Internal Solver and User Interface for TRNFLOW

Due to the integration of the air flow model into Type 56 the TRNSYS Solver can no longer be used for the iteration process between the two models. A into Type56 integrated solver is used to reach convergence. Depending on the boundary conditions the coupling of the two models forms a recursive flow of information with negative feedback. E. g. at cold outdoor air an increasing indoor temperature imposes an increasing exchange of air. In turn this counters another increase of the indoor temperature so that a balance will appear (Fig. 4). If the negative feed back gets too strong there will be the risk of getting an unstable system. A solver algorithm with a successive substitution method (TRNSYS solver 0) then also becomes unstable. Therefor the new solver integrated into Type 56 automatically dampens individually every recursive flow of information according to the iteration process so that an optimum of stability and convergence is achieved.

For TRNFLOW the functionality of PREBID has been enlarged. Beneath traditional data of the thermal model also the required input information of the air flow model can be entered into the new PREBID 5. This data is also stored in the BUI file and can be read in from it again. Analog to the Standard Type 56 files (TRN, BLD) the new PREBID 5 also creates a COMIS Input File (CIF) which is read by TrNfLOW. The CIF created this way is — with few additions — completely equivalent to the format described in the COMIS 3.1 User’s Guide [4] Unlike to former simulations with COMIS the COMIS Input File (CIF) is now checked to be consistent with the thermal model (bui-file).