Thermal modelling and numerical simulation of nanofluid-based battery thermal management system using Lattice Boltzmann method under high discharge rate

Effective battery thermal management systems (BTMS) are essential to ensure performance, safety, and lifetime of lithium-ion battery packs in electric vehicles, especially under high charge/discharge conditions. In this regard, this study investigates a nanofluid-based cooling system for a battery module operating under 5C discharge rate. Batteries in a module are placed in a wavy cooling channel, and the proposed design is analysed for different parameters, including coolant mass flow rate (0.002 to 0.05 kg/s), nanoparticle volume fraction (0 to 0.04), battery spacing (0 to 5 mm) and channel width (4, 5 and 6 mm). For the numerical simulation, a two-dimensional conjugate lattice Boltzmann framework is developed, integrating a two-relaxation time scheme for the flow field with a single relaxation time for the thermal field. The simulation results indicate that increasing the coolant mass flow rate significantly reduces the maximum cell temperature, but the benefit saturates once the flow rate exceeds about 0.02 kg/s. It is revealed that adding Al₂O₃ nanoparticles with a volume fraction of 0.02 causes 1.5 K decrease in the maximum temperature of the batteries compared to pure water. With 2 mm battery spacing and 5 mm channel width, the module operates within an approximately 300–305 K temperature band during 5C discharge. The methodology proposed in this study can be further implemented to investigate various designs of battery thermal management systems.