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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 2-D axisymmetric and 3-D 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 used in the CFD simulations. © 2011 IEEE.

Thermal design and management of electric machines is important for achieving higher specific power outputs and, the heat transfer in the air gaps within them require further study. Research into convective heat transfer in the gaps between the rotor and the stator has generally centered on the rotor due to interest from turbomachinery applications. This paper focuses on rotating electric machines by investigating the stator heat transfer for an idealised disk type electric machine geometry. Experiments were carried out using a thin film heating system to provide radially resolved, steady-state heat transfer data for a number of gap ratios, rotational speeds and superposed in- and out-flow rates. Results were used to provide correlations for use in analytical models and were compared with a 2D axisymmetric CFD model using the SST turbulence model. Predictions were found to agree well with local heat transfer measurements, but did not well predict the effects of ingress at the periphery.

Relatively little fundamental research has been undertaken on heat transfer in disc type electrical machines, a common example being the axial flux permanent magnet (AFPM) machine. Power density is usually thermally limited and therefore understanding of stator convective heat transfer is crucial in the design of AFPM machines and electrical machines in general. This paper presents direct measurements of radially resolved stator convective heat transfer in a rotor-stator system, using a thin-film electrical heater array to measure heat transfer. The heater array combines surface temperature sensing with heat flux measurement. It is found for the three gap sizes considered here that average Nusselt number (non-dimensional convective heat transfer coefficient) increases from Nu (approximately equals) 100 at low disc speeds/rotational Reynolds numbers (Re = 3:7e4) up to Nu (approximately equals) 300 400 at higher speeds (Re = 5:6e5).

The modelling, simulation, fabrication and testing of a microchannel cooling plate are described in this article. The device is to be used in microelectronic packaging cooling applications. The nickel-based micro-channel cooling plate is fabricated on a glass substrate using a two-layer electroforming process borrowed from the UV-LIGA (UV-lithography, electroforming, replication) process. Forced convection of air or liquid is scheduled for this microchannel plate. The cooling plate has been tested using a custom-made rig to measure the flow pressure head as a function of mass flow rate. Hydraulic performance of the cooling plate is presented

We have developed a MEMS power conversion device that combines an axial-flow turbine with an axial-flux electromagnetic generator. This device can generate electrical power when placed in an air-stream, and is aimed at applications such as flow sensing and power generation for remote sensors. Recent experimental performance data are presented for prototypes, and compared with CFD (computational fluid dynamics) simulations. The current devices have a volume of approximately 0.5 cm/sup 3/, generate 1 mW of output power at a pressure drop of 8 mbar and a flow rate of 35 litres per minute, and will operate at pressure drops down to a few mbar.