CFD ANALYSIS OF ZNO NANOFLUID FOR PERFORMANCE ENHANCEMENT OF LI-ION BATTERY THERMAL MANAGEMENT SYSTEMS

Abstract

The LiFePO4 battery packs should be thermally controlled so that the operational safety, the performance stability, and long services in an electric vehicle can be ensured. The problem with cylindrically-shaped 32650 cells is that they become easily overheated and heat is not evenly distributed when the discharge rate is high and can lead to rapid electrochemical degradation and cause thermal runaway. Conventional coolants such as water and ethylene glycol mixture are not conductive to heat well hence restricting heat extraction. To facilitate the correction of this weakness, the present paper investigates the application of ZnO nanofluid as a new state of art coolant to facilitate the performance of a liquid-cooled Battery Thermal Management System (BTMS). ANSYS Fluent in a two-dimensional model is modelled and simulated to represent the steady-state conditions of the discharge of a 32650 LiFePO4 cylindrical cell. Since 70: 30 water-ethylene glycol mixture is used as a base fluid, the ZnO nanoparticles are dispersed with a lesser volume concentration of 1. The equations of governing continuity, momentum and energy are solved by finite volume method. They are systematically studied to determine the concentration of nanoparticles and the velocity of coolants in terms of maximum temperature of the battery, temperature field, the characteristics of heat transfer, and pressure drop with the aim of establishing the thermo-hydraulic performance of the nanofluid-based cooling system. The results of the simulation show that the addition of ZnO nanoparticles will augment the effective thermal conductivity of the base fluid in terms of reduced maximum cell temperature and a high level of uniformity in temperature compared with the traditional coolant. Although slight increase in pressure drop is observed with the concentration of nanoparticles, a concentration of below 1 percent is observed to provide an optimum trade-off between thermal enhancement and pumping power requirements. The findings show that ZnO nanofluid in 70:30 water-ethylene glycol solution can be considered as the solution to improved BTMS design in the electric car battery packs.