Advertising feature CFD Simulation Cases CFD Simulation consisted of several models that started with a seven-cell mini-module and progressed up to a full-scale design-intent module as shown in Figure 4. In total, over one hundred CFD simulation cases investigated a wide range of flow rates and ambient temperatures for each module using three cell carriers. The alternative carriers explored the effect on heat transfer when using different manufacturing methods which vary the shape of the fluid channels around the cells. Results - Average Intra-cell temperatures Figure 5 shows the average measured intra-cell temperature delta from the rig test experiments. The deltas were established under steady state simulated slow and ultra-fast charge conditions of 0.5C and 3C respectively at various thermal management fluid flow rates. The test results align with the simulation, the final column highlights the temperature uniformity of the module showing an intra-cell delta at ~1.2 degC when generating heat equivalent to 3C ultra-fast charging and the pump set at maximum flow rate. Module pressure delta & fluid pump power consumption In an EV the power consumed by the thermal fluid pump comes from the vehicle battery pack so any reduction can translate to an increase in vehicle range. The pump power required to push fluid through the battery is related to the pressure delta across to the module or pack. Two Castrol ON EV Thermal Fluids were selected to explore the impact of fluid properties on the system. Fluid 1 had slightly superior thermal properties while Fluid 2 had significantly lower viscosity & slightly higher density As shown in Figure 6 at 79% of maximum flow rate across a range of temperatures Fluid 2 reduced pressure drop across the module by between 70% and 19% compared to Fluid 1. This behaviour aligns with the temperature dependant kinematic viscosity profiles of the two fluids also plotted in Figure 6. This translates to a pump power consumption reduction of up to 40% at 0°C. Summary & Conclusions A direct cooled battery module with heated representative cells was tested and simulated at a variety of conditions in the Castrol Thermal Rig with Castrol ON EV Thermal Fluids. The direct thermal management system was able to maintain low inter-cell and intra-cell temperatures of ~1.2°C even under ultra-fast charge conditions which has been shown to contribute strongly to battery durability. Correct fluid selection is important to maximise system efficiency while maintaining thermal performance. Fluid pump power consumption was reduced by up to 40% when a lower viscosity fluid was used. The simulated cell temperatures accurately correlated with the rig testing. Both the rig and simulation model are now verified tools that can be confidently used for the selection of battery thermal management fluids. Figure 4 – Full-Scale Module – Nine Heated Cells Figure 5 - Average measured intra-cell temperature delta & details of heated representative cells Figure 6 - Reduction in pressure drop with Fluid 2 at 79% flow plotted with fluid viscosity
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