Перегляд за Автор "Lementar, Sviatoslav"

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Determination of the ejection coefficient of a jet apparatus with a conical-cylindrical mixing chamber
(2023) Tymchenko, Ivan; Ponomarenko, Vitalii; Lementar, Sviatoslav; Yakobchuk, Roman; Liulka, Dmytro
Ejectors have found wide application in various industries due to their simplicity, unpretentiousness to operating conditions, absence of tribological problems, etc. Their main drawback is related to the low efficiency, which is at the level of about 30%. The need to improve operational characteristics led to the creation of an innovative ejector with a combined mixing chamber (initial conical and subsequent cylindrical parts). A mathematical model based on balance equations is proposed for the possibility of determining the ejection coefficient (the main flow rate characteristic) when designing or auditing equipment
Influence of gas-dynamic parameters of the heat carrier on the efficiency of drying peas in rotary dryers with a fluidized bed
(2020) Yakobchuk, Roman; Lementar, Sviatoslav
Introduction. The aim of the research is determination the influence of gas-dynamic parameters of heat carrier movement in the chamber of a rotary drying unit with a fluidized bed on the efficiency of the peas drying process. Materials and methods. The research was carried out on an experimental drying unit with a conical element installed in the drying chamber, and with the help of 3D models of drying units. The simulation of the heat carrier movement was performed using CFD methods, followed by verification in a pilot plant. Results and discussion. It is established that the heat carrier speed in the drying chamber without a conical element is in the recommended limits (1.8–2 m/s) only in the range from 0 to 0.7 m in the height of the chamber. The zone from 0.7 to 1.2 m is used less efficiently, because the velocity of the heat carrier is in the range of 1.65–1.8 m/s. The reason for this is that when the heat carrier passes through the wet product, its temperature decreases, it leads to decreasing of heat carrier volume. This causes the destruction of the constant mode of heat carrier and consequently reducing of the intensity of drying of the product. In the drying unit with a conical element, the stabilization of the heat carrier speed is achieved within the recommended (1.8–2 m/s) limits along the entire height of the drying zone, which provides a constant height of the fluidized bed of product in the drying chamber. This creates the conditions for a higher intensity of drying the material and improves the quality of the dried product, because it does not stay for a long time in the high temperature zone. It is found out that with heat carrier speed increasing over 2 m/s there is a decrease in the efficiency of its potential. Thus at an initial speed of 2 m/s and an initial temperature of 100 C, its final temperature is about 55 C, which coincides with drying regulations for installations of this type. While increasing speed up to 2.2 and 2.4 m/s there is final temperature increasing of the heat carrier up to 58 and 60 C and as a result it reduces the efficiency of this installation. Conclusions. This research allows to determine the influence of the installation of a conical element in the drying chamber on the speed of the of heat carrier and its pressure in the drying zone, as well as the influence of the speed of the drying agent on its temperature in this zone.
Information technology in designing high-performance equipment for biomass compacting
(Rindyuk, D. Information technology in designing high-performance equipment for biomass compacting / D. Rindyuk, S. Lementar // Food and Environment Safety : journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava, 2013. – Vol. XII, Issue 2. – P. 115-122., 2013) Rindyuk, Dmitry; Lementar, Sviatoslav
The basic principles and methods of constructing a mathematical model for the processes of particular materials processing are presented in this paper. An example of the practical application of the developed model in the technology of biomass extrusion, which is used for the production of fuel pellets, is considered. A mathematical model of the process for particular materials extrusion is developed and a new approach to the extrusion granulator unit design is offered with the developed methods taken as a basis. The effect of technological and design factors of extrusion granulator unit to the extrusion process regularity are also studied.
