Experimental Study On Liquid Cooling Heat Dissipation Performance Of Lithium-ion Battery Based On Nanofluids

The search for efficient heat transfer working medium is one of the research directions to improve the performance of battery liquid cooling thermal management.Nanofluid has good heat transfer and fluid properties and is expected to lead to more efficient thermal solutions for battery thermal management systems.In this paper,γ-Al2O3 nanofluid is used as a research object to investigate the application of nanofluid as a heat transfer agent in the liquid-cooled heat dissipation system of lithium-ion batteries by conducting an experimental study on the performance of nanofluid-based liquid-cooled heat dissipation of lithium-ion batteries.The research can be of pioneering and guiding significance for the engineering application of nanofluids in battery thermal management systems.Firstly,the nanofluid preparation method and stability were analysed,a twostep method was established to prepare the nanofluid required for the experiments,and the stability analysis experiments of the prepared nanofluid were carried out using the sedimentation observation method.Secondly,the static performance enhancement of the nanofluid relative to the base fluid was investigated by measuring the thermal physical parameters of the nanofluid and the influencing factors were analysed.The results showed that the addition of dispersant resulted in good dispersion of the nanoparticles in the base fluid without affecting the thermal conductivity of the nanofluid.Both 30 min of magnetic stirring and 1 h of ultrasonic dispersion were able to produce stable nanofluids.0.05%-0.25% mass concentration of γ-Al2O3/deionized water nanofluid increased with increasing particle concentration.The higher the temperature,the higher the thermal conductivity of the nanofluid.Also,the temperature effect on the thermal conductivity of γ-Al2O3/deionized water and γ-Al2O3/thermally conductive fluid nanofluid was much stronger than that of γ-Al2O3/dimethyl silicone oil nanofluid.To further investigate the liquid-cooled heat dissipation performance of nanofluids,an experimental system for liquid-cooled heat dissipation of lithiumion batteries was built,and the effects of different nanofluid concentrations,inlet flow rates,battery discharge multiplication rates and times on the cooling performance of batteries were investigated using the γ-Al2O3/thermally conductive fluid nanofluids as the research object.The results show that the heat transfer performance and fluid performance of γ-Al2O3/thermally conductive fluid nanofluids are different from the base fluid,and the liquid cooling performance ofγ-Al2O3/thermally conductive fluid nanofluid is affected by multiple factors such as flow rate,temperature and duration of operation in the liquid cooling heat dissipation system of lithium-ion batteries.The cooling performance of the γ-Al2O3/thermally conductive fluid nanofluid is steadily improved over a long period of time and at low flow rates,and the higher the concentration of nanofluid,the greater the improvement in cooling performance at three mass concentrations of0.1%,1% and 2%.At a flow rate of 0.9L/min for 1C discharge for 60 min,a 2%mass concentration of γ-Al2O3/thermally conductive fluid nanofluid reduced the average temperature of the Li-ion battery module by 0.52°C compared to the pure thermal fluid and improved the cooling performance by 8.16%.Due to the high viscosity of the thermally conductive fluid,the γ-Al2O3 nanoparticles are poorly dispersed and easily agglomerated in the thermally conductive fluid,and at high flow rates the nanoparticles tend to escape from the van der Waals forces and agglomerate.The flow of the liquid and the action of the circulation pump make the agglomerated nanoparticles do not precipitate,but the nanofluid with serious agglomeration has failed and returned to the nature of the base fluid,thus causing the cooling performance of the γ-Al2O3/thermally conductive fluid nanofluid at high flow rate to be reduced,and the cooling performance of the nanofluid at high concentration is lower than that of the base fluid.The cooling performance of the nanofluid at short time and high temperature is slightly improved at small flow rates,and the cooling performance is also deteriorated at high flow rates,and the effect of concentration on the cooling performance is reduced.The cooling performance of the nanofluid is also influenced by the flow rate at long duration and high temperature,which is generally consistent with the pattern at short duration and high temperature.Experimental studies on the performance of nanofluid-based liquid cooling for lithium-ion batteries have shown that γ-Al2O3/thermally conductive fluid nanofluid can improve the cooling performance of battery modules,but is limited by the stability of the nanofluid.The performance improvement of γ-Al2O3/thermally conductive fluid nanofluids will be greatly reduced under the conditions of large flow rate and high multiplication rate,and even lower than the base fluid.The stable improvement of liquid cooling performance of lithium-ion battery modules by thermally conductive fluid nanofluid occurred at 1C discharge for 60 min at 0.9L/min flow rate,and three mass concentrations of thermally conductive fluid nanofluids at 0.1%,1% and 2% lowered the battery modules by 0.24°C,0.31°C and0.52°C,and improved the cooling performance by 3.77%,5.02% and 8.16%,respectively.The work is instructive for the practical application of nanofluids on battery thermal management systems.