Author(s): David Busuttil; William Peirson; Gregory Lee; Pou Onesemo; Chris Waite
Linked Author(s):
Keywords: Evaporation; Farm dams; Surface sheltering; Adhesion; Capillarity
Abstract: Loss of water resources due to evaporation is an issue of ongoing concern in Australia. Evaporation mitigation devices are being developed. These include floating units of various shapes which reduce the exposed evaporative surface area. This paper describes a preliminary evaluation of the effectiveness and efficiency of floating modular devices with different surface textures and therefore different magnitudes of adhesion between these device surfaces and water. Some materials with high adhesion to water, will draw up the water onto the device, whereas other materials are not easily wetted and will repel water. The evaporation experiments performed included an open water control test, and three floating modular device tests. The three devices were tennis balls; which represent hydrophilic materials, smooth polyethylene balls; which represent hydrophobic materials, and smooth polyethylene palls with a slime-mould growth; which represent hydrophilic materials which have aged and acquired a biological surface growth. Once essential corrections to ambient relative humidity and temperature effects were included, analysis of the test results showed that floating tennis balls increased the amount of evaporation by a factor of 1.33, whereas both the clean and slime-mould coated polyethylene balls reduced the rate of evaporation by about 65%. It was possible to quantify an adhesion coefficient to account for the increase in evaporation with respect to the planar surface area of water. These factors were 4.5, 2.1 and 2.0 for the tennis ball, smooth polyethylene ball and slime-mould coated polyethylene ball tests respectively. The impacts of adhesion are significant and need to be considered in the assessment of strategies to mitigate evaporation at the surface of open water bodies.
Year: 2011