Conjugate heat transfer in minichannel with embedded pin fins or porous medium: application to battery cooling system

Fatukasi, Samson

Conjugate heat transfer in minichannel with embedded pin fins or porous medium: application to battery cooling system

Thesis / Dissertation

2026

Publisher

University of Cape Town

Department

Department of Mechanical Engineering

Faculty

Faculty of Engineering and the Built Environment

Abstract

Electric vehicle technology is gaining global attention as a sustainable alternative to fossil fuels, rapidly replacing internal combustion engine vehicles. However, managing the thermal performance of lithium-ion batteries - the optimal energy storage system for electric vehicles remains a significant challenge. This study focuses on developing an effective cooling system to manage the thermal challenges of a cylindrical lithium-ion battery pack operating under a high discharge rate of 6 C, generating volumetric heat transfer of 3340135 W m3⁄ of 20Ahm−2 arranged in parallel and operating at a temperature of 298 K. The thermal performance of the cooling system was analyzed under varying Reynolds numbers by evaluating different configurations of channels mounted on a rectangular frame. The study explored the potential of heat transfer enhancement using circular, elliptical, and rectangular solid pin fins, as well as aluminum foam inserts with varying porosities. The effects of insert location, spacing, and three insert arrangements within the fluid domain were also investigated. Numerical simulations were conducted using ANSYS® Fluent 20R1 to solve the governing equations of heat transfer and fluid dynamics under different flow orientations. Results show that the cooling system achieved the highest heat transfer rate density when three channels were mounted on the rectangular frame, irrespective of the insert configuration. The insert placed closest to the inlet yielded the best thermal performance. Although low- and medium-porosity aluminum foam inserts enhanced heat transfer, their use was discouraged due to the high pumping power requirements. Among the three-insert arrangements, a spacing of 2.0 mm provided optimal thermal performance. Counterflow configurations consistently outperformed parallel flow arrangements. Notably, a single insert positioned at one-eighth of the channel length from the inlet (L/8) 7×108 outperformed systems with three inserts, regardless of spacing arrangements. At the peak performance of the system with a circular, elliptical, and rectangular aluminum foam of 0.9 porosity insert, 46.1%, 36.2%, and 39.40% of improved enhancement factors were achieved respectively, by the cooling system compared with solid pin fin counterparts. Overall, a cooling system with a circular solid pin fin insert positioned at L/8 demonstrated superior performance, exceeding elliptical and rectangular inserts by 10.6% and 4.2%, respectively. The optimization of this system using constructal theory, achieved a thermal performance enhancement of over 390% at a Bejan number of 7 × 108 compared to its unoptimized counterpart. Generally, the findings from this study show that for a battery cooling system, the number of mounted channels, flow orientation, insert's (solid pin fin or aluminum foam) location, and its number in the fluid domain have a significant effect on the dissipation of the heat from the battery pack. The influence of types, shapes, and porosities of the aluminum foam insert on the overall thermal performance enhancement of the cooling system was demonstrated. Overall, this study provides useful knowledge for enhanced design and effective electric vehicle battery pack heat dissipation of the cooling system.