Study of dielectric-based thermal management of second-life battery packs with rectangular vortex generators

The performance of lithium-ion battery (LiB) is influenced by the operational temperature. The thermal management of the battery module depends upon the interaction between coolant and battery surface. The study focuses on analysis of vortex interactions as a commercial dielectric coolant (FC 3283) circulates within battery module. The analysis indicates that the arrangement reduces the maximum average temperature by 26 degrees C in comparison with the conventional methods. However, a maximum temperature difference of 4 degrees C persists at final row of battery cells. Therefore, the vortex generators (V.G.) are deployed to alter the flow behavior to achieve uniform cooling of LiB. Rectangular V.G. alleviates the temperature difference by stretching primary vortices. The V.G.s promote smaller induced vortices, enabling a multiscale distribution of turbulent kinetic energy, reducing the concentration of turbulence near central region of the cell. The induced vortices ensure uniform heat transfer along the cell length. Furthermore, a 15% increase in vorticity magnitude and a 33% rise in an average Nusselt number in the region near the last-row cells is achieved. Overall, employment of V.G.s results in a 2.5 degrees C reduction in maximum cell temperature difference. A novel metric, the operational effectiveness factor (OEF), is coined to assess the combined effect of heat transfer enhancement and additional pumping requirements resulting from the different positions of the V.G. A high OEF value implies the ability of the configuration to maintain a more uniform cell temperature while ensuring lower parasitic power. Middle V.G. configuration achieved highest OEF of 1.35, while bottom V.G. configuration exhibited lowest OEF of 1.11.