The Concept of a Dew Collection Device Based on the Mathematical Model of Sliding Liquid Drops on an Inclined Solid Surface

Dew collection, and devices for such, may play an important role in regions of our planet that are arid and lack clean water. Usually, dew collection devices are represented as an inclined plane, which is a trivial topology. In this work, we first propose the concept a dew collection device with a helicoidal structure in order to increase its surface area, and we suggest taking into account Frenkel’s mathematical model of sliding drops on an inclined surface as the fundamental idea in designing dew collection devices. We also believe that in the future this mathematical model can be used to investigate the possibility of condensing liquid drops within other planets’ atmospheres that contain hydrogen and oxygen. Finally, we represent our concept as a three-dimensional Rhino model.

Our planet contains many sources of fresh water that are distributed heterogeneously. While some countries, such as Canada, Russia, the USA, Latin American countries, etc., have a surplus of fresh water, most African countries suffer from a lack of fresh and clean water. The structure of some African land can cause rivers to turn into streams of mud, resulting in a high-level of infections, poor harvests and, consequently, malnutrition and high mortality.

Many deserts in Africa are located near the coast, where rainfall is very low but humidity is relatively high. These regions can be considered effective for the collection of dew, which is water in the form of droplets that appear on thin, exposed objects in the morning or evening due to condensation.

Nilsson et al. [1] investigated the possibility of implementing a dew collector to condense atmospheric water vapour using the radiative cooling effect – in particular, they studied the use of pigmented polymer foils with high solar reflectance and high thermal emittance. Nilsson [2] believes that moisture in the air can be condensed as dew and used not only for drinking but also for irrigation. Based on the experiments carried out in Sweden and Tanzania, his paper concerns observations of dew formation on radiatively cooled pigmented polyethylene foils. Similarly, Gandhidasan et al. [3] studied dew formation on radiatively cooled pigmented polyethylene foils.

Jacobs et al. [4] proposed a 1 m2 insulated planar dew collector, set at a 30° angle between the collector and ground, and a dew collector in the shape of an inverted pyramid, which was constructed to reduce the view angle to the night-time sky. They found that the pyramid collector design was able to collect about 20% more dew than the inclined planar collector. A more sophisticated method of dew collection was proposed by Nikolayev et al. [5], who revised previous approaches in the light of recent investigations considering the basic physical phenomena involved in the formation of dew.

Rajvanshi et al. [6] proposed a scheme for large-scale dew collection as a supply source of fresh water. The schematic requires cold seawater to be pumped from the neritic zone to a heat exchanger field. In addition, since it requires electricity for a pump, a wind-powered generator is used. Muselli et al. [7] investigated the relative contributions of dew and rainwater in the Mediterranean Dalmatian coast and the islands of Croatia, especially in the dry summer season. In addition, the authors evaluated the possibility of transforming roof rain collectors to dew water collectors as well.

Sharan et al. [8] determined the amount of dew water that could be collected with little investment by adapting plain, uninsulated, corrugated galvanized iron roofs that are common in most rural regions of India. Berkowicz et al. [10] measured dew water condensation in the city of Jerusalem using a condenser unit, such as the one in the Kothara village in India [8, 9] and reported a dew collection of 33 mm over a 12-month period from more than 176 dew events with a nightly maximum of 0.5 mm.

Beysens [11] reviewed the aspects related to heterogeneous nucleation and subsequent growth of water droplets, while condensation-induced water-drop growth on a super-hydrophobic spike surface was studied by Narhe [12]. Beysens et al. [13] experimentally studied dew collection from several passive foil-based radiative condensers and noted that chemical and biological analyses established that dew is generally potable.

The rest of this paper is organised as follows. Section 2 briefly reviews the model of a standard dew collection device. Section 3 discusses Frenkel’s mathematical model of liquid drops sliding down an inclined solid surface. Section 4 explains the geometry of a helicoid and provides its parametric equations. Section 5 proposes a new model for a dew collection device based on a helicoidal structure. Section 6 concludes our work and proposes some ideas for future works.

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