Flow Optimization for the Thermal Management of Heavy-Duty Batteries Using Viscoelastic Coolants

An efficient thermal management system is crucial for the best performance of heavy-duty electric vehicle (EV) battery packs. The requirement of high heat removal necessitates the use of liquid coolants leading to higher heat transfer coefficient as compared to the conventional air-cooled systems. However, higher viscosity of the liquid coolants increases the pumping power and reduces mixing in the thermal boundary layer (TBL), hence reducing the coefficient of performance (COP, ratio of the heat transfer rate to the pumping power) of the cooling system. We demonstrate a novel immersion cooling strategy, which uses shear-thinning viscoelastic fluids with millimetric structures on the heat transfer surface. The shear-thinning property reduces the pumping power, while the viscoelastic properties generate elastic instabilities on carefully designed surface structures and thereby promote mixing in the TBL. We optimize the shape of the surface structures and properties of the cooling liquids to achieve maximum COP using computational fluid dynamics (CFD) simulation in OpenFOAM. The viscoelastic model liquids are made of solvents and polymers with known relaxation times. We explore the parameter range including solvent and polymer viscosities, relaxation time of the polymers and shape of the surface structures, which provide the initial design guidelines for an experimental setup. Our method is expected to enhance the performance of heavy-duty battery thermal management systems as compared to that of the state-of-the-art solutions.