## THERMAL SCIENCE

International Scientific Journal

### Thermal Science - Online First

online first only
### Flow and heat transfer characteristics of high-pressure natural gas in the gaps of high-speed motors with a high radius ratio

**ABSTRACT**

A motor stator-gap-rotor model is established based on the numerical heat transfer theory by using the finite volume method. The flow evolution of high-pressure natural gas in the gap with a radius ratio of 0.971 is investigated. The results demonstrate that the flow patterns of high-pressure natural gas in the motor gap can be categorized into turbulent, spiral Taylor-Couette, and turbulent Taylor-Couette flow; the flow ranges are determined based on the Ta/Re2. Then, the flow and heat transfer characteristics of the cooling medium in the gap under different flow regimes as well as the mechanism of locally enhanced heat transfer in the gap by the Taylor-Couette flow are explored. Finally, the mathematical expressions for the Nusselt number of motor gap are determined in terms of the Reynolds number, Taylor number, and Prandtl number by fitting using the Levenberg-Marquardt and global optimization methods. Using these expressions, the flow and heat transfer characteristics in the motor gap can be predicted. Overall, this study provides useful and novel insights on the design of cooling systems for high-speed motors.

**KEYWORDS**

PAPER SUBMITTED: 2023-11-27

PAPER REVISED: 2024-01-28

PAPER ACCEPTED: 2024-01-31

PUBLISHED ONLINE: 2024-04-14

- Li, S. L., et al., High Speed Electrical Machines: High Speed Electric Machines: Challenges and Design Considerations, IEEE Transactions on Industrial Electronics, 2 (2016), 1, pp. 2 13
- Oguz, A. H., et al., Design and Optimization of an Axially Slitted High Speed Solid Rotor Induction Motor, 2015 9th International Conference on Electrical and Electronics Engineering (ELECO), Bursa, Turkey, 2015, pp. 568 573
- Gao, Q. X., et al., Copper Loss Analysis and Loss Separation Method in a Dynamic Process of Ultra High Speed Motor with Slotless Stator, IET Electric Power Applications, 17 (2023), 4, pp. 464 473
- Li, X. L., et al., Incorporating Harmonic Analysis Based Loss Minimization into MPTC for Efficiency Improvement of FCFMPM Motor, IEEE Transactions on Industrial Electronics, 70 (2023), 7, pp. 6540 6550
- Saari J. Thermal Analysis of High Speed Induction Machines. Finland: Helsinki University of Technology, 1998
- Naseem, U., et al., Experimental Investigation of Flow Instabilities in a Wide Gap Turbulent Rotating Taylor Couette Flow, Case Studies in Thermal Engineering, 14 (2019), 100449, pp. 1 12
- Tanaka, R., et al., DNS of Taylor Couette Flow between Counter Rotating Cylinders at Small Radius Ratio, International Journal of Advances in Engineering Sciences and Applied Mathematics, 10 (2018), 6, pp. 159 170
- Sznitko, E. T., et al., Flow Dynamics in the Short Asymmetric Taylor Couette Cavities at Low Reynolds Numbers, International Journal of Heat and Fluid Flow, 86 (2020), 12, pp. 1 22
- Kusumastuti, A., et al., Characterisation Study of Taylor Couette Flow in Fluid Mixture of used Cooking Oil and Water, Journal of Advance Research in Fluid Mechanics and Thermal Sciences, 80 (2021), 2, pp. 106 114
- Fujii, T., et al., Frequency Analysis of Chaotic Flow in Transition to Turbulence in Taylor Couette System with Small Aspect Ratio, Journal of Physics: Conference Series, Volume 801, International Conference on Computing and Applied Informatics 2016 14 15 December 2016, Medan, Indonesia, 80 1(2016), 2, pp. 106 114
- Swann, P. B., et al., Taylor Couette Poiseuille Flow Heat Transfer in a High Taylor Number Test Rig, Journal of the Global Power and Propulsion Society, 5 (2022), pp. 126 147
- Qin, K., et al., Numerical Investigation on Heat Transfer Characteristics of Taylor Couette Flows Operating with CO2, Applied Thermal Engineering, 165 (2020), 25, pp. 287 298
- Zhang, J., et al., Design and Thermal Performance Analysis of a New Water Cooled Structure for Permanent Magnet Synchronous Motors for Electric Vehicles, Thermal Science, 27 (2023), 3B, pp. 2423 2432
- Xu, Z. Y., et al., Global Fluid Flow and Heat Transfer Characteristics Analysis of an Open Air Cooled Drive Motor for Drilling Application, Case Studies in Thermal Engineering, 37 (2022), 102254
- Dong, H. H., et al., Performance of Air/Spray Cooling System for Large Capacity and High Power Density, Applied Thermal Engineering, 192 (2021), 116925
- Smirnov, P. E., Menter, F. R., Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart Shur Correction Term, Journal of Turbomachinery, 131 (2009), 4, pp. 041010
- Tachibana, F., et al., Convective Heat Transfer of the Rotational and Axial Flow between Two Concentric Cylinders, Bulletin of JSME, 7 (1964), 26, pp. 385-391