Thermal-flow-electric coupling performance analysis of a liquid-immersed battery thermal management system

Ensuring the safety and performance of lithium-ion batteries(LIBs)is a significant challenge for electric vehicles.To tackle this issue,an innovative liquid-immersed battery thermal management system(LIBTMS)using bionic baffles with fish-like perforations is developed.The thermal-flow-electric coupling characteristics of LIBTMSs with different baffle structures(no baffle,conventional baffle,baffle with circular perforations and baffle with fish-like perforations)are systematically investigated using experimental and numerical methods.The results indicate that the forced flow scheme exhibits better thermal management performance and voltage equalization than static flow.Moreover,the LIB temperatures and voltage deviations of different LIBTMSs increase quickly with increasing discharge rates.More importantly,the innovative LIBTMS exhibits the best thermoelectric performance due to its excellent thermoelectric equilibrium behavior caused by high electrical and temperature consistency,as well as the best overall performance involving the balance between the pressure loss and heat transfer capacity of the system.Compared with other structures,the innovative LIBTMS using baffles with fish-like perforations exhibits a maximum reduction of 10.1%,15.2%,25.8%and 9.0%in LIB maximum temperature,maximum temperature difference,system pressure drop and voltage deviation,respectively,under the same operating conditions.Furthermore,for the LIBTMS using baffles with fish-like perforations,the bottom inlet and top outlet configuration and coolant precooling are suggested to enhance cooling performance.

Modelling and Temperature Control of Liquid Cooling Process for Lithium-Ion Battery

Efficient thermal management of lithium-ion battery,working under extremely rapid charging-discharging,is of widespread interest to avoid the battery degradation due to temperature rise,resulting in the enhanced lifespan.Herein,thermal management of lithium-ion battery has been performed via a liquid cooling theoretical model integrated with thermoelectric model of battery packs and single-phase heat transfer.Aiming to alleviate the battery temperature fluctuation by automatically manipulating the flow rate of working fluid,a nominal model-free controller,i.e.,fuzzy logic controller is designed.An optimized on-off controller based on pump speed optimization is introduced to serve as the comparative controller.Thermal control simulations are conducted under regular operating and extreme operating conditions,and two controllers are applied to control battery temperature with proper intervals which is conducive to enhance the battery charge-discharge efficiency.The results indicate that,for any operating condition,the fuzzy logic controller shows excellence in terms of the tracking accuracy of set-point of battery temperature.Thanks to the establishment of fuzzy set and fuzzy behavioral rules,the battery temperature has been throughout maintained near the set point,and the temperature fluctuation amplitude is highly reduced,with better temperature control accuracy of~0.2℃(regular condition)and~0.5℃(extreme condition)compared with~1.1℃(regular condition)and~1.6℃(extreme condition)of optimized on-off controller.While in the case of extreme operating condition,the proposed optimized on-off controller manifests the hysteresis in temperature fluctuation,which is ascribed to the set of dead-band for the feedback temperature.The simulation results cast new light on the utilization and development of model-free temperature controller for the thermal management of lithium-ion battery.