Перегляд за Автор "Bondar, Vladimir"

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Improving of thermohydraulic method for calculation of steam contact heat and mass exchange equipment
(2023) Bondar, Vladimir; Zaporozhets, Oleksandr; Sapiga, Victoria
Introduction. The complexity of determining the contact surface of phases and the boundaries of the continuous structure of liquid jets complicates the calculation of phase-contact heat and mass exchange mixing apparatuses. Materials and methods. The condensation process of water steam from a steam-gas mixture on a cylindrical free-falling liquid jet is considered under counter-current movement of the steam phase within a range of flow parameters characteristic of the food industry. Results and discussion. An empirical dependence for determining the onset of jet structure destruction adequately describes the process of its structural changes and is characterized by the fact that an increase in the Reynolds number leads to an increase in the critical height of jet destruction: the jet becomes more resistant to the action of the steam flow. With an increase in the dynamic pressure of the steam flow, corresponding to an increase in the Weber number, which characterizes a sharp decrease in the dimensionless height of dispersion, the jet intensively disintegrated, was destroyed at the outflow point, and was carried away by the steam flow. An original system of dimensionless similarity numbers, based on the results of jet hydrodynamics analysis, allows for determining the temperature change along the jet's length, taking into account the geometric characteristics of mixing heat exchanger distribution devices, flow geometric dimensions, steam-liquid flow parameters, and the thermophysical properties of the media. Empirical dependencies of the heat exchange process, considering the critical height of the existence of the continuous jet structure, are recommended for use in the thermohydraulic calculations of direct phase-contact heat exchange equipment. Conclusion. The novelty of the results lies in the introduction of empirical dependencies for calculating heat exchange, considering the critical height of the existence of the continuous structure of the liquid jet.
Thermodynamic analysis of the thermal-technological complex of sugar production: criteria for energy efficiency of an enterprise
(2021) Samiilenko, Serhii; Bondar, Vladimir; Piddubnyi, Volodymyr; Bilyk, Olena; Shutyuk, Vitaliy; Fedoriv, Viktor
A procedure for analyzing the effectiveness of using fuel and energy resources (FER) in sugar production, based on the developed idealized circuit of the thermal-technological complex (TTC) as the base for comparison was presented. This procedure makes it possible to quantify the level of perfection of existing and proposed thermal circuits, as well as the impact of measures for enhancing energy efficiency on their perfection. By idealizing technological and energy processes, a hypothetical TTC was synthesized, for which the minimum possible energy and entropy characteristics are determined. Under these conditions, the minimum possible heat consumption for the implementation of technological processes according to the classical heat technology circuit was calculated – 118.40 MJ/t; a "minimum" total increase in entropy from irreversible processes of the HTC – 314.68 kJ/(t•K); a minimum complex magnitude of specific consumption of conventional fuel – 0.8 % to m. b. The determined characteristics are absolute criteria for the efficiency of sugar production systems, since it is impossible to reach lower values under existing technology, quality of raw materials and other conditions. The content of the criteria of energy efficiency of TTC was stated and the system of coefficients was proposed: coefficient of total energy efficiency of the TTC, coefficient of energy efficiency of the system of heat supply of the technological processes and coefficients of energy efficiency of internal and external structures of the TTC. The proposed criteria provide an objective and thermodynamically correct characteristic of the TTC of different structures. The presented results of analysis of various measures for increasing the energy efficiency of sugar production show that only a gradual comprehensive reconstruction of an enterprise makes it possible to consistently reduce the FER consumption for technological needs, approaching the boundary values.
