Lithium (Li)-ion battery thermal management systems play an important role in electric vehicles because the performance and lifespan of the batteries are affected by the battery temperature. This study proposes a framework to establish equivalent circuit models (ECMs) that can reproduce the multi-physics phenomenon of Li-ion battery packs, which includes liquid cooling systems with a unified method. We also demonstrate its utility by establishing an ECM of the thermal management systems of the actual battery packs. Experiments simulating the liquid cooling of a battery pack are performed, and a three-dimensional (3D) model is established. The 3D model reproduces the heat generated by the battery and the heat transfer to the coolant. The results of the 3D model agree well with the experimental data. Further, the relationship between the flow rate and pressure drop or between the flow rate and heat transfer coefficients is predicted with the 3D model, and the data are used for the ECM, which is established using MATLAB Simulink. This investigation confirmed that the ECM’s accuracy is as high as the 3D model even though its computational costs are 96% lower than the 3D model.

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Sound measurements were carried out using rocket-based propagation diagnostics in the middle and upper atmosphere via infrasonic/acoustic waves to investigate their frequency dependence. The S-310-41 sounding rocket was used, equipped with one main microphone, two sub-microphones, and a loudspeaker, to examine the sound propagation in the payload section of the rocket as a function of the ambient atmospheric pressure. The output from the loudspeaker showed a clear trend of gradual attenuation with decreasing atmospheric pressure at almost all frequencies. Acoustic wave propagation was measured, and was in good agreement with the predictions of attenuation of the sound strength of the mass spectrometer incoherent scatter model (NRLMSISE-00).

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