New links with external programs: EES[5], Excel or Matlab

New Types that link TRNSYS with EES, Excel or Matlab are now available in TRNSYS 16. To allow for such models to be included in TRNSYS simulations it was necessary to create components in the TRNSYS code that explicitly link to the external programs, execute the models and provide some method of data transfer between the programs. These components work by having TRNSYS call the external program at each iteration. Especially the link to Excel is really a powerful feature cause it allows to communicate in a TRNSYS- Simulation quite easy with real system components like a controller over the Excel API — Interface like it was shown in [6].

Improved numerical precision and "time definition"

All variables in TRNSYS16 are now double precision numbers. This leads to an improved numerical accuracy, which is measurable for example by the very small time steps achievable in TRNSYS 16 (down to 1/100th of a second). This allows to simulate the real behavior of controllers Programming new Types is also easier thanks to the consistent use of double precision.

Enhancements to the TRNSYS solver

A new numerical solver has been added to TRNSYS. The new solver is intended to replace the default solver (successive substitution) in special cases with a strong feedback without a sufficient capacity in the system. A typical case is natural ventilation simulation, where a strong coupling exists between temperature and airflows. The new TRNSYS solver is hence similar to the solver implemented by EMPA in TRNFLOW, the extended Type 56 with integrated airflow modeling.

Other usability enhancements

The equations can now be declared in any order in a TRNSYS input file. New functions have also been added to TRNSYS equation processor The TRACE command can be used for equations

Equation solving can now be done to within a TOLERANCE instead of being absolute, aiding significantly in convergence.

A timer routine is available to identify the routines where TRNSYS spends most of the simulation time

Conclusions

TRNFLOW is a tool which allows an easy calculation of natural ventilation, passive night cooling, double facades and exhaust air shafts quite fast.

No new input file structure or user interface has to be learned. Using PREBID 5 simply the known user-friendly user interface has been expanded.

The newly-developed internal solver is featured with high stability. Due to integrated automatically optimization of convergence the user is no longer bothered with numerical questions.

In TRNSYS version 16, the capability of TRNSYS to adapt to new types of simulation problems has been pushed beyond new limits: Writing a component in any programming, copying the DLL provided by the model author onto the hard disk is sufficient to run it! Several new Types have been added, including a type for the link between TRNSYS and Matlab as well as a link to EXCEL. The window model of the building has been improved and treats now visible and nonvisible sunlight according to the spectral data of the window. A model for chilled ceilings has been added to the building.

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