Theoretical Foundations of Chemical Engineering最新文献

High-speed video recording methods are used to track the mass distribution patterns of composite droplets (consisting of two immiscible liquids: a core and a shell) by the deformed surface of a receiving liquid in the impact and intrusive modes. Flow modes are determined by the ratio of the kinetic and surface potential energies of the droplet at the moment of contact (free-fall height and droplet diameter). The droplet core consists of an aqueous solution of alizarin ink and the film material is sunflower oil. In the intrusion mode, the shell is maintained for a short period of time and the droplet sinks as a solid with minor deformations. In the intrusive mode, the impact of homogeneous droplets differs from the sectoral structure of the material distribution with thin horizontal periodic elements.

Coordination compounds of inorganic cations with biologically active substances are of considerable interest because they have better defined pharmacological properties than do free ligands. Immobilization of coordination compounds in ion exchangers makes it easier to reach required pharmacokinetics, offers significant prospects in issues related to the conservation and storage of bioactive substances, and allows for targeted delivery of an active component to a site of disease. Previously, we studied ligand sorption of pyridine-3-carboxylic acid from aqueous solution on the Cu(II) form of the Dowex-50 cation exchange resin. The purpose of this work is to demonstrate the feasibility of immobilizing pyridine-2-carboxylic acid and copper(II) in a Dowex-50-type styrene divinylbenzene-based sulfonic cation exchange resin; investigate the equilibrium distribution of the components between the Dowex-50 sulfonic cation exchange resin and an aqueous solution containing pyridine-2-carboxylic acid and copper(II) cations; and demonstrate the feasibility of precalculating the equilibrium composition of an aqueous solution of a pyridine-2-carboxylic acid + copper salt mixture for obtaining a Dowex-50 sulfonic cation exchange resin counter ion composition, which is of interest for optimizing industrial processes for the preparation of encapsulated drugs based on pyridine carboxylic acids and inorganic cations. The equilibrium distribution of the components between aqueous pyridine-2-carboxylic acid and copper nitrate solutions and Dowex-50 sulfonic cation exchange resin has been studied by a dynamic method at a temperature of 298 K. With allowance for the concentrations of the components in solution and their ability to participate in cation exchange reactions, the working pH range of the equilibrium solutions was chosen to be 2.0–2.5. The results we obtained lead us to conclude that, in multicomponent heterophase systems consisting of the Dowex-50 sulfonic cation exchange resin and aqueous pyridine-2-carboxylic acid and copper nitrate solutions, equilibrium complexation and ion exchange reactions take place. We demonstrate that, using selectivity coefficients of binary ion exchanges and [H₂L]⁺ and [CuL]⁺ complexation constants, one can precalculate equilibrium ionic compositions of the solution and Dowex-50 sulfonic cation exchange resin. The Dowex-50 sulfonic cation exchange resin can probably be proposed as a container for the preparation of medications based on pyridine-2-carboxylic acid and copper(II) cations.

High-speed video recording methods are used to track the distribution patterns of compound droplets (consisting of two immiscible liquids: a core and a shell) over the deformed surface of a receiving liquid in the impact mode, where the droplet’s kinetic energy at the moment of contact with the receiving liquid is significantly greater than the surface potential. The droplet core is an aqueous solution of alizarin ink and the film substance is sunflower oil. This contrasts with the impact of homogeneous droplets in a sectoral structure of the distribution of the substance with thin horizontal periodic elements.

The problem of the motion of a fluid layer over a solid substrate inclined at an angle to the horizontal is studied. The classical equation [3] that relates the fluid flow rate and the thickness of the flowing layer has long been known. This equation was derived from an exact solution of the fluid-layer motion problem for the case of constant viscosity. For most common fluids, viscosity depends significantly on temperature. It is shown that if this dependence is represented by Padé approximants, then an exact solution of the problem under variable viscosity can also be constructed. Exact solutions of hydrodynamic problems play an important role in research and engineering applications. They are used in stability analysis of flows, for testing numerical methods and computational codes, and for obtaining closed-form analytical expressions that determine integral characteristics of the process. An equation relating the thickness of the flowing layer and the fluid flow rate for variable viscosity is obtained; a comparison with the classical result is presented. It is noted that even moderate temperature variations lead to substantial changes in the flow rate due to viscosity variation. An equation for the thickness of a thin film is derived for the case where viscosity depends on temperature, analogous to equations previously obtained for constant viscosity. Under additional assumptions an exact solution of the derived equation is constructed.

