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 UsersI 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 helpKind regards,REAL ThomasIngénieur RechercheResearch Engineerreal-thomas@aldes.com
Tel : 05.61.24.95.65 - Fax : 05.61.24.95.69P Afin de contribuer au respect de l'environnement, merci de n'imprimer cet e-mail que si nécessaire.
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