Enhancing immersion cooling performance: Focusing on cooling fluid properties and battery cell arrangement angle

• Candidate immersion cooling fluids were quantitatively evaluated using the figure of merit (FOM). • Enhanced cooling effect using lower-viscosity fluid under identical power consumption. • Cooling performance analysis by varying cell arrangement in a fixed-size battery pack. • Increased cell arrangement improves cooling performance by reducing the average pack temperature and the number of thermally vulnerable cells. • Increasing the cell arrangement angle improves cooling efficiency by extending coolant residence time and suppressing bypass flow within the battery pack.