CFD Study of Forced Air Cooling and Windage Losses in a High Speed Electric Motor


High speed and high efficiency synchronized electric motors are favored in the automotive industry and turbo machinery industry worldwide because of the demands placed on efficiency. Herein an electric motor thermal control system using cooling air which enters from the drive end of the motor and exits from the non-drive end of the motor as the rotor experiences dissipates heat is addressed using CFD. Analyses using CFD can help to find the appropriate mass flow rate and windage losses while satisfying temperature requirements on the motor. Here, the air flow through a small annular gap is fed at 620 L/min (0.011 kg/sec) as the rotor spins at 100,000 rpm (10,472 rad/sec) and the rotor dissipates 200 W. The CFD results are compared with experimental results. Based upon the CFD findings, a novel heat transfer correlation suitable for large axial Reynolds number, large Taylor number, small annular gap Taylor-Couette flows subject to axial cross-flow is proposed herein.

Share and Cite:

Anderson, K. , Lin, J. , McNamara, C. and Magri, V. (2015) CFD Study of Forced Air Cooling and Windage Losses in a High Speed Electric Motor. Journal of Electronics Cooling and Thermal Control, 5, 27-44. doi: 10.4236/jectc.2015.52003.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Gardiner, S. and Sabersky, R. (1977) Heat Transfer in an Annular Gap. International Journal of Heat and Mass Transfer, 21, 1459-1466.
[2] Haddadi, S. and Poncet, S. (2008) Turbulence Modeling of Torsional Couette Flows. International Journal of Rotating Machinery, 2008, Article ID: 635138.
[3] Poncet, S. and Schiestel, R. (2007) Numerical Modeling of Heat Transfer and Fluid Flow in Rotor-Stator Cavities with Through Flow. International Journal of Heat and Mass Transfer, 50, 1528-1544.
[4] Poncet, S., Haddadi, S. and Viazzo, S. (2011) Numerical Modeling of Fluid Flow and Heat Transfer in a Narrow Taylor-Couette-Poiseuille System. International Journal of Heat and Fluid Flow, 32, 128-144.
[5] Poncet, S., Viazzo, S. and Oguic, R. (2014) Large Eddy Simulations of Taylor-Couette-Poiseuille Flows in a Narrow- Gap System. Physics of Fluids, 26, 105-108.
[6] Kuosa, M., Sallinen, P. and Larjola, J. (2004) Numerical and Experimental Modeling of Gas Flow and Heat Transfer in the Air Gap of an Electric Machine. Journal of Thermal Sciences, 13, 264-278.
[7] Murata, A. and Iwamoto, K. (2011) Heat and Fluid Flow in Cylindrical and Conical Annular Flow-Passages with Through and Inner-Wall Rotation. International Journal of Heat and Fluid Flow, 32, 378-391.
[8] Jeng, T.M., Tzeng, S.C. and Lin, C.H. (2007) Heat Transfer Enhancement of Taylor-Couette-Poiseuille Flow in an An- nulus by Mounting Longitudinal Ribs on the Rotating Inner Cylinder. International Journal of Heat and Mass Transfer, 50, 381-390.
[9] Dubrulle, B. and Hersant, F. (2002) Momentum Transport and Torque Scaling in Taylor-Couette Flow from an Analogy with Turbulent Convection. The European Physical Journal B, 26, 379-386.
[10] Hwang, J.Y. and Yang, K.S. (2004) Numerical Study of Taylor-Couette Flow with and Axial Flow. Computers & Fluids, 33, 97-118.
[11] Fenot, M., Bertin, Y., Dorignac, E. and Lalizel, G. (2011) A Review of Heat Transfer between Concentric Rotating Cy- linders with or without Axial Flow. International Journal of Thermal Sciences, 50, 1138-1155.
[12] Tzeng, S.C. (2006) Heat Transfer Is a Small Gap between Co-Axial Rotating Cylinders. International Communications in Heat and Mass Transfer, 33, 737-743.