Process of sugar solutions sulfitation in terms of hygienic requirements for equipment operation
(2022) Ponomarenko, Vitaliy; Sliusenko, Andrii; Liulka, Dmytro; Lementar, Sviatoslav; Forostiuk, Inna; Yakymchuk, Nikolai
Робота станції сульфітації на цукровому заводі пов'язана з порушенням санітарних вимог до виробничих приміщень через нестабільність обладнання. Виправити ситуацію можна комплексним рішенням: стабілізацією потоків і вдосконаленням конструкції струминного апарату. Метою дослідження є вивчення гідродинаміки реактивних апаратів. Матеріалом для дослідження є струминні апарати з дисперсним струменем рідини та гідродинамічні процеси, що відбуваються в камері змішування. Використовуються теоретичні (теорія доданої маси), експериментальні (загальноприйняті методи дослідження гідродинаміки течій), аналітичні (статистична обробка результатів) методи дослідження. Розроблено конструкції струминних апаратів з дисперсним струменем рідини та покращених експлуатаційних характеристик. На їх основі запропоновано обладнання для здійснення тепломасообмінних процесів у цукровій промисловості (сульфітатори). Показано можливість використання теорії доданої маси при розрахунку такого апарату, зазначено основні причини, чому розрахунок цим методом призводить до неточностей, знайдено коефіцієнт передачі енергії. Зроблено висновок, що складні взаємозв’язки між елементами ежектора та фізичними явищами в камері змішування та неможливість їх кількісного обліку не дозволяють на даний момент створити точну математичну модель його роботи. Наведено можливість застосування теорії доданої маси для розрахунку струминних апаратів з диспергованими струменями рідини та запропоновано нові конструкції струминних апаратів для використання в харчовій промисловості. Operation of the sulfitation station at a sugar factory involves violations of sanitary requirements for production facilities due to instability of the equipment. It is possible to correct the situation with an integrated solution: by stabilizing flows and improving the design of the jet apparatus. The aim of the research is to study the hydrodynamics of jet apparatus. Material for the study is the jet apparatus with a dispersed liquid jet and hydrodynamic processes occurring in the mixing chamber. Theoretical (the theory of added mass), experimental (generally accepted methods of studying the hydrodynamics of flows), analytical (statistical processing of results) research methods are used. Designs of jet apparatus with a dispersed liquid jet and improved performance characteristics are developed. On their basis, the equipment for carrying out heat and mass transfer processes in sugar industry (sulfitators) is proposed. The possibility of using the theory of added mass in the calculation of such apparatus is shown, the main reasons why the calculation by this method leads to inaccuracies are noted, and the energy transfer coefficient is found. It is concluded that complex relationships between the elements of the ejector and physical phenomena in the mixing chamber, and the impossibility of their quantitative accounting do not allow creating an accurate mathematical model of its operation so far. The possibility of applying the theory of added mass to the calculation of jet apparatus with dispersed liquid jets is presented, and new designs of jet apparatus for using in food industry are proposed.
Simulation of nanoparticle aggregation processin heterogeneous dispersed systems
(2020) Olishevskyi, Valentyn; Vasylenko, Sergei; Babko, Evhen; Lementar, Sviatoslav
The stady of particle aggretion is relevant and stidied in chemical technology, biophysics, in solving problems of purification from aerosol or colloidal contaminants. The influence og nanoparticles on the aggregation kineticsds. The influence of nanoparticles on the aggregation kinetics of dispersed phases in suspension is considered. Models based on modifications of the particle dynamics method taking into account Van der Waals forces, gravity, Brownie and Stokes forces based on semi-empirical dependences for the rate of aggregation and disaggregation in collisions are used. Based on the analysis of the Smolukhovsky equation, molecular kinetic and localisotropic turbulence of Kolmogorov's theories, the dynamics of simultaneous turbulent and Brownian transfer to the process of "rapid coagulation" and the mechanism of influence of nanoparticles on their accumulative ability in colloidal heterogeneous dispersion are proposed. The developed equations for the rate of kinetic energy scattering in a suspension makes it possible to determine the particle dispersion in which the Brownian diffusion of particles in the coagulation mechanism predominates. This means, the more intense the process of mixing the suspension, the greater the role in the process of coagulation, precipitation and filtration play particles of the nanoscale range, which are included in the rapid movement of the vortex. These results are useful for practical application in control of intensity of coagulation processes in mixing devices. Conclusions. The mechanism of influence of nanoparticles on their aggregation ability in colloidal heterogeneous disperse systems is offered.
The method of determination of the optimal parameters of dispersed materials granulation through consolidation
(2012) Rindyuk, Dmitry; Lementar, Sviatoslav
The method of determination of the optimal constructive and technological parameters of dispersed materials granulation through consolidation is represented within the task of nonlinear mathematical programming. The method is based on mathematical modeling of dispersion materials extrusion through the granulator matrix holes. The method allows taking into account constructive features of technological equipment and rheological properties of the raw material.
The research of a one-step and two-step ejector with a compact and dispersed jet of liquid
(2017) Ponomarenko, Vitaliy; Liulka, Dmytro; Dimitrov, Tsvetan; Lementar, Sviatoslav; Khitriy, Yaroslav; Perekrest, Natali
The work of the jet sulphitator ejector of sugar production is analyzed. The tests of a gas-liquid ejector with a compact and dispersed liquid jet in a wide range of changes in geometric characteristics (1.3 ... 11.25) were tested on the test-bench at the laboratory and the range of their optimal values (4 ... 7), which allowed to reach the maximum ejection coefficient, was found experimentally. The ejection coefficient for an ejector with a compact liquid jet is 15 ... 20% lower than for an ejector with a dispersed jet at the same flow rates.The design of a new two-stage ejector with improved expendable characteristics is offered, the basic geometric dimensions are justified. An increase of the ejection coefficient without additional energy penalties is experimentally proved. The field of application of the offered design ejector is not limited to food industry and it is recommended to use in those cases where heat-mass transfer processes take place.
The research of the influence of temperature on the рrocess of granulation by extrusion
(2012) Rindyuk, Dmitry; Lementar, Sviatoslav
The process of extrusion pelletizing particulate materials, such as sunflower and buckwheat husk, oak and pine chips, wheat straw and bran has been considered. It was investigated the effect of temperature of raw materials, compacting pressure and the diameter of the press-matrix on quality of fuel pellets.