34 January/February 2024 | E-Mobility Engineering Phase change materials offer intriguing possibilities in the thermal management of EV powertrains as Nick Flaherty explains Chemical brothers Phase-change materials (PCMs) are known for their superior latent heat capacity, acting as heat absorbers without notable temperature increases. This property can be used in many different ways throughout the powertrain of e-mobility systems, from enhancing the heat transfer in the power electronics to cooling the entire battery pack. Unlike Peltier heat pumps, fanbased air cooled plates or liquid cooling systems, PCMs provide passive thermal protection without an additional power supply. They can release trapped heat into their surroundings when no heat is transferred internally, making them reversible heat absorbers. PCMs are also considered superior for maintaining thermal uniformity between battery cells. However, organic materials with relatively poor thermal conductivity make up the majority of PCMs within the optimum temperature range for Li-ion batteries, which therefore limits their effectiveness. Despite this, phase change materials paraffin and fatty acids are often used due to their relatively constant thermal and chemical characteristics, resilience to corrosives, and they are more affordable than other inorganic materials. Both are currently considered promising materials for battery thermal management applications because of these characteristics as they melt and carry heat away more effectively. Researchers have added other materials into the paraffin base such as graphite and graphene, metal compounds and nanoparticles to improve thermal conductivity. However, there are still several other limitations, such as weight and environmental side effects, while metal additives in particular require additional protection against corrosion and abrasion. Other PCMs use refrigerant materials that turn from a liquid to a gas to provide cooling for battery packs. Dual phase liquid cooling for battery packs (Image courtesy of Carrar)
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