Numerical investigation of the saturation effect on wick dry-out in a capillary driven evaporative cooling system

Abstract

The influence of gravity in vertically oriented capillary-driven evaporative cooling systems utilizing porous structures in devices such as heat pipes, vapour chambers and direct wick-based cooling is nontrivial. This can impede the rise of liquid through the structure, diminishing wick saturation. Here we developed a model to quantify the variation of saturation in a vertically oriented porous structure operating at low heat fluxes, with a focus in their use in evaporative cooling of batteries. The model was validated within 15% of the experimental data, and a parametric study was conducted to assess the impact of wick parameters on saturation. Dry-out height and dry-out heat flux were also determined across a range of heat fluxes and wick thicknesses, considering various porosities. Findings indicate that saturation increases with increasing porosity and wick thickness, while decreasing with increasing particle diameter. Furthermore, as porosity and wick thickness increase, the thermal conductive resistance of the wick experiences a substantial increase. Wick porosity has the most significant influence on dry-out height, saturation, and thermal conductive resistance. These insights are valuable for designing capillary-driven evaporative cooling systems operating under gravity.