The article presents research on the development of a composite material with improved performance. The growing industrial and academic interest in the selection of wood flour as a reinforcing filler in polymer composites and its preference over synthetic fibers is based on their superior mechanical properties, low density, abundance, and recyclability. With the aim of improving interfacial adhesion between the matrix and filler, various processing aids have been used to improve compatibility. Wood polymer composites (WPC) have been made from wood flour and four types of plastics, such as polyethylene, polystyrene, ABS (acrylonitrile butadiene styrene), and SAN (acrylonitrile-styrene copolymer). Experimental studies have been carried out using impact strength and tensile and compressive strength tests, as well as measurements of the expansion coefficient over the water absorption thickness. The effect of various technological additives on the mechanical properties of composites has been studied. The results show that processing aids can increase the bond strength of wood flour to the polymer and improve the mechanical properties of the composites. Comparatively better results are obtained using a processing aid in the form of an isocyanate resin. The wood–polymer composite combines the properties of wood flour and polymer, with water resistance, dimensional stability, and dynamic strength.

Ionic liquids with N-alkylpyridinium cation and dicyanamide anion are synthesized. The structure of the obtained compounds is confirmed by IR spectroscopy data. Studies of the electrical conductivity of dilute solutions in acetonitrile at 25°C are carried out. Based on the conductometric data, using the Lee–Wheaton method, the ionic association constants K_a, the limiting molar electrical conductivity (λ₀), and the standard Gibbs energy of association (ΔG⁰) in acetonitrile solutions are calculated.

Impact flow patterns of freely falling water droplets and aqueous solutions of ink and electrolytes in direct and reflected light are studied using high-speed video recording. The classification of the flow modes (and the set of components) is determined by the ratio of the kinetic and surface potential energies at the moment of droplet contact with the receiving liquid: intrusive at low velocities, transitional at comparable energy values, and impact. The intrusive mode involves a smoothly flowing intrusion, which then develops into a vortex ring. The impact mode is characterized by the formation of a thin transition layer containing ligaments and a discrete distribution of the droplet material on the cavity walls.

Development and modernization of equipment for processing bulk materials is a challenge that cannot be resolved without using adequate models of mixing processes. The paper presents a mathematical model of the mixing process in a new continuous-action drum-screw step mixer, which allows calculating the concentration fields of each component of the mixture in the working volume of the device. The model is based on a system of continuity equations for component concentrations. The shape of the volume occupied by the bulk mass in the steady-state mode of mixer operation and the fields of material movement velocity are modeled using simplified concepts based on experimental observations of the operation of gravity-driven drum-type mixers. When such mixers operate in the roll mode, the cross-section of the working volume occupied by the bulk material is divided into two zones. In the lower, transport zone, the material particles rise upward along the flow lines coinciding with the arcs of circles. In this case, the particles do not move from one flow line to another. Having reached the avalanche line, the particles enter the upper avalanche zone, where they enter the avalanche-like flow and roll down under the action of gravity, entering the transport zone again at the bottom of the avalanche line. In the presented model, it is assumed that the avalanche line coincides with a segment of the straight line inclined to the horizon at the avalanche angle of the bulk material. The model allows for mixture segregation and the effect of additional working elements—mixing blades—on the material flow. The concentration fields of the mixture components according to the proposed model can be calculated using known numerical methods for solving systems of partial differential equations.

Obtaining high-quality mixtures of solid dispersed polymer components in a special rotary device, as a preliminary stage of their processing before loading into a casting machine, contributes to compliance with the regulatory indicators of the 3D printing product, including color rendering, strength characteristics, etc. This process of mixing polymer media acquires particular relevance when using secondary raw materials. The formation of an engineering technique for calculating the main parameters of a rotary mixer of secondary and primary polymer dispersed materials (from the IV flowability class according to the Kerr classification) in a specified volumetric ratio is the goal of this study. The proposed method of rotary mixing of these media in crossing flows involves their separate feed using two units “mixing drum with rectangular blades–fixed relief platform” (stage 1) into the operating zone of the apparatus, in which the formed flows of heterogeneous particles are reflected from inclined baffles (stage 2). The specified blades are fixed on the surfaces of the drums in rows with angular displacements. The theoretical basis for the method of calculating the rational limits of change in the parameters of rotary mixing of polymer components is stochastic models of the studied process at stages 1 and 2 with allowance for the design features of the mixing units of the apparatus and the physical properties of the processed solid dispersed polymer components. When calculating the limiting values of the main operating parameters (angular rotation speeds of the mixing drums), a modification of the Froude criterion is adopted. In the paper, the block diagram for calculating the sought rational limits of change in a number of design parameters of the mixing drum, its blades, the relief platform for the units of the apparatus, and the corresponding inclined reflective surfaces (baffles) is described.

Periodic flows propagating along the interface between two viscous, stratified, weakly compressible fluids are analyzed. Analytical complete asymptotic solutions of the dispersion equations are constructed using the methods of the singular perturbation theory, which determine both the large-scale waves and the fine-structured ligamental components of the flow. It is shown that an additional class of singular solutions arises in the three-dimensional problem and disappears in the two-dimensional one; this class describes the additional ligament component of the periodic flow.