Assessment of the performance of evaporation suppressant films: analysis and limitations of simple trialling methods

Hancock, N. H. and Pittaway, P. A. and Symes, T. W. (2011) Assessment of the performance of evaporation suppressant films: analysis and limitations of simple trialling methods. Australian Journal of Multi-Disciplinary Engineering, 8 (2). pp. 157-168. ISSN 1448-8388

Abstract

The potential utility of monomolecular layers ('monolayers') and other surface film materials for the reduction of open water evaporation has long been argued. However, outside the laboratory, trials to quantify the effectiveness of artificial surface films have produced highly variable results after application to water surfaces, whether natural water bodies or managed farm storages. This paper briefly reviews the physical mechanisms involved in evaporation suppression and the biophysical literature on aquatic surface microlayers. The wide-ranging results from sixteen months of outdoor trough-scale and (simultaneous) replicated bucket-scale evaporation reduction trials are interpreted using biophysical measurements made on microlayer and immediate subsurface water samples taken from the experimental troughs. When the prevailing environmental conditions and other ancillary measurements are taken into account, plausible hypotheses arise to account for at least some of the observed trial-to-trial differences in evaporation reduction and surface film performance. Results for the commercial monolayer product are inconclusive, as the concentration of the active ingredient in its formulation lacked the uniformity required for the accuracy at which these trials were conducted. Results for the temperature differential between open (unprotected) water and film-covered water, and the influence of windspeed on evaporative loss, indicate that the mechanism of evaporation suppression for mono-molecular (monolayer) organic films differs from that for thicker silicone oil films. These results have implications for both small-scale trialling of evaporation suppressants and the deployment and management of artificial surface film materials on agricultural water storages. In addition, it concluded that despite the attractiveness of simple side-by-side comparisons of performance, meaningful interpretation of results must consider prevailing meteorological conditions, and a timescale of hours rather than days.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to published version due to publisher copyright policy. © The Institution of Engineers Australia, 2011.
Depositing User: Assoc Prof Nigel Hancock
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Electrical, Electronic and Computer Engineering
Date Deposited: 05 Mar 2012 02:48
Last Modified: 03 Jul 2013 01:06
Uncontrolled Keywords: evaporation; suppressant films; monlayers; microlayers; aquatic surfaces
Fields of Research (FOR2008): 03 Chemical Sciences > 0306 Physical Chemistry (incl. Structural) > 030603 Colloid and Surface Chemistry
07 Agricultural and Veterinary Sciences > 0799 Other Agricultural and Veterinary Sciences > 079901 Agricultural Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)
09 Engineering > 0999 Other Engineering > 099901 Agricultural Engineering
Socio-Economic Objective (SEO2008): D Environment > 96 Environment > 9609 Land and Water Management > 960999 Land and Water Management of Environments not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/20883

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