# NOVEL APPROACH TO ANALYTICAL MODELLING OF STEADY-STATE HEAT TRANSFER FROM THE EXTERIOR OF TEFC INDUCTION MOTORS

## Main Article Content

## Abstract

The purpose of this paper is to propose a novel approach to analytical modelling of steady-state heat transfer from the exterior of totally enclosed fan- cooled (TEFC) induction motors. The proposed approach is based on the geometry simplification methods, energy balance equation, modified correlations for forced convection, the Stefan-Boltzmann law, air-flow velocity profiles and turbulence factor models. To apply modified correlations for forced convection, the motor exterior is presented with surfaces of elementary 3D shapes as well as the air-flow velocity profiles and turbulence factor models are introduced. The existing correlations for forced convection from a short horizontal cylinder and correlations for heat transfer from straight fins (as well as inter-fin surfaces) in axial air-flows are modified by introducing the Prandtl number to the appropriate power. The correlations for forced convection from straight fins and inter-fin surfaces are derived from the existing ones for combined heat transfer (due to forced convection and radiation) by using the forced-convection correlations for a single flat plate. Employing the proposed analytical approach, satisfactory agreement is obtained with experimental data from other studies.

## Article Details

**Thermal Science**, [S.l.], mar. 2017. ISSN 2334-7163. Available at: <http://thermal-science.tech/journal/index.php/thsci/article/view/2179>. Date accessed: 23 june 2017. doi: https://doi.org/10.2298/TSCI150629091K.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Authors retain copyright of the published article and have the right to use the article in the ways permitted to third parties under the - Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) licence. Full bibliographic information (authors, article title, journal title, volume, issue, pages) about the original publication must be provided and a link must be made to the article's DOI.

The authors and third parties who wish use the article in a way not covered by the the -Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) licence must obtain a written consent of the publisher. This license allows others to download the paper and share it with others as long as they credit the journal, but they cannot change it in any way or use it commercially.

Authors grant to the publisher the right to publish the article, to be cited as its original publisher in case of reuse, and to distribute it in all forms and media.

Accepted 2017-03-13

Published 2017-03-13

## References

[2] Romo, J. L., Adrián, M. B., Prediction of internal temperature in three-phase induction motors with electronic speed control, Electric Power Systems Research 45 (1998), 2, pp. 91-99.

[3] Huai, Y., Melnik, R. V. N., Thogersen, P. B., Computational analysis of temperature rise phenomena in electric induction motors, Applied Thermal Engineering 23 (2003), 7, pp. 779-795.

[4] Ghai, M. L., Jakob, M., Local coefficients of heat transfer for straight fins, American Society of Mechanical Engineers Paper No. 50-S-18 (1950), pp. 1-22.

[5] Ghai, M. L., Heat transfer in straight fins, in: General Discussion on Heat Transfer, American Society of Mechanical Engineers, USA, 1951, pp. 180-182.

[6] Valenzuela, M. A., Tapia, J. A., Heat transfer and thermal design of finned frames for TEFC variable speed motors, in: IEEE Proceedings of 32nd Annual Conference on IEEE Industrial Electronics – IECON 2006, Paris, France, 2006, pp. 4835-4840.

[7] Valenzuela, M. A., Tapia, J. A., Heat transfer and thermal design of finned frames for TEFC variable-speed motors, IEEE Transactions on Industrial Electronics 55 (2008), 10, pp. 3500-3508.

[8] Fuchs, E. F., Masoum, M. A. S., Power Quality in Power Systems and Electrical Machines, second ed., Elsevier Academic Press, USA, 2008, pp. 252.

[9] Klimenta, D. O., Hannukainen, A., An approximate estimation of velocity profiles and turbulence factor models for air-flows along the exterior of TEFC induction motors, Thermal Science, Published online: May 8, 2016, DOI: 10.2298/TSCI150626090K.

[10] Xypteras, J., Hatziathanassiou, V., Thermal analysis of an electrical machine taking into account the iron losses and the deep-bar effect, IEEE Transactions on Energy Conversion 14 (1999), 4, pp. 996- 1003.

[11] Chen, Y.-C., Chen, B.-C., Chen, C.-L., Dong, J. Q., CFD thermal analysis and optimization of motor cooling fin design, in: Proceedings of 2005 ASME Summer Heat Transfer Conference – HT2005, San Francisco, California, USA, 2005, paper ID HT2005-72567, pp. 1-5.

[12] Hewitt, G. F., Hall-Taylor, N. S., Annular Two-Phase Flow, Pergamon Press, Oxford, GB, 1970.

[13] Balachandran, P., Engineering Fluid Mechanics, PHI Learning Private Limited, New Delhi, India, 2011, pp. 232-275.

[14] Webster, J. G., Eren, H., Measurement, Instrumentation, and Sensors Handbook: Spatial, Mechanical, Thermal, and Radiation Measurement, second ed., CRC Press, Taylor & Francis Group, LLC, Boca Raton, USA, 2014, pp. 57.6-57.8.

[15] Holland, F. A., Bragg, R., Fluid Flow for Chemical Engineers, second ed., Butterworth-Heinemann, Oxford, GB, 1995, pp. 85-88.

[16] Kovalev, E. B., Burkovskii, A. N., Tokarenko, A. T., Heat release in channels between frame-ribbing of enclosed asynchronous motors, Elektrotekhnika 36 (1965), 11, pp. 27-29.

[17] Chapman, S. J., Electric Machinery Fundamentals, fifth international ed., McGraw-Hill, Inc., 2011, pp. 307-403.

[18] Mills, A. F., Heat Transfer, Richard D. Irwin, INC., Homewood, IL, USA, 1992, pp. 330-333.

[19] Cobb, E. C., Saunders, O. A., Heat transfer from a rotating disk, Proceedings of the Royal Society of London, Series A , Mathematical and Physical Sciences 236 (1956), 1206, pp. 343-351.

[20] Axcell, B. P., Thianpong, C., Convection to rotating disks with rough surfaces in the presence of an axial flow, Experimental Thermal and Fluid Science 25 (2001), 1-2, pp. 3-11.

[21] Wiberg, R., Lior, N., Heat transfer from a cylinder in axial turbulent flows, International Journal of Heat and Mass Transfer 48 (2005), 8, pp. 1505-1517.

[22] Kobus, C. J., Shumway, G., An experimental investigation into impinging forced convection heat transfer from stationary isothermal circular disks, International Journal of Heat and Mass Transfer 49 (2006), 1-2, pp. 411-414.

[23] Kobus, C. J., Wedekind, G. L., An experimental investigation into forced, natural and combined forced and natural convective heat transfer from stationary isothermal circular disks, International Journal of Heat and Mass Transfer 38 (1995), 18, pp. 3329-3339.

[24] ASHRAE, Chapter 4 – Heat transfer, in: 2009 ASHRAE Handbook – Fundamentals, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, USA, 2009, pp. 4.1- 4.34.

[25] Kylander, G., Thermal modelling of small cage induction motors, Ph.D. thesis, School of Electrical and Computer Engineering, Chalmers University of Technology, Göteborg, Sweden, 1995.