Michael Wetter
Lawrence Berkeley National Laboratory, Energy Technologies Area, Building Technology and Urban Systems, Division, Simulation Research Group, Berkeley CA, USA
Marcus Fuchs
RWTH Aachen University, E.ON Energy Research Center, Institute for Energy Efficient Buildings and Indoor Climate, Aachen, Germany
Thierry S. Nouidui
Lawrence Berkeley National Laboratory, Energy Technologies Area, Building Technology and Urban Systems, Division, Simulation Research Group, Berkeley CA, USA
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http://dx.doi.org/10.3384/ecp1511831Published in: Proceedings of the 11th International Modelica Conference, Versailles, France, September 21-23, 2015
Linköping Electronic Conference Proceedings 118:3, p. 31-41
Published: 2015-09-18
ISBN: 978-91-7685-955-1
ISSN: 1650-3686 (print), 1650-3740 (online)
This paper discusses design decisions for exporting
Modelica thermofluid flow components as Functional Mockup Units.
The purpose is to provide guidelines that will allow
building energy simulation programs and HVAC equipment manufacturers
to effectively use FMUs for modeling of HVAC components and systems.
We provide an analysis for direct input-output dependencies of
such components and
discuss how these dependencies can lead to algebraic loops
that are formed when connecting thermofluid flow components.
Based on this analysis, we provide recommendations
that increase the computing efficiency of such components
and systems that are formed by connecting multiple components.
We explain what code optimizations are lost when providing
thermofluid flow components as FMUs rather than Modelica code.
We present an implementation of a package for FMU export
of such components, explain the rationale for selecting
the connector variables of the FMUs and finally provide
computing benchmarks for different design choices.
It turns out that selecting temperature rather than
specific enthalpy as input and output signals does not
lead to a measurable increase in computing time, but
selecting many small FMUs
rather than a large FMU considerably increases
computing time.
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