Possible ways of constructing a general model of cavitation reactors are considered. A mathematical model is proposed that without using any limiting assumptions describes adequately the dynamics of vapor-gas bubbles and the behavior of a cavitation cluster in a wide range of regime parameters. In the framework of the model, the influence of gas content and liquid temperature on the cavitation intensity is considered. The possibility of modifying the model as applied to optimizing the operation of cavitation reactors is discussed.
The problem of drop deformation and breakup in shear flow represents academic and practical interest and has attracted close attention over the intervening decades. Drop breakup is important for a wide range of engineering and biomedical applications including production and processing of emulsions, aerosols, etc. Although drop breakup operations are widely used in various industries, however, till quite presently there is no unequivocal treatment of the physical mechanism, which causes the fragmentation of dispersions in shear flows. In this paper the principles of constructing a mathematical model, which predicts the evolution of initially spherical droplet in shear flows of viscous liquid over a wide range of flow regimes as well physical parameters of both liquid phases, are considered. A mathematical model is presented that describes the deformation of a single drop suspended in another immiscible liquid under the combined action of three forces, namely, hydrodynamic force, capillary force and dissipative viscous force. The influence of each of these forces on the process of droplet deformation is discussed in the paper. The focus of the study is to more deeply analyze the dynamics of droplet deformation in shear flows and the transitional effects associated with current droplet shapes. Particular attention is paid to the analysis of critical conditions for the onset of irreversible deformation of droplets, which leads to their destruction. The deformed droplet is assumed to be in the form of prolate ellipsoid of revolution. The drop deformation is regarded as motion of the centers mass of the half-drops, symmetrical with respect to the drop center. The results of numerical calculations for droplet deformation in shear flows in comparison with experimental data of other authors are presented. A simple criterion for destruction of droplets in shear flows has been obtained. The results of the analysis confirm the reliability of the model and the competency of the assumption made. The model is able to predict the nature of droplet deformation and the conditions for their destruction in shear flows with known operating parameters with a greater degree of accuracy than the existing empirical relationships.
Evolution of the cavitation cluster and the level of the dynamic cavitation effects in liquid flow within a Venturi nozzle, depending on the design features and the mode of operation of this type cavitator, are considered. The experimental and theoretical investigations have been performed with the view to using the Venturi nozzle as cavitation reactor to efficient influence supramolecular structures in liquid in relation to producing stable liposome dispersions. Structural peculiarities of liposomes, closed biological nanocapsules, as well as bond energy values in these structures have been analyzed. The results of this study prove that using Venturi nozzles in large-scale production of liposome preparations allows increasing production capacity and significant reduction in the mass-related power consumption as compared with traditional acoustic and hydrodynamic methods.
The article presents complete understanding of bacterial cell disruption process under hydrodynamical cavitation (HC) condition. Analysis of present literature has shown that the process of cavitation is widely used in the food, chemical, pharmaceutical, and biological industries and is effective from ecological and energy point of view. Novel studies presents mechanisms, which ascertain fact of complete or partially cell wall destruction, but not explain reasons of this. The article proposes mechanisms and their theoretical justification for the extraction and sterilization process, and the thermophysical parameters necessary for conducting a particular process are determined.
Creation of new composite granular fertilizers with layered structure, which are formed due to the layered mechanism of granulation in the granulator of the fluidized bed is an urgent task. The process of forming these granules is achieved due to the layered granulation mechanism, the basis of which is the formation of a layer of solids on the surface of the granules by mass crystallization. In the production of granular fertilizers based on ammonium sulfate with the addition of organic and inorganic impurities an important place is occupied by the processes of evaporation and mass crystallization, which determine the morphological properties of the obtained granular material. During the experimental study of the evaporation process, it was found that the process consists of three main evaporation periods: the heating period from the initial temperature to equilibrium, the period of equilibrium evaporation and the decreasing drying rate period with crust formation, during which a solid crystal structure is formed. The beginning of each period according to the example of drying droplets in a gas stream during spray drying is described by the nature of the change in droplet temperature. This paper presents the obtained thermograms of the process of evaporation of droplets with a diameter of 3–7 mm 40%, 50% and 60% aqueous solutions of ammonium sulfate with the addition of a mixture of bone meal. The evaporation of 40%, 50% and 60% solutions of ammonium sulfate with the addition of a mixture of bone meal, with a given ratio of AS: BM on a dry residue of 60:40 and 80:20 on a surface temperature of 95°C in the second evaporation period crystalline nuclei appear, and the concentration of solute is close to saturated and almost unchanged, so that the evaporation rate and temperature of the drop, as can be seen from the thermogram, remain constant temperature for all solutions of ammonium sulfate. Increasing the content of bone meal from 8 to 24% to shift the wet thermometer in the kinetics of the evaporation process. The paper also presents the results of morphological analysis of the obtained solid crystallized drops of ammonium sulfate with impurities of bone meal. It was found that the solid crystallized drop of ammonium sulfate with bone meal consists of a framework of microcrystals of ammonium sulfate, with a reduced size of 10 to 80 μm, bone meal in the form of inclusions is placed in the frame, the particle size of bone meal varies up to 100 μm, indicating that the solution is a suspension.
A mathematical model is presented that describes the deformation of a single drop suspended in another immiscible liquid under shear flow. The deformed droplet is assumed to be in the form of prolate ellipsoid of revolution. The drop deformation is regarded as motion of the centers mass of the half-drops, symmetrical with respect to the drop center. The effects of viscid and capillary forces on the drop deformation accounted for in modeling with the aid of the mechanical Voight’s model. A simple criterion for destruction of droplets in shear flows has been obtained. The results of numerical calculations for droplet deformation in shear flows are presented in comparison with experimental data of other authors. It is shown that the model allows the prediction of behavior of deformed drops in shear flows over a wide range of flow regimes and physical parameters of the both liquid phases.
Analysis of the work, which considered the mathematical modeling of the melting process in various industries, currently does not pay attention to modeling the processes of heating and melting of hydrocarbon mixtures, such as vaseline, paraffin, fats, lanolin and others. The issue of optimization of heating and melting processes, calculations of necessary process parameters (speed and depth of thermal front penetration, etc.) and equipment, avoidance of repetition for each hydrocarbon mixture of experimental studies shows the need to develop a mathematical model of these processes. For the method of melting a substance placed in a cylindrical tank, based on the movement of a disc heating element under the action of gravity during melting and overflow of molten substance through the gaps between the disc and the walls of the tank, simulation has been carried out. Simulation of the melt flow in the annular gap is presented, which describes the laminar flow under the influence of the pressure drop and the velocity of the vessel wall relative to the heater, and the melt flow under the heater.
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