[13] Seghir-Ouali, S., Saury, D., Harmand, S., Phillipart, O. and Laloy, D. (2006) Convective Heat Transfer inside a Rotating Cylinder with an Axial Air Flow. International Journal of Thermal Sciences, 45, 1166-1178.
[14] STAR CCM+ Users Manual.
[15] Patankar, S. (1980) Numerical Heat Transfer and Fluid Flow. Hemisphere Publishing Corporation, Washington DC and McGraw-Hill, New York.
[16] Anderson, K.R. (2004) CFD Analysis of Inlet and Outlet Regions of Coolant Channels in an Advanced Hydrocarbon Engine Nozzle. Proceedings of the 15th Annual Thermal and Fluids Analysis Workshop, TFAWS-04, Pasadena, 30 August-3 September 2004.
[17] White, F. (1974) Viscous Fluid Flow. McGraw Hill, New York.
[18] Wilcox, D. (1998) Turbulence Modeling for CFD. 2nd Edition, DCW Industries Inc., La Cañada Flintridge.
[19] Menter, F. (1994) Two Equation Eddy-Viscosity Turbulence Modeling for Engineering Applications. AIAA Journal, 32, 1598-1605.
[20] Versteeg, H. and Malalasekera, W. (2007) An Introduction to Computational Fluid Dynamics: The Finite Volume Method. Pearson Education Ltd., Harlow.
[21] Schlichting, H. (1935) Boundary Layer Theory. McGraw-Hill, New York.
[22] Sebastian, M. and Egbers, C. (2013) Torque Measurements in a Wide Gap Taylor-Couette Flow. 14th European Turbulence Conference, Lyon, 1-4 September 2013.
[23] Merbold, S., Brauckmann, H. and Egbers, C. (2013) Torque Measurements and Numerical Determination in Differentially Rotating Wide Gap Taylor-Couette Flow. Physical Review E, 87, Article ID: 023014.
[24] van Gils, D., Huisman, S., Bruggert, G.-W., Sun, C. and Lohse, D. (2011) Torque Scaling in Turbulent Taylor-Couette Flow with Co- and Counter-Rotating Cylinders. Physical Review Letters, 106, Article ID: 024502.
[25] Childs, P. and Turner, A. (1994) Heat Transfer on the Surface of a Cylinder Rotating in an Annulus at High Axial and Rotational Reynolds Numbers. 10th International Heat Transfer Conference, Brighton, 13-18.
[26] Grosgeorge, M. (1983) Contribution a letude du refroidissement dune paroi tourante par air charge dhulle pulversdee. Thèses de doctorat, Université de Nacy.
[27] Kostein, L. and Finat’ev, Y. (1963) Investigation of Heat Transfer of a Turbulent Flow of Air in an Annular Gap between Rotating Coaxial Cylinders.
[28] Bouafia, M., Ziouchi, A., Bertin, Y. and Saulnier, J. (1999) étude expérimentale et numérique des transferts de chaleur en espace annulaire sans débit axial et avec cylindre intérieur tournant. International Journal of Thermal Sciences, 38, 547-559.
[29] Nijaguna, B. and Mathiprakasam, B. (1982) Heat Transfer in an Annulus with Spiral Flow. 7th International Heat Transfer Conference, Munich.
[30] Hanagida, T. and Kawasaki, N. (1992) Pressure Drop and Heat Transfer Characteristics of Axial Air Flow through an Annulus with a Deep Slotted Outer Cylinder and a Rotating Inner Cylinder. Heat Transfer Japanese Research, 21, 292-304.
[31] Tachibana, F. and Fukui, S. (1964) Convective Heat Transfer of the Rotational and Axial Flow between Two Concentric Cylinders. Bulletin of JSME, 7, 385-391.
[32] Becker, K.M. and Kaye, J. (1962) The Influence of a Radial Temperature Gradient on the Instability of Fluid Flow in an Annulus with an Inner Rotating Cylinder. Transaction of ASME Journal of Heat Transfer, 82 106-110.
[33] Incropera, F. and De Witt, D. (1985) Introduction to Heat Transfer. Wiley, New York.

Copyright © 2023 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.