Thermal Performance of a PCM Reservoir with Y-Shaped Fins for Lithium-Ion Battery Thermal Management

This work numerically investigates how Y-shaped metallic fins embedded in a phase change material (PCM) reservoir affect the thermal management of lithium-ion batteries. The constructal design method was applied to evaluate the effects of the number of fins and Y-shaped bifurcation length (L1) on the maximum battery temperature, temperature difference within the battery cell, and PCM utilization. The fin area was fixed at 10% of the PCM reservoir area, while the number of fins varied from 9 to 18 and L1 from 1.0 to 2.0 mm. For a 5C discharge, the PCM reservoir without fins resulted in a maximum battery temperature of 51.9 °C and a liquid fraction of about 63%. Adding Y-shaped fins reduced the maximum temperature to about 43 °C and increased the liquid fraction to over 96%. The temperature difference within the battery cell was also reduced by up to 43% compared with the finless case. The number of fins had a stronger influence than the bifurcation length, with limited thermal improvements above 12 fins. Comparing 9 fins with L1 = 1.0 mm and 18 fins with L1 = 2.0 mm, the maximum temperature decreased by 1.53 °C. Adding fins also restricted the upward movement of melted PCM driven by natural convection, promoting a more uniform temperature distribution and a lower temperature at the battery/PCM interface.