Thermodynamic analysis of the thermal-technological complex of sugar production: the energy and entropy characteristics of an enterprise
(2020) Vasylenko, Sergei; Samiilenko, Serhii; Bondar, Vladimir; Bilyk, Olena; Mokretskyy, Vitaliy; Przybylski, Wlodzimierz
This paper reports the approbation of a procedure of thermodynamic analysis of the thermal-technological complex of sugar production using the analysis of an enterprise of typical configuration as an example. Currently, the thermodynamic analysis of sugar production systems is mainly performed on the basis of a classical energy method. Minor attempts to exploit the potential of the second law of thermodynamics in the form of the adaptation of an exergy method are not systemic. Underlying the applied procedure is a joint analysis of general synthetic and analytical balances of mass, energy, and entropy. Such a procedure makes it possible to quantify the level of perfection of the existing and proposed thermal circuits, as well as the impact exerted on their perfection by energy efficiency measures, and it could be applied both to optimize the energy characteristics of the existing ones and in designing new enterprises of the sugar industry. It has been shown that the thermodynamic analysis of the thermal-technological complex of sugar production as a single system makes it possible to analyze the main factors of influence on the energy efficiency of the complex disregarding the course of the processes implemented therein. Such an approach can also be effectively used for the quick evaluation of the thermodynamic perfection of an enterprise and for determining its «energy-saving potential». Based on the results of energy analysis, the relationship has been established between the fuel and energy resources, supplied to the system, and the sources of their losses; a set of measures has been proposed to reduce the impact of each of these factors on resource consumption. Entropy analysis has revealed the internal and external causes of the irreversibility of processes; the principle of «energy irreversibility compensation» has made it possible to compile a rating of major imperfections and determine the optimal sequence of resource-saving measures. The results of the analysis have confirmed the efficiency of the procedure, which allows a comprehensive study, while operating only with the fundamental laws and the principles of classical thermodynamics, as opposed to procedures, based on energy-exergy characteristics
Thermodynamic analysisof sugar production heattechnological complex:analysis method
(2020) Vasylenko, Sergei; Samiilenko, Serhii; Bondar, Vladimir; Bilyk, Olena
The object of research is the heat-technological systems of sugar production and the heat-technological complex as a whole. A modern sugar factory is a complex hierarchical system of inextricably interconnected elements, and its basis – a heat-technological complex – combines the elements of technological, heat transfer, and mechanical equipment, in which complex physicochemical processes are simultaneously realized, closely interacting. Given the complexity of the internal relationships of processes, their parameters and characteristics, it is necessary to systematically approach the analysis of real functioning, performance evaluation and the solution of optimization problems of the complex as a whole, as well as its individual subsystems and elements. In this work, it is proposed a method for thermodynamic analysis of the heat-technological complex of sugar production as a single thermodynamic system, which allows to analyze the main factors influencing the energy efficiency of the complex regardless of the course of processes implemented within the system. The methodology is based on a joint analysis of the general synthetic and analytical balances of mass, energy and entropy. This model has a deep physical foundation, because the material balance equation is an integral form of the law of conservation of the quantity of matter, the energy balance equation is an integral form of the first law of thermodynamics, and the entropy balance equation is an integral form of the second law of thermodynamics. The main objective of the methodology is a quick assessment of the excellence of the heat-technological complex and its definition of “energy-saving potential”. Also, the application of the principle of energy compensation of irreversibility and entropy criteria allows to determine the sources and causes of system imperfections, and imperfections are compiled to help develop a system of measures to increase the efficiency of the optimal sequence complex. Therefore, the proposed methodology of thermodynamic analysis, in contrast to the methods based on exergy characteristics, provides a comprehensive analysis, operating only with the fundamental laws and principles of classical thermodynamics. It can also be used both to optimize the energy characteristics of existing ones and to design new sugar industry enterprises
Water retention capacity of sugar beet pulp dried by various methods
(2015) Ivashchenko, Natalia; Shutyuk, Vitaliy; Bondar, Vladimir; Ryabchuk, Alexander
Dried sugar beet pulp should become one of the main ingredients of cattle forage in Ukraine, and so production of such pulp is a very important task, given the necessity of processing by-products of the sugar industry in the absence of large cattle-breeding complexes. Materials and methods. Fresh sugar beet pulp has been used as a food product in a form of an extracted chopped straw of 50 micrometers to 1 mm, with the moisture content of 76 to 80 %. Researches with application of the convection drying method have been conducted in the DNG-9035A drying cabinet. The water retention capacity was determined as a ratio of the amount of water retained by the fibres and remaining in the test tube after centrifuging, and the corresponding amount of dry substances (accuracy ±1 g of water/g of dry substances). Based on the conducted experiment analysis, it has been determined that the pulp dried by the low-temperature method mostly swells in the first 15 to 20 minutes. Within this time period, soaking up to the recovery coefficient β = 0,84…0,89 takes place. The maximum value of the recovery coefficient amounts to 0,93 per 30 minutes for the pulp dried with hot air at the temperature of 100 °С. As a result of conducted experiments, we have determined that the granulated pulp dried under such method swells within the first 20 minutes, whereas the pulp shreds swell within the first 80 minutes. Within this time period, soaking up to β = 0,69 takes place. The maximum value of the granulated pulp recovery coefficient amounts to 0,76 per 35 minutes. However, afterwards, due to mechanical damages in the process of granulation, the product loses its shape completely, and turns into a liquid powder concentrate. The maximum value of the pulp shreds recovery coefficient amounts to 0,78 per 105 minutes. An excessive heat strain per each unit of the material causes considerable destruction of the capillary porous pulp structure, and formation of a crust on the surface, therefore moisture penetration into the material is complicated, and so the liquid interacts with the solid material structure quite slowly. Moisture does not penetrate into destructed cells, and fills open capillaries and pores of the material only. More destructed structure of the pulp facilitates renewal of initial properties as a result of moisture absorption. However, the ability to absorb moisture after drying is one of the necessary conditions determining the quality of final product.