Visnyk LNAU: Architecture and Farm Building 2020 №21: 56-60
RETARDATION OF WATER LOSSES ON EVAPORATION BY MEANS OF A LAYER OF POLYDIMETHYLSILOXANE
Zhuk V., Candidate of Engineering Science
National University "Lviv Polytechnic".
LLC "Association of Engineering Enterprises", Lviv
Rehush A. Candidate of Engineering Science
Lviv National Agrarian University
AnnotationThe increase in the average annual air temperature is a steady trend of recent decades both in Ukraine and in the world as a whole. Global warming causes a number of challenges and threats in the field of hydraulic and water engineering, the main of which is a significant violation of the water balance of territories and water bodies due to a significant increase in water losses due to evaporation. In recent decades, there has been an active search, testing and implementation of various methods to decrease water loss by evaporation, including systems of floating, suspended or modular coatings and coverings, adding polyacrylamide to water or special additives that form ultra-thin films on the free water surface, which are able to effectively increase the resistance to evaporation. Analysis of the results of previous studies indicates the prospects of using the monolayers of special additives to reduce water loss due to evaporation from the surface of reservoirs of different sizes and purposes. The most studied additives of this type today are fatty alcohols: cetyl alcohol (hexadecanol), stearyl alcohol (octadecanol) and their mixtures, which decrease water loss by evaporation by an average of 20−30%, in some cases − up to 50−60%. In recent years, there has been an active search for new, effective and cheaper additives to reduce evaporation; of particular interest in this direction are silicone oils − polymerized siloxanes, organosilicon fluids, which are widely used in lubrication systems, hydraulic drives, in medicine and cosmetology, in the food industry and others. In laboratory quasi-stationary conditions, a series of experiments on the effect on the evaporation rate of tap water of one of the promising types of special additives − polydimethylsiloxane PDMS-200 is fulfilled. As a result of a continuous 33-day experiment, a total reduction of evaporation water losses in a vessel with a 100 μm thickness film of PDMS-200 is obtained as 50.5% compared to a similar vessel without additives.
water evaporation, monolayer, silicone oil, polydimethylsiloxane, evaporation rate
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