# Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

^{2}K). The axial water flow had a higher water velocity and a larger heat-transfer coefficient (1886.4 W/m

^{2}K). The higher water velocity resulted in better cooling performance. Rehman et al. [16] compared various coolant jackets with different numbers of flow passes. Considering the pump performance, a cooling jacket with six passes at a flow rate of 10 LPM had the best cooling performance. The maximum temperature was approximately 100 °C. For an electric-vehicle motor, a large amount of heat is generated at the coil. The water-cooling method is not appropriate for removing heat from the coil. This method has a low heat-transfer rate in the radial direction, because the motor is cooled indirectly through the housing. Direct cooling is more effective for removing the heat inside the motor [17].

## 2. Materials and Methods

#### 2.1. Motor Description

#### 2.2. Numerical Analysis

^{®}was used for the analysis. The continuum equation (mass conservation law) and Navier–Stokes equations (momentum conservation law) were used as the fundamental governing equations of the MPS method:

^{2}u + g + ∇ϕ

^{−13}T

^{6}− 4 × 10

^{−10}T

^{5}+ 4 × 10

^{−7}T

^{4}− 0.0002T

^{3}+ 0.54T

^{2}− 8.2514T + 522.74

#### 2.3. Experimental Setup

## 3. Results and Discussion

#### 3.1. Effect of Spray Nozzle on Flow Field

_{oilfilm}is given as follows:

_{oilfilm}= A

_{oil}/A

_{coil}

_{coil}represents the total surface area of the coil, and A

_{oil}represents the contact area between the coil and the oil.

#### 3.2. Effect of Inlet Diameter and Number of Inlets on Flow Field

#### 3.3. The Effects of Oil Flow Rate on Flow Field

#### 3.4. Effect of Oil Temperature on Flow Field

#### 3.5. Studied Oil Injection Method

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 4.**Cross section of coil: (

**a**) dripping nozzle; (

**b**) full cone nozzle (spray angle: 45°); (

**c**) full cone nozzle (spray angle: 60°).

**Figure 5.**Oil film for different spray-nozzle types: (

**a**) oil film formation rate; (

**b**) oil film thickness.

**Figure 7.**Oil flow according to the number and diameter of inlets: (

**a**) 3.175 mm and 8 inlets; (

**b**) 6.35 mm and 6 inlets; (

**c**) 9.525 mm and 4 inlets.

**Figure 11.**Oil flow according to the temperature at 6 LPM: (

**a**) 20 °C; (

**b**) 40 °C; (

**c**) 60 °C; (

**d**) 80 °C.

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**MDPI and ACS Style**

Ha, T.; Kim, D.K. Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding. *Energies* **2021**, *14*, 747.
https://doi.org/10.3390/en14030747

**AMA Style**

Ha T, Kim DK. Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding. *Energies*. 2021; 14(3):747.
https://doi.org/10.3390/en14030747

**Chicago/Turabian Style**

Ha, Taewook, and Dong Kyu Kim. 2021. "Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding" *Energies* 14, no. 3: 747.
https://doi.org/10.3390/en14030747