Investigation of Hybrid Battery Thermal Management Systems incorporating Internal-External Fins and Phase Change Materials

Abstract

The thermal management of lithium-ion batteries is critical for ensuring their safety, longevity, and performance, especially to prevent thermal runaway during high-temperature conditions and continuous cycling. This study introduces a hybrid phase change material (PCM)-liquid battery thermal management system (BTMS), which integrates cylindrical and longitudinal internal-external fins into PCM-based BTMSs. These innovative fin designs for cylindrical lithium-ion batteries simultaneously enhanced conduction and convection heat transfer within PCM while addressing temperature uniformity around the circular perimeter and along the height of batteries. The hybrid BTMS combined PCM latent heat utilisation with liquid cooling to improve energy efficiency, recover PCM latent heat, and enhance natural convection through a metal casing and strategically designed fins.
The fin-enhanced PCM-based BTMS effectively maintained battery surface temperatures below the optimal threshold of 318.15 K for safety and lifespan, even under high current rates and elevated ambient temperatures. Additionally, the PCM-based BTMS with 1 cylindrical and 4 longitudinal internal-external fins provided the highest fin efficiency compared to the PCM-based BTMSs with higher fin quantities and extended the total PCM melting period by up to 37.76% while reducing the total PCM solidification period by up to 37.56% compared to the PCM-based BTMS without fins. This maintained battery temperatures within the optimal range for a longer period and enhanced BTMS recovery.
The role of convection during PCM melting was highlighted, with a generalisation of PCM liquid fraction and Nusselt number in terms of Fourier number, modified Stefan number, Rayleigh number, and fin quantity. Sensitivity analyses identified optimal PCM thickness, fin size, and material selection. Statistical analysis revealed that ambient temperature and liquid coolant temperature were the most influential factors on the maximum battery surface temperature in the hybrid PCM-liquid BTMS, whereas PCM material and PCM thickness had the least impact.
The proposed BTMS designs, with their ease of manufacturing, can reduce maintenance costs by providing temperature uniformity within the module, benefiting sectors such as automotive, light and compact electronics, and renewable energy. This study provides a strong foundation for further exploration of BTMS designs, emphasising the need for balanced designs to achieve efficient thermal management without compromising energy density or excessively increasing power consumption. Future work should focus on investigating the performance of these BTMSs through experimental testing under real-world conditions to advance their adoption in energy storage technologies.

Date of Award	16 Jan 2025
Original language	English
Awarding Institution	Birmingham City University
Supervisor	Noel Perera (Director of Studies) & Jens Lahr (Second Supervisor 1)