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Heat-transfer simulations applied to electrical machines

Time: Fri 2020-12-18 14.00

Location: Live-streaming via Zoom:, Stockholm (English)

Subject area: Engineering Mechanics Electrical Engineering

Doctoral student: Kristian Rönnberg , Teknisk mekanik

Opponent: Professor Jens Walther, Technical University of Denmark, Department of Mechanical Engineering

Supervisor: Christophe Duwig,

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Electrification and energy efficiency are two important aspects in present scenarios describing a sustainable future. Electric motors constitute a large fractionof industry’s electricity demand today, and it is expected to remain high inthe future. Electrification of the transport sector is expected in a sustainabledevelopment scenario, leading to a large increase in electric vehicles. Theirpropulsion systems will contain one or several motors.Development of new energy efficient motors and generators requires highresolution methods for studying and describing heat transfer phenomena. Thissince temperature level affects a motors efficiency and effective and efficientcooling allows for using less active material in the motor.In this work simulations of temperature distribution in a motor for tractionapplications are performed with different specifications of the loss distributionand distribution of coolant flow. Simulation results are compared to measuredvalues. The comparison shows how the simulation results differ in comparisonto the measurements. It can be concluded that attention needs to be paid tohow the simulation is defined when comparing to measured data.In establishing high resolution simulation approaches, the heat transfersystem constituting of an impinging jet on a flat plate is considered as aprototype problem. A Large-Eddy Simulation (LES) approach is employed tostudy the heat transfer and gather heat transfer data. Statistical analysis ofsampled heat transfer data shows behavior which is previously unpublished.The application of Proper Orthogonal Decomposition (POD), on the heattransfer field, and Extended Proper Orthogonal Decomposition (EPOD), linkingheat transfer modes with fluid flow modes, regarding the impinging jet systemis performed for the first time. The results show a clear correlation betweenstructures in the heat transfer field and structures in the fluid flow field.The investigated simulation methods and approaches can be employed instudies of heat transfer in electric machines.