*Article* **Numerical Study on the Influence of Vortex Generator Arrangement on Heat Transfer Enhancement of Oil-Cooled Motor**

**Junjie Zhao 1,†, Bin Zhang 1,†, Xiaoli Fu 1,\* and Shenglin Yan 2,\***


**Abstract:** At present, vortex generators have been extensively used in radiators to improve the overall heat transfer performance. However, there is no research on the effect of vortex generators on the ends of motor coils. Meanwhile, the current research mainly concentrates on the attack angle, shape and size, and lacks a detailed study on the transverse and longitudinal distance and arrangement of vortex generators. In this paper, the improved dimensionless number *R* is used as the key index to evaluate the overall performance of enhanced heat transfer. Firstly, the influence of the attack angle on heat transfer enhancement is discussed through a single pair of rectangular vortex generators, and the results demonstrate that the vortex generator with a 45◦ attack angle is superior. On this basis, we compare the effects of different longitudinal distances (2 *h*, 4 *h*, and 6 *h*, *h* meaning the height of vortex generator) on enhanced heat transfer under four distribution modes: *Flow-Up* (*FU*)*, Flow-Down* (*FU*)*, Flow-Up-Down* (*FUD*)*, Flow-Down-UP* (*FDU*). Thereafter, the performances of different transverse distances (0.25 *h*, 0.5 *h*, and 0.75 *h*) of the vortex generators are numerically simulated. When comparing the longitudinal distances, *FD* with a longitudinal distance of 4 *h* (*FD-*4 *h*) performs well when the Reynolds number is less than 4000, and *FU* with a longitudinal distance of 4 *h* (*FU-*4 *h*) performs better when the Reynolds number is greater than 4000. Similarly, in the comparison of transverse distances, *FD-*4 *h* still performs well when the Reynolds number is less than 4000, and *FU* with a longitudinal distance of 4 *h* and transverse distance of 0.5 *h* (*FU-*4 *h*–0.5 *h*) is more prominent when the Reynolds number is greater than 4000.

**Keywords:** vortex generator; arrangement; heat transfer; numerical simulation
