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Research Papers: Heat Transfer Enhancement

Numerical Study of Convective Heat Transfer Enhancement in a Pipe Rotating Around a Parallel Axis

[+] Author and Article Information
Aurélie Fasquelle

Jeumont Electric,
Jeumont 59460, France
e-mail: aurelie.fasquelle@jeumontelectric.com

Julien Pellé

Université de Lille Nord de France,
F-59000 Lille;
UVHC, TEMPO/DF2T,
Valenciennes 59313, France
e-mail: julien.pelle@univ-valenciennes.fr

Souad Harmand

Université de Lille Nord de France,
F-59000 Lille;
UVHC, TEMPO/DF2T,
Valenciennes 59313, France
e-mail: souad.harmand@univ-valenciennes.fr

Igor V. Shevchuk

MBtech Group GmbH & Co. KGaA,
Fellbach-Schmiden 70736, Germany
e-mail: ivshevch@i.com.ua

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 13, 2012; final manuscript received September 23, 2013; published online February 26, 2014. Assoc. Editor: Wei Tong.

J. Heat Transfer 136(5), 051901 (Feb 26, 2014) (14 pages) Paper No: HT-12-1501; doi: 10.1115/1.4025642 History: Received September 13, 2012; Revised September 23, 2013

Cooling of electrical machines is nowadays of high interest in order to improve their efficiency. In railway applications, electrical motors can be shrouded in order to avoid particles to be deposited inside. To ensure a satisfactory cooling, pipes are placed inside the rotor and are thus rotating. Improvements in convective heat transfer inside the rotating pipes were numerically investigated. Model was first validated against experimental data and after that several geometry modifications were tested. Influence of the angle of attack of the fluid at the inlet to the pipe was discussed and it was shown that heat transfer can be significantly increased near the pipe inlet. In addition to that changing a circular pipe with an elliptical pipe was investigated in two ways: fixing the same hydraulic diameter or the same equivalent diameter. It was shown that the cooling efficiency can be significantly increased. The best overall heat transfer enhancement of about 45% exhibited elliptic pipes located orthogonal to the rotation radius and having the same cross-section as the reference circular pipes. Results can be used by designers of electrical machines in order to choose the best cooling strategy.

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References

Figures

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Fig. 1

Studied electrical motor, (a) side view, (b) front view, (c) schematic representation of the problem, and (d) mesh at the inlet surface

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Fig. 2

Mean Nusselt numbers vs. the Rossby number, present simulations using the standard k – ω model (points) and Baudoin's empirical equations (7) and (8) (line)

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Fig. 3

Definition of the angle of attack, (a) negative angles, and (b) positive angles

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Fig. 6

Influence of the angle of attack on the local surface heat transfer

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Fig. 5

Flow at the outlet of the rotating circular pipe with β = 0 deg (reference case), (a) quasi-stabilized swirling flow, and (b) temperature distribution

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Fig. 7

Schematics of the circular and both elliptic cross sections (a), path lines at the pipe outlet of elliptic pipes with the fixed hydraulic diameter for the circumferential pipe (b), and radial pipe (c)

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Fig. 4

Effect of the angle of attack, (a) local Nusselt numbers, (b) turbulence intensity, and (c) relative difference with the reference case

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Fig. 8

Comparisons between the two ellipses and the reference case of the circular pipe, fixing the hydraulic diameter, (a) local Nusselt numbers, (b) turbulence intensity, and (c) relative difference from the reference case

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Fig. 9

Temperature distributions at the pipe outlet of elliptic pipes with the fixed hydraulic diameter, (a) circumferential pipe, and (b) radial pipe

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Fig. 10

Comparisons between the two ellipses and the reference case of the circular pipe, fixing the equivalent diameter, (a) local Nusselt numbers, (b) turbulence intensity, and (c) relative difference with the reference case

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Fig. 11

Path lines at the pipe outlet of elliptic pipes with the fixed equivalent diameter, (a) circumferential pipe, and (b) radial pipe

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Fig. 12

Temperature distributions at the pipe outlet of elliptic pipes with the fixed equivalent diameter, (a) circumferential pipe, and (b) radial pipe

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