Simulation examining the factors influencing capillary wick transport in a refrigerant direct cooling system for power battery packs.

The effectiveness of power battery refrigerant direct cooling systems of electric vehicles incorporating capillary wicks is directly determined by these wicks' transport performance. The Fries-Dreyer equation describes wicking behavior, but there is a significant gap between its predictions and the experimental results as reported in the literature. This work examines the factors influencing transport performance in an unconsolidated capillary wick with spherical particles. A mathematical and physical model is developed, the latter using the COMSOL software platform. Both the developed mathematical form and the numerically simulated results of this model are closer to the experimental results than those obtained using the Fries-Dreyer equation. The simulation results enable optimizing the equilibrium height and capillary time numbers providing a fitted Fries-Dreyer equation that is then used to analyze the influence of saturation, inclination angle, wick particle diameter, and tortuosity on the liquid rise mass and velocity and the equilibrium height, and the effects are in close but not perfect accord with experimental data. To narrow the gap, the Fries-Dreyer equation is further optimized using the numerically simulated results, substantially improving the accord with the experimental results.