Prediction and measurement of heat transfer in air-cooled disc-type electrical machines

Abstract

Index Terms-Axial flux permanent magnet machine, disc type machine, stator heat transfer, thermal analysis, CFD Abstract-Accurate thermal analysis of axial flux permanent magnet (AFPM) machines is crucial in predicting maximum power output. Stator convective heat transfer is one of the most important and least investigated heat transfer mechanisms and is the focus of this paper. Experimental measurements were undertaken using a thin-film electrical heating method, providing radially resolved steady state heat transfer data from an experimental rotor-stator system designed as a geometric mockup of a through-flow ventilated AFPM machine. The measurements are compared with computational fluid dynamics (CFD) simulations using both 2D axisymmetric and 3D models. These were found to give a conservative estimate of heat transfer, with inaccuracies near the edge and in the transitional flow regime. Predicted stator heat transfer was found to be relatively insensitive to the choice of turbulence model and the SST model was used for most of the simulations.

Thermal modeling for the design and check of an axial flux PM motor

“…On the other hand, as already discussed, (16)- (19) can give a fair estimate of the copper thermal state even by neglecting P pm .…”

Transient thermal modelling of an Axial Flux Permanent Magnet (AFPM) machine with model parameter optimisation using a Monte Carlo method

“…This depends on the presence of any interface materials and/or the contact condition between the surfaces. If an interface material is present, k' can be derived based on its thickness (t) and thermal conductivity (k) as shown in equation (6). However, the actual k' is still dependent on the surface roughness and contact pressure at the interface.…”

“…However, in order to achieve accurate predictions, the model parameters such as convective heat transfer coefficients, thermal contact resistances, and component geometries and properties must be determined accurately. These parameters can be determined by calculation, from the machine geometry, and by experimental measurements, such as the stator convective heat transfer coefficients recently measured by Howey et al [6]. However in practice there will always be uncertainty surrounding the exact model parameterisation and therefore empirical tuning is required.…”

Numerical modelling of an axial flux permanent magnet machine for convection heat transfer

“…Howey et al [5][6][7] have carried significant study on stator convective heat transfer from his experimental investigation for both flat rotor and rotor with protrusions. In his experimental measurements for a flat rotor, the transition from laminar to turbulent begins when the Re θ is higher than 3 × 10 5 and the flow regime become fully turbulent after Re θ is larger than 5 × 10 5 .…”