Simplifications for hydronic system models in modelica
Abstract
Building systems and their heating, ventilation and air conditioning flow networks, are becoming increasingly complex. Some building energy simulation tools simulate these flow networks using pressure drop equations. These flow network models typically generate coupled algebraic nonlinear systems of equations, which become increasingly more difficult to solve as their sizes increase. This leads to longer computation times and can cause the solver to fail. These problems also arise when using the equationbased modelling language Modelica and Annex 60based libraries. This may limit the applicability of the library to relatively small problems unless problems are restructured. This paper discusses two algebraic loop types and presents an approach that decouples algebraic loops into smaller parts, or removes them completely. The approach is applied to a case study model where an algebraic loop of 86 iteration variables is decoupled into smaller parts with a maximum of five iteration variables.
 Authors:

 Univ. of Leuven (Belgium); EnergyVille, Genk (Belgium)
 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
 Publication Date:
 Research Org.:
 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
 Sponsoring Org.:
 USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office
 OSTI Identifier:
 1437004
 Grant/Contract Number:
 AC0205CH11231
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Journal of Building Performance Simulation
 Additional Journal Information:
 Journal Volume: none; Journal Issue: none; Journal ID: ISSN 19401493
 Publisher:
 Taylor & Francis
 Country of Publication:
 United States
 Language:
 English
 Subject:
 42 ENGINEERING
Citation Formats
Jorissen, F., Wetter, M., and Helsen, L. Simplifications for hydronic system models in modelica. United States: N. p., 2018.
Web. https://doi.org/10.1080/19401493.2017.1421263.
Jorissen, F., Wetter, M., & Helsen, L. Simplifications for hydronic system models in modelica. United States. https://doi.org/10.1080/19401493.2017.1421263
Jorissen, F., Wetter, M., and Helsen, L. Fri .
"Simplifications for hydronic system models in modelica". United States. https://doi.org/10.1080/19401493.2017.1421263. https://www.osti.gov/servlets/purl/1437004.
@article{osti_1437004,
title = {Simplifications for hydronic system models in modelica},
author = {Jorissen, F. and Wetter, M. and Helsen, L.},
abstractNote = {Building systems and their heating, ventilation and air conditioning flow networks, are becoming increasingly complex. Some building energy simulation tools simulate these flow networks using pressure drop equations. These flow network models typically generate coupled algebraic nonlinear systems of equations, which become increasingly more difficult to solve as their sizes increase. This leads to longer computation times and can cause the solver to fail. These problems also arise when using the equationbased modelling language Modelica and Annex 60based libraries. This may limit the applicability of the library to relatively small problems unless problems are restructured. This paper discusses two algebraic loop types and presents an approach that decouples algebraic loops into smaller parts, or removes them completely. The approach is applied to a case study model where an algebraic loop of 86 iteration variables is decoupled into smaller parts with a maximum of five iteration variables.},
doi = {10.1080/19401493.2017.1421263},
journal = {Journal of Building Performance Simulation},
number = none,
volume = none,
place = {United States},
year = {2018},
month = {1}
}
Web of Science
Figures / Tables:
Works referenced in this record:
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journal, February 2013
 NytschGeusen, Christoph; Huber, Jörg; Ljubijankic, Manuel
 Bauphysik, Vol. 35, Issue 1
Modelica Buildings library
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 Wetter, Michael; Zuo, Wangda; Nouidui, Thierry S.
 Journal of Building Performance Simulation, Vol. 7, Issue 4
DepthFirst Search and Linear Graph Algorithms
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 Tarjan, Robert
 SIAM Journal on Computing, Vol. 1, Issue 2
Depthfirst search and linear graph algorithms
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 Tarjan, Robert
 12th Annual Symposium on Switching and Automata Theory (swat 1971)
Works referencing / citing this record:
Model implementation and verification of the envelope, HVAC and controller of an office building in Modelica
journal, December 2018
 Jorissen, F.; Boydens, W.; Helsen, L.
 Journal of Building Performance Simulation, Vol. 12, Issue 4
Figures / Tables found in this record: