Investigating the potentials and limitations of capillary-fed vapor generators: A heat and mass transfer study

Passive fluid transport, which plays a crucial role in a wide range of processes from engineering to biology field, is becoming increasingly attractive due to the prospect of a lower energy demand. Here, we focus the attention on passive thermal evaporation, which is considered an emerging and promising water treatment technique. In detail, we report an extensive theoretical study of capillary-driven fluid flow in hydrophilic and porous materials to be used as thermal evaporators in water treatment devices such as vapor generators or distillers. These materials are designed to spontaneously and properly soak up the water to be treated and absorb thermal energy, establishing a continuous vapor generation. Design guidelines are reported and extensively discussed with the aim of preventing dry-out phenomena, which could compromise the correct functioning of the component and limit the performance. The results presented here envision a potential component size on the order of meters, which is, to the best of our knowledge, two orders of magnitude more than the size effectively explored in the experimental tests reported in the recent literature. Moreover, this modelling framework may be leveraged to assist innovation actions on materials and/or manufacturing techniques, further increasing the competitiveness and the widespread deployment of passive and sustainable solutions.