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Постійне посилання колекціїhttps://dspace.nuft.edu.ua/handle/123456789/7522
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Документ Heat Transfer in Down flowing Turbulent Evaporating Liquid Films with Developed Wavy Structure and co-Current Steam Flow(2016) Petrenko, Valentin; Zasiadko, YaroslavThe result of heat transfer modeling in down flowing turbulent films with the developed wavy structure at the regime of evaporation from film interface at free falling and with co-current steam flow, a heat transfer model, which takes into account a cyclic process of temperature field relaxation with the periodic mixing of film by big waves, has been presented. Temperature profiles along with the integral heat transfer coefficients (HTC) were obtained as a result of approximate solutions of heat transfer differential equations of in turbulent flows, adapted thus film flux with large surface waves, utilizing turbulent transport model by M. D. Millionschykov.Документ Heat Transfer Modeling Downflowing Laminar Films with the Developed Wavy Structure with co-Current Steam Flow(2016) Petrenko, Valentin; Zasiadko, YaroslavThe result of heat transfer modeling in down flowing viscous laminar films with the developed wavy structure at the regime of evaporation from film interface at free falling and with co-current steam flow, a heat transfer model, which takes into account a cyclic process of temperature field relaxation with the periodic mixing of film by big waves, has been presented. A mathematical model of heat transfer in laminar, heated to the saturation temperatures liquid films with the developed wavy structures on the free interface have been developed. The model takes into consideration cyclic relaxation of transient temperature field which happens right after the passage of a powerful big wave. The developed mathematical model describes the time history of the two dimensional temperature fields as a function of the Peclet number and the core characteristic of the wavy motion (the length of big waves). Based upon the proposed model a set of correlations have been obtained. These are proposed as a means for the generalization of heat transfer experimental data, obtained within the experimental studies of liquid films, heated to the saturation temperatures and evaporating from the interface. A generalized equation has been derived, which can be used for the calculations of Heat Transfer Coefficients (HTC) to the saturated sugar solutions liquid films.Документ Modeling of heat transfer in free down flowing laminar liquid films with development wavy structure at the regime of evaporation from the interface(2016) Petrenko, Valentin; Pryadko, Nikolai; Zasiadko, Yaroslav; Miroshnik, MariaA mathematical model of heat transfer in laminar, heated to the saturation temperatures liquid films with the developed wavy structures on the free interface have been developed. The model takes into consideration cyclic relaxation of transient temperature field which happens right after the passage of a powerful big wave. The developed mathematical model describes the time history of the two dimensional temperature fields as a function of the Peclet number and the core characteristic of the wavy motion (the length of big waves). Based upon the proposed model a set of correlations have been obtained. These are proposed as a means for the generalization of heat transfer experimental data, obtained within the experimental studies of liquid films, heated to the saturation temperatures and evaporating from the interface. A generalized equation has been derived, which can be used for the calculations of Heat Transfer Coefficients (HTC) to the saturated sugar solutions liquid films. This equation contains wavy characteristics of down flowing films and valid within the range of parameters characteristic for the sugar industry evaporators, namely: concentrations – 0…70 % dry matter; liquid mass flow rate density–0.01×10-3…0.6×10-3 m2/sec, the Peclet number range – 400…25000. The mathematical model of the temperature field cyclic relaxation turned out efficient for generalization of heat transfer experimental data not only laminar, but turbulent liquid films either, despite of the fact that the transport equations do not contain turbulent characteristics.Документ A study of water ice formation and melting processes on vertical cooled pipes(2016) Zasiadko, Yaroslav; Pylypenko, Oleksii; Forsyuk, Andriy; Gryshchenko, RomanThe use of cold accumulators based on the principle of water ice formation on the cooled surfaces during off-peak periods and water ice melting during on-peak periods is an effective method of electricity bills reduction. Within comparatively short periods of on-peak demand a noticeable amount of thermal energy related to ice melting is to be released, it becomes clear that not only sizing of ice accumulators based on balance calculations is actual, but also the determination of time periods of ice accumulation becomes critical. This work presents an experimental unit for obtaining data on the ice formation on the vertical cooled pipes and later on to continuously register data on the ice thickness diminishing at the regimes of ice melting when cooling of pipe stops. The data for ice formation and melting for some regimes have been presented and analyzed. The data form the base for deriving semi-empirical correlations allowing to determine time intervals necessary to generate of water ice layers of given thickness.Документ 3-D modeling of water flow and cooling down within the temperature range close to inversion point(2016) Gryshchenko, Roman; Zasiadko, Yaroslav; Forsyuk, Andriy; Pylypenko, OleksiiThe research and simulation of heat transfer during water refrigeration in the experimental section close to the vertical pipe which is cooled down considering abnormal character of water density change from the temperature in close to inversion point (+4°C) section were investigated. The graphs of water temperature velocity distribution throughout the height of experimental section were constructed and analyzed. The results obtained allow estimating the impact of water temperature that is closely situated to inversion point on the dynamics of water ice melting and generation as well as on the form factors of cold accumulators. Such software and analytical research will allow increasing effectiveness and efficiency at the heat and bulk transfer equipment engineering.Документ Experimental and theoretical study of ice formation on vertical cooled pipes(2015) Zasiadko, Yaroslav; Pylypenko, Oleksii; Gryshchenko, Roman; Forsyuk, AndriyDynamics of ice accumulation on the surface at different ∆t (refrigerant evaporation temperature and the temperature of water that overflows surface) has been studied. Series of experiments have been carried out with 2 refrigerants (R12 and R22). The temperatures of water and that of refrigerant evaporation have varied within the intervals +1,5÷+4,50C; -10÷-200C, respectively. The mass flow rate and the velocity of water within the experimental sections were kept constant during a whole series of experiments. The ice-layer thickness was measured by means of optical method. The instantaneous images of the experimental pipe with the ice layer were processed with the graphic processing software.