The effect of nano-enhanced phase change material on thermal management system of a lithium-ion battery: A numerical analysis

This study evaluates numerically the effect of nano-enhanced phase change material on thermal management system of a lithium-ion battery for electric vehicles. Numerical investigations were done on an 18650-battery module with a 4 × 4 array filled with PCM28HC as a phase change material (PCM) and nano-enhanced PCM, with 2% and 4% by volume fraction of single-walled carbon nanotubes (SWCNTs) being added to it. The impacts of PCM and nano-enhanced PCM under different discharge rates of 2C, 3C, and 4C were methodically examined on liquid fraction evolution and thermal performance of the battery pack. It was found that increasing the discharge rate from 2C to 4C accelerates the PCM melting with a correspond rise in maximum battery temperature owing to higher heat generation rate. At 2C discharge, the PCM liquid fraction at nearly 1000 s is 0.85, 0.78, and 0.69 for pure PCM, PCM plus 2% SWCNT, and PCM plus 4% SWCNT respectively. The reduction in PCM liquid fractions is 13.43% and 26.86% respectively with PCM plus 2% SWCNT and PCM plus 4% SWCNT when compared to pure PCM implying that PCM plus 4% SWCNT provides better thermal transport and distributes heat more effectively rather than allowing intense localized melting. At 2C discharge, the maximum battery temperature reduced from 310.4 K (pure PCM) to 304.0 K PCM plus 4% SWCNT, while the corresponding reduction is from 315.1 K to 310.4 K at 4C rate. The reduction in maximum temperature with PCM plus 4% SWCNT when compared to pure PCM case is 6.4 K, 3.79 K, and 4.7 K respectively under 2C, 3C, and 4C discharge rates. The heat generation in the battery is reduced by 40.95%, 25.7%, and 16.19% with PCM plus 2% SWCNT under 2C, 3C, and 4C C-rates respectively while with PCM plus 4% SWCNT, the corresponding reductions are 68.28%, 38.43%, and 25.97%.