Comparison of Moving Boundary and Finite-Volume Heat Exchanger Models in the Modelica Language†Report as inadecuate




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1

Thermodynamics laboratory, University of Liege, Campus du Sart Tilman, B-4000 Liege, Belgium

2

IPU Engineering Consultant, DK-2800 Kongens Lyngby, Denmark

3

Department of Flow heat and combustion Mechanics, University of Gent, 9052 Gent, Belgium



This paper is an extended version of our paper published in Desideri, A.; Wronski, J.; Dechesne, B.; van den Broek, M.; Gusev, S.; Quoilin, S.; Lemort, V. Comparison of moving boundary and finite-volume heat exchanger models in the Modelica language. In the Proceedings of the 3rd International Seminar on ORC Power Systems, Brussels, Belgium, 12–14 October 2015.





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Author to whom correspondence should be addressed.



Academic Editor: Tariq Al-Shemmeri

Abstract When modeling low capacity energy systems, such as a small size 5–150 kWel organic Rankine cycle unit, the governing dynamics are mainly concentrated in the heat exchangers. As a consequence, the accuracy and simulation speed of the higher level system model mainly depend on the heat exchanger model formulation. In particular, the modeling of thermo-flow systems characterized by evaporation or condensation requires heat exchanger models capable of handling phase transitions. To this aim, the finite volume FV and the moving boundary MB approaches are the most widely used. The two models are developed and included in the open-source ThermoCycle Modelica library. In this contribution, a comparison between the two approaches is presented. An integrity and accuracy test is designed to evaluate the performance of the FV and MB models during transient conditions. In order to analyze how the two modeling approaches perform when integrated at a system level, two organic Rankine cycle ORC system models are built using the FV and the MB evaporator model, and their responses are compared against experimental data collected on an 11 kWel ORC power unit. Additionally, the effect of the void fraction value in the MB evaporator model and of the number of control volumes CVs in the FV one is investigated. The results allow drawing general guidelines for the development of heat exchanger dynamic models involving two-phase flows. View Full-Text

Keywords: organic Rankine cycle ORC; dynamic modeling; dynamic validation; Modelica organic Rankine cycle ORC; dynamic modeling; dynamic validation; Modelica





Author: Adriano Desideri 1,* , Bertrand Dechesne 1, Jorrit Wronski 2, Martijn van den Broek 3, Sergei Gusev 3, Vincent Lemort 1 and Sylvain Quoilin 1

Source: http://mdpi.com/



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