# Numerical Study on Heat Transfer Characteristics of Microchannel with Ferrofluid Under Influence of Magnetic Intensity

## TL;DR

This study uses a magnetic fluid in microchannels to improve battery cooling by controlling heat transfer with magnetic fields and electrical insulation.

## Contribution

The paper introduces a novel MHD microchannel cooling system with ferrofluid and evaluates the impact of magnet geometry and insulation on battery thermal management.

## Key findings

- Electrical insulation increases current density by up to 222% and Lorentz force by over 300%.
- A rectangular magnet provides better cooling performance than a cylindrical magnet due to a more uniform magnetic field.
- Under 4C discharge, the insulated rectangular magnet reduces maximum battery temperature by 30% and increases the Nusselt number by 103%.

## Abstract

Effective thermal management is critical for high-power lithium-ion batteries to mitigate excessive heat generation and ensure operational reliability. Failure to maintain a uniform temperature distribution can lead to accelerated capacity fading and severe safety risks, such as thermal runaway. In this study, a ferrofluid-based magnetohydrodynamic (MHD) microchannel cooling system was numerically investigated to elucidate the influence of magnetic intensity, magnet geometry, and electrical boundary conditions on flow behavior and heat transfer performance for battery cooling applications. A fully coupled multiphysics model incorporating electromagnetic, fluid flow, and heat transfer phenomena was developed and validated against experimental and numerical data from the literature. The results show that increasing the applied voltage enhances current density and Lorentz force almost linearly, leading to significant flow acceleration and improved convective heat transfer. Electrical insulation effectively suppresses current leakage into the channel walls, increasing the average current density by up to 222% and the Lorentz force by more than 300%. Compared with a cylindrical magnet, a rectangular magnet provides a more uniform magnetic field distribution and stronger near-wall Lorentz forcing, resulting in superior cooling performance. Under a 4C discharge condition, the insulated rectangular magnet reduces the maximum battery temperature by approximately 30% and increases the average Nusselt number by up to 103% relative to the non-insulated case. The findings reveal the critical roles of magnetic-field-controlled flow symmetry and near-wall forcing in MHD-driven microchannels, and provide practical design guidelines for battery cooling systems with no moving mechanical parts and active electromagnetic flow control.