Effective cooling and thermal management strategies for cylindrical lithium-ion battery pack system leveraging supercritical CO2

This study presents a novel supercritical CO2 based thermal management system for cylindrical lithium-ion battery packs, leveraging 3D finite volume simulations with fully coupled multiphysics to optimize cooling performance. Unlike conventional air or liquid cooling, the proposed system exploits sCO2's thermophysical advantages near its critical point (8 MPa, 34.8 degrees C), where peak heat transfer coefficients minimize temperature differentials between the fluid and battery surfaces. Key parameters such as spacing between batteries in the streamwise and spanwise directions, battery discharge rate, operating pressure, and sCO2 temperature are analyzed to comprehensively assess system efficacy. Results demonstrate a consistent and significant reduction in maximum battery pack temperature across all discharge rates compared to scenarios without thermal management. For example, at a 1C discharge rate, the maximum temperature decreases by 16.91 degrees C, with further reductions observed at higher discharge rates, reaching 39.88 degrees C and 66.12 degrees C at discharge rates of 2C and 3C, respectively. Parametric analysis reveals that optimal battery spacing (0.25-0.275 x hydraulic diameter) and operating conditions (e.g., 8 MPa pressure, Re = 30,000-40,000) reduce peak temperatures by 16.9-66.1 degrees C across 1C-3C discharge rates, outperforming passive thermal management. Notably, sCO2 achieves significantly lower pumping power than water cooling at comparable Re, despite a trade-off in absolute cooling capacity. The work advances prior literature by demonstrating how sCO2's near-critical behavior mitigates thermal gradients while maintaining energy efficiency-a critical advantage for high-density electric vehicle battery packs. Challenges such as pressure drop sensitivity at 8 MPa versus 10 MPa are quantified, providing actionable insights for system design.