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Convergence behaviour of coupled pressure and thermal networks

Andreas Blaszczyk (ABB Corporate Research, Baden-Dättwil, Switzerland)
Reto Flückiger (ABB Corporate Research, Baden-Dättwil, Switzerland)
Thomas Müller (Fakultät für Informatik, I10 (LRR), Technische Universität München, Garching, Germany)
Carl-Olof Olsson (ABB Corporate Research, Västeras, Sweden)



The purpose of this paper is to present a method for thermal computations of power devices based on a coupling between thermal and pressure networks. The concept of the coupling as well as the solution procedure is explained. The included examples demonstrate that the new method can be efficiently used for design of transformers and other power devices.


The bidirectional propagation of temperature signal is introduced to the pressure network, which enables control of the power flow and a close coupling to the thermal network. The solution method is based on automatic splitting of the network definition (netlist) into two separate networks and iteratively solving the model using the Newton-Raphson approach as well as the adaptive relaxation enhanced by the direction change control.


The proposed approach offers reliable convergence behaviour even for models with unknown direction of the fluid flow (bidirectional flows). The accuracy is sufficient for engineering applications and comparable with the computational fluid dynamics method. The computation times in the range of milliseconds and seconds are attractive for using the method in engineering design tools.


The new method can be considered as a foundation for a consistent network modelling system of arbitrary thermodynamic problems including fluid flow. Such a modelling system can be used directly by device designers since the complexity of thermodynamic formulations is encapsulated in predefined network elements while the numerical solution is based on a standard network description and solvers (Spice).



Blaszczyk, A., Flückiger, R., Müller, T. and Olsson, C.-O. (2014), "Convergence behaviour of coupled pressure and thermal networks", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 33 No. 4, pp. 1233-1250.



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