Heat transfer enhancement of microchannel using nano-encapsulated phase change material for fuel cell thermal management systems

Fuel cells are promising energy conversion devices that offer high efficiency and low emissions. Effective thermal management is essential to maintain fuel cell performance, prevent thermal degradation, and ensure uniform temperature distribution within the cell stack. This study introduced the utilization of non-encapsulated phase change materials (NEPCMs) to improve the heat transfer in a microchannel consisting of an aluminum cast heated from below with integrated tubular hollows for passing the water-NEPCM mixture. Also, this work employed two types of PCM for NEPCM's core and PMMA for NEPCM's shell. Unlike previous works only employing NEPCM, this research focused on the behavior of molten NEPCM within microchannels, considering the influence of the bottom plate temperature of the aluminum cast, Reynolds numbers, and NEPCM volume fractions. Novel insights were provided regarding the development of the NEPCM's boundary layer, its melting characteristics, and the impact of varying parameters. Additionally, the study examined the interplay between NEPCM volume fraction, Reynolds number, and the bottom plate temperature on heat absorption. The results showed that the NEPCM could melt before exiting the microchannel, indicating that the PCMs with suitable melting points were precisely selected. Also, adding NEPCM with the cores of n-octadecane and salt hydrate s27 could improve the heat flux by 4.5 % and 8.21 % in low Reynolds numbers, respectively.