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TRNSYS documentation recommends a multiplication factor of 5-10xAir capacitance for a furnished air node. ASRAE, European standards recommend adjusting the capacitance of furnished Airnode based on model calibration (capacitance of furniture to minimize RMSE of simulation and observed zone temperature). Is there anyway to dynamically change the capacitance of an airnode and find the optimum one using algorithms available in TRNOPT? To my knowledge air node capacitance in TRNSYS cannot be dynamically changed. Any comments on this will be highly appreciated. Thanks.
TimMcDowell 06/06/2023 3:59 pm
@tm-abir-ahsan Since the zone capacitance cannot be exposed as an input to the Type56 building model it cannot be changed by TRNOpt. There are other optimization options available (like using GenOpt directly or Python scripting) that involve modifying the building input file directly and running the simulations. These processes take a deep knowledge of the structure of the building input file (see the Multizone Building volume of the TRNSYS documentation set) and how the optimization processes modify files and execute simulations. A first step would be to run your simulation at a high and low value of capacitance and see how those results compare to your measured temperatures. This may lead you to conclusions on the capacitance without needing a full blown optimization.
Hi Tim, Thanks for your help. I would request TRNSYS to include this modification so that users can calibrate their model which I believe is a common practice.
DavidBradley 16/06/2023 3:09 pm
@tm-abir-ahsan
There is a model of a lumped capacitance in the TESS Loads and Structures library (Type963). It can be coupled to Type56 to model a varying amount of thermal capacitance in a zone and because it is its own Type, it can also be exposed to TRNOpt.
kind regards,
David
Hi David, That was super helpful. Thank you so much, I will use that one then!
