Porous media flow modeling

Flows in porous media play a role in many applications. Two relevant application areas are the drying of inkjet-printed droplets on paper and the flow in a heat pipe, which can for instance be used for cooling of high power density LED lighting. For inkjet-printed droplets on paper it is important to be able to predict the properties of the deposit layer after the liquid has evaporated. To this end we have set up a simulation program that describes the process after the droplet has been jetted, including evaporation of the liquid components, absorption of the liquid into the porous substrate and temperature effects. Also, multi-component droplets have been considered. For small contact angles a simplified model based on lubrication theory has been developed, for larger contact angles the full Stokes flow is considered. Until now, the porous substrate has been described by the Darcy equation, but in the future, the detailed structure of the porous substrate will be considered as well. Results agree well with experimental results for evaporating multi-component droplets, like in the movie below.

 

A heat pipe is intended to increase the heat transfer by using the latent heat of evaporation. Heat from a heat source is used to evaporate a liquid in a porous structure, the wick. The vapor condenses again in a different location and is transported back by the capillary action of the porous structure. A simulation program is being developed to predict the heat transfer properties of a heat pipe.