Numerical study on the design optimization of cell-to-pack liquid cooling system and thermal management performance

Lithium-ion batteries (LIBs) are the primary power source for new energy vehicles (NEVs). Under typical operating conditions such as startup, acceleration, hill climbing, and high-speed cruising, severe high-rate discharge frequently occurs, leading to substantial internal heat generation within the battery cells. Inadequate or uneven heat dissipation can easily cause localized overheating, which significantly compromises battery safety, dynamic performance, and cycle life. To resolve this thermal hazard for high-power Cell-to-Pack (CTP) battery systems, this work establishes a full-scale CTP pack physical model and couples it with the NTGK multi-scale electrochemical model to perform electrothermal co-simulations under harsh 5C high-rate discharge conditions. Two groups of controlled variables are configured for systematic parametric analysis: four coolant inlet flow velocities (0.1 m/s, 0.5 m/s, 1 m/s, and 2 m/s) are employed to quantify the effect of flow rate on cooling performance, while three novel double-layer flow channel topologies-straight, serpentine, and honeycomb layouts-are constructed to elucidate the influence of channel topology on cooling efficiency. Their performance is subsequently benchmarked comprehensively against conventional liquid cooling configurations. Simulation results indicate that elevating coolant velocity continuously boosts the heat dissipation capacity of all three channel schemes. At the flow rate of 2 m/s (below the industry upper limit of 2.5 m/s), the CTP system exhibits significantly narrowed temperature distribution, superior thermal uniformity, and effective mitigation of hot spots, thereby ensuring reliable system-wide thermal management. Benefiting from turbulent flow intensified by repeated bends, the serpentine channel achieves a superior volume ratio of 0.97 and mass energy density of 177.61 Wh/kg, with a sustainable average flow velocity reaching 1.91 m/s. The honeycomb structure, characterized by multi-point split-flow grid channels, achieves an excellent trade-off between structural compactness (volume ratio = 0.965) and heat exchange efficacy, improving cooling efficiency by 26.83% while maintaining a minimum peak module temperature of just 41.34 °C. All three proposed channel configurations meet the thermal management requirements for high-rate discharging battery packs and demonstrate comprehensive performance advantages over conventional liquid cooling systems. This work provides both robust theoretical underpinnings and actionable engineering guidance for optimizing the thermal architecture of high-rate CTP lithium-ion battery systems.