What question did this study set out to answer?

This study aims to analyze the thermal and hydrodynamic behavior of lithium-ion batteries using various dielectric fluids.

June 11, 2026Open Access

Computational Fluid Dynamics Analysis of Battery Immersion Cooling: Impact of Dielectric Fluid Thermophysical Properties

Puntos clave

This study aims to analyze the thermal and hydrodynamic behavior of lithium-ion batteries using various dielectric fluids.
Three-dimensional computational fluid dynamics simulations were conducted using ANSYS Fluent.
Twenty dielectric fluids were evaluated for their thermophysical properties including viscosity and thermal conductivity.
The battery module comprised sixteen lithium-ion cells immersed in the dielectric fluids.
Mineral oil and PAO4 reduced maximum LIB cell temperatures by approximately 4 K compared to the least effective fluids, undecane and cumene.
Temperature uniformity improved by approximately 32.4% for mineral oil, Novec 7000, and PAO4 compared to cumene.
Higher pressure drops were noted for mineral oil and PAO4 due to their higher viscosities, increasing the required pumping power.

Resumen

The rapid growth in the electric vehicle sector has increased demand for advanced battery thermal management systems (BTMSs) with high heat-dissipation capacity and temperature uniformity. Immersion cooling using dielectric fluids has recently been recognized as a promising alternative technology to conventional indirect liquid cooling methods. This study investigates the thermal and hydrodynamic behaviour of a sixteen-lithium-ion cell battery (LIB) module immersed in low-viscosity dielectric fluids using three-dimensional computational fluid dynamics simulations. In this context, a total of twenty dielectric fluids are evaluated using the ANSYS Fluent solver, with particular emphasis on the effects of key thermophysical properties, including viscosity, density, specific heat capacity, and thermal conductivity. The simulation findings reveal that mineral oil and PAO4 yield the lowest maximum LIB cell temperatures, with a reduction of approximately 4 K compared to the least effective dielectric fluids, such as undecane and cumene. Moreover, in terms of temperature uniformity, mineral oil, Novec 7000, and PAO4 exhibit the most homogeneous temperature distributions among the twenty dielectric fluids. In addition, they show an improvement in the temperature uniformity index of approximately 32.4% compared with the least effective dielectric fluid, cumene. On the other hand, mineral oil and PAO4 generate significantly higher pressure drops because of their relatively high viscosities, which increases hydraulic resistance and pumping power requirements. These findings demonstrate that excellent thermal performance does not necessarily correspond to optimal overall thermo-hydraulic behaviour. Overall, the results confirm that immersion-BTMS performance is governed by a complex interaction between dielectric fluid thermophysical properties and flow behaviour, highlighting the importance of coupled thermo-hydraulic optimization in the selection of dielectric fluids for next-generation immersion-cooled battery systems.

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