<p>To guarantee the safety and prolong the lifetime of lithium-ion (Li-ion) power batteries within electric vehicles, a thermal management system is essential. In this study, a three-dimensional analysis of an 8s1p (8 series and 1 parallel batteries in a stage) battery module consisting of 8 prismatic Li-ion batteries is performed using a multi-domain modeling framework. The well-known Newman, Tiedemann, Gu, and Kim (NTGK) model is used for subscale electrochemical modelling, and the problem of heat generation due to electrical resistance, electrochemical reactions, and the temperature in the battery cell domain is solved. A new method of thermal management system based on liquid cooling via a cold plate utilizing glycol aqueous solution (GAS) is proposed. The properties of GAS are calculated by the piecewise-linear interpolation of the temperature. Cooling simulations of the battery module are carried out at different GAS volume concentrations and flow velocities. The temperature evolutions at different volume concentrations of ethylene glycol (EG) and the inlet flow velocities are determined, and the results are found to be in good agreement with the experiments. Strategies for modifying the properties of GAS to release the heat generated by the battery module are proposed. It is found that, without cooling, the temperature of the battery module increases quickly to 80 °C, which could trigger thermal runaway. However, the cell temperature and temperature gradients were maintained at a tolerable level at a suitable inlet flow velocity and volume concentration of GAS, even at a 5C discharge rate. The simulation and experimental results demonstrate that the temperature difference between the 8 battery cells reaches the minimum when the volume concentration of EG is 70%, which means that the optimum cooling uniformity of the battery module can be reached at this volume concentration. For 70% GAS, the large temperature difference between the cold plate and GAS dominates the heat transfer at the inlet in spite of the thicker boundary layer (the high Prandtl number); in other parts, although the temperature difference decreases, the Nusselt number is large and convective heat transfer is enhanced. For a large-scale battery module, the heat generated by the Li-ion cells accumulates inside the module, which poses a high risk of thermal runaway. The GAS flows into the center of the battery module through channels, and the predicted maximum cell temperature and maximum temperature difference in the module are found to be maintained below 40 °C and 5 °C, respectively, at a 5C discharge rate.</p>

Effects of the Properties of Glycol Aqueous Solution on Battery Cooling Performance Based on Cold Plates

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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