The retardation of water evaporation from the open water bodies using ultra-thin layers of polydimethylsiloxanes and water balance regulation at JSC "Halychfarm" (Lviv)
Students Name: Rehush Vladyslav Andriiovych
Qualification Level: master (ESP)
Speciality: Building and Civil Engineering
Institute: Institute of Civil Engineering and Building Systems
Mode of Study: full
Academic Year: 2022-2023 н.р.
Language of Defence: англійська
Abstract: Rehush V.A., Zhuk V.M. (supervisor).The retardation of water evaporation from the open water bodies using ultra-thin layers of polydimethylsiloxanes and water balance regulation at JSC «Halychfarm» (Lviv). Master’s thesis. Lviv Polytechnic National University, Lviv, 2023. Extended Abstract. The Master’s thesis is devoted to solving the scientific and technical problem of reducing evaporation from surface water bodies by using ultra-thin films of special high-molecular additives, namely polydimethylsiloxanes. The tendency of increasing the average annual temperature causes to a significant violation of the water balance of territories and water bodies due to a significant increase in water loss to evaporation [1], therefore the problem of the effectiveness of reducing water loss to evaporation requires a detailed study. As of 2023, the retardation of evaporation using ultrathin films of fatty alcohols, in particular cetyl-alcohol or hexadecanol (chemical formula C16H33ОН) and stearyl-alcohol or octadecanol (C18H37ОН) has been studied in detail [2–3]. An important practical disadvantage of fatty alcohols is their relatively high cost and low stability, which reduce the technical and economic efficiency of using protective films from fatty alcohols [4]. A potentially more effective way to reduce evaporation may be the use of ultrathin films of polydimethylsiloxanes (PDMS). The use of ultra-thin films of PDMS ensure a long-lasting effect, meet environmental requirements and are harmless to human health. Field studies in rice fields in Kenya demonstrated a positive effect of the use of PDMS-based Aquatain to control malaria mosquitoes [5]. The object of research is the retardation of evaporation from surface water bodies. The subject of the study is the effectiveness of reducing water evaporation when using PDMS films with a thickness of 1–100 microns. The purpose of the research is to obtain the time dependence of the main parameters characterizing the reduction in the rate of evaporation with the help of ultrathin films of PDMS-100 and PDMS-200 with a thickness of 1 ?m, to determine the dependence of mass transfer coefficients during evaporation on temperature. The dynamics of change over time of the daily values of the effect of reducing evaporation using PDMS films, as well as the total effect since the beginning of the study, were obtained. The maximum daily effects of reducing evaporation were obtained on the 6th day of research; they were, respectively, 39.5% for the PDMS-200 film and 32.9% for the PDMS-100 film. After the almost complete cessation of the evaporation reduction effect of PDMS additives at week 5 of the studies, starting from day 39, the evaporation reduction in containers with PDMS films steadily recovered, but at different levels. Thus, in the container with the PDMS-200 film, the daily effect varied from 6.4% on the 44th day to 30.9% on the 78th day of research, while the daily efficiency of the PDMS-100 film did not exceed 10.5%. Linear correlations were obtained between the values of the mass transfer coefficient and the temperature of the free surface for water without additives, as well as for similar containers with ultra-thin PDMS films of 1 ?m thick. Taking into account the long duration of the effect of reducing evaporation, ultra-thin films of polydimethylsiloxane, especially PDMS-200, from an economic point of view, can be a profitable alternative to the use of monolayers based on fatty alcohols. The efficiency of using PDMS-200 films to reduce the evaporation of water from the free surface of cooling ponds of the industrial water supply system of JSC "Halychfarm" (Lviv) in the period from June to October was considered. Keywords – water bodies, fatty alcohols, retardation of evaporation, polydimethylsiloxane, ultrathin films. References. 1. World Meteorological Organization. State of the Global Climate 2021. WMO-№ 1290/2022. 2022. P. 54 2. Retardation of Evaporation by Monolayers: Transport Processes. Ed. V.K. La Mer. Academic Press, New York. 1962. 277 p. 3. Saggai S., Bachi O.E.K. Evaporation reduction from water reservoirs in arid lands using monolayers: Algerian experience. Water Resources. 2018. Vol. 45, 2. P. 280–288. 4. Zhuk V., Rehush A., Burchenya S., Hrytsiv O. Long-term retardation of water evaporation by ultra-thin layers of polydimethylsiloxanes in the indoor conditions. Journal of Ecological Engineering. 2021. 22(8). P. 33–40. 5. Bukhari T., Takken W., Githeko A.K., Koenraadt C.J.M. Efficacy of Aquatain, a monomolecular film, for the control of malaria vectors in rice paddies. PLoS ONE. 2011. 6 (6), e21713. https://doi.org/10.1371/journal.pone.0021713.