Performance investigation of mono and hybrid nanofluids in a liquid battery thermal management system under high discharge rate and different drive cycle conditions

With the rapid increase in electric vehicles (EVs) power demand, newer and more efficient thermal management systems are required to maintain the EV battery temperature within the optimum range between 20 and 40 °C to ensure a safe and efficient operation. To address these requirements, this study investigated the overall performance of a nanofluid liquid BTMS for two cylindrical lithium-ion battery modules with 12 and 100 battery cells each. The analysis was conducted using a 3C discharge rate as well as steady and variable discharge rates for WLTC3 and NEDC drive cycles. Three nanoparticle types (SWCNT, Fe₃O₄ TiO₂, and Cu TiO₂) were investigated under three different volumetric concentrations (1 %, 2 %, 3 %) and compared to the base fluid (water), the assessment considered four different Reynolds number values, and the evaluation was based on the maximum temperature and temperature difference, pressure drop, Nusselt number, in addition to a performance factor which takes into account the nanofluid heat transfer enhancement and the pressure drop increase. Based on the performance evaluation, the BTMS performance is found to be directly proportional to the flow Reynolds number and the optimum nanofluid is found to be SWCNT water nanofluid with 3 % concentration, compared to water, it achieved a 3.56 % and 13.81 % reduction in maximum temperature and temperature difference respectively, yielding a performance factor of 1.58. Furthermore, considering the two investigated drive cycle conditions, the SWCNT water nanofluid lowered the maximum temperature and temperature difference by 0.5 % and 3.3 % respectively leading to an 80.13 % enhancement in Nusselt number compared to water, proving the effectiveness of using the proposed nanofluid BTMS under diverse driving conditions.