time step really lower (30 seconds, 1 minute, 5 
> minutes ) . These simulations seemed quite good and worked well if we 
> put an Input Value Recall (Type 93) between the Building outputs and 
> some other components.
>  
> I have now changed the time step in TRNBUILD (0.1 hour => I couldn't 
> go lower) and changed the Studio time step to 0.1 hour.
> I can see differences, but they are not big : less than 2% for a total 
> consumption of the year.
>  
> The problem is that I am studying strategies of heating regulations. 
> So, I need short time steps to see if my regulation strategy is good.
>  
>  
> I have 2 questions :
>  
> - Do you think my simulations already run with different time steps 
> between TRNBUILD and the Studio are wrong ? not realist ?
>  
> - If the time steps of the Studio is lower than the TRNBUILD time 
> step, what information / instructions are given by the studio to 
> TRNBUILD ?
> For exemple I have calculated with the Studio every minute the air 
> temperature to blow into a room in the Studio, the TRNBUILD time step 
> is 1h : what is the air temperature used in TRNBUILD : the mean of the 
> temperatures calculated every minutes ? only the temperature 
> calculated at 60 minutes ? or an other one ?
>  
> Thank you for your help
>  
> Kind regards,
>  
> *REAL Thomas*
> Ingénieur Recherche
> Research Engineer
> real-thomas at aldes.com <mailto:real-thomas at aldes.com>
> Tel : 05.61.24.95.65 - Fax : 05.61.24.95.69
> www.aldes.com <http://www.aldes.com/>
>  
> P */Afin de contribuer au respect de l'environnement, merci de 
> n'imprimer cet e-mail que si nécessaire./*
>
> ------------------------------------------------------------------------
>
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-- 
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Thermal Energy System Specialists (TESS), LLC 
David BRADLEY                      2916 Marketplace Drive - Suite 104 
Partner                            Madison, WI 53719 
                                   USA
P: +1.608.274.2577 
F: +1.608.278.1475
E-mail: bradley at tess-inc.com 
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