Investigation of the Process of Simple Distillation in Irrigated Pipe Elements

In modern chemical and oil refining complexes, separation processes are among the most popular and energy-intensive. Installations for their implementation should be equipped with nodes for creating vapor (evaporators) and liquid (deflegmators) irrigation. Evaporators of any type (film, thermosiphon, gas lift, cubic) belong to this class of devices. For example, in cubic evaporators, the gas flow is completely formed from flux bubbles that originate on the heat-conducting surface and float in the volume of the cubic liquid located in the apparatus. Due to the accompanying mass exchange, the bubbles are enriched with volatile components during ascent and noticeably increase in volume, and the growth of the bubble is determined, among other things, by the total flow. At the same time, in real bubbling-type equipment, the total mass transfer surface exceeds the cross-section of the device itself by more than two orders of magnitude. Thus, according to, the ratio of the internal cross-sectional area of the apparatus to the developed mass transfer surface is 0.0015–0.002. Based on the analysis of the integral equation of the diffusion boundary layer, it is shown that the presence of a resultant flow of substance through the phase interface (non-equimolarity of the process) in a two-phase gas (vapor)–liquid system leads to the transformation of the structure of the traditional mass transfer equation itself. The use of a new structure obtained for both binary and multicomponent mixtures makes it possible to significantly simplify the approach to the description and generalization of arbitrary mass transfer processes. The innovativeness of the proposed approach lies in its universality for non-equimolar processes. This simplifies the creation of models of any mass transfer devices and entire production lines. In addition, the proposed approach is a good auxiliary tool for various researchers and experimenters. It should also be noted that the separation processes of many products of organic origin during heating are characterized by the appearance of undesirable side reactions (thermal decomposition, condensation, polycondensation, formation of harmful impurities, etc.), which occur most intensively in the heating zones. At the same time, the evaporation and distillation units are subject to requirements for the minimum hydraulic resistance of the structure, the maximum separation capacity (efficiency), and the minimum residence time of the product in the apparatus (equivalent to the minimum holding capacity of the structure). It was noted that the specified requirements are most fully met by film-type devices.

NUMERICAL SIMULATION OF DUST POLLUTION OF WORKING PLACE NEAR COAL DUMP

The problem of estimating the level of air pollution in the working areas near the coal pile is considered. The task is to develop a CFD model that allows to predict the level of air dust pollution, taking into account the process of wetting the surface of the coal pile. To model the process of coal dust transfer in the air, a twodimensional mass transfer equation is used, which takes into account coal dust transfer due to convection and diffusion. The Navier-Stokes equations are used to calculate the air flow field near the coal pile. Finite-difference schemes of splitting are used for numerical integration of modeling equations. Computer code is developed on the basis of created CFD model. The developed code can be used to analyze the effectiveness of the coal surface wetting to reduce dust pollution of work areas near coal piles. The results of a computational experiment are presented.

Mathematical modeling diffusion of admixture particles in a strip with randomly located spherical inclusions of different materials with commensurable volume fractions of phases

The process of diffusion of admixture particles in a multiphase randomly nonhomogeneous body with spherical inclusions of different materials with commensurable volume fractions of phases is investigated. According to the theory of binary systems, a mathematical model of admixture diffusion in a multiphase body with spherical randomly disposed inclusions of different radii is constructed. The dense packing of spheres with different radii is used to modeling the skeleton of the body. The contact initial-boundary value problem is reduced to the mass transfer equation for the whole body. Its solution is constructed in the form of Neumann series. On the basis of the obtained calculation formula, a quantitative analysis of the mass transfer of admixture in the body with spherical inclusions, which are filled with materials of fundamentally different physical nature, but commensurable volume fractions, is carried out. It is shown that in modeling skeleton by spheres of one characteristic radius averaged concentration values coincide for different cases of radius, such as when characteristic radius equals to the average value of the radii of inclusions; or to the radius corresponding the smallest spherical inclusion; or to the radius of an order of magnitude smaller than this value.

Numerical Modeling of Heat and Mass Transfer during Cryopreservation Using Interval Analysis

In the paper, the numerical analysis of heat and mass transfer proceeding in an axially symmetrical articular cartilage sample subjected to the cryopreservation process is presented. In particular, a two-dimensional (axially symmetrical) model with imprecisely defined parameters is considered. The base of the heat transfer model is given by the interval Fourier equation and supplemented by initial boundary conditions. The phenomenon of cryoprotectant transport (Me2SO) through the extracellular matrix is described by the interval mass transfer equation. The liquidus-tracking (LT) method is used to control the temperature, which avoids the formation of ice regardless of the cooling and warming rates. In the LT process, the temperature decreases/increases gradually during addition/removal of the cryoprotectant, and the articular cartilage remains on or above the liquidus line so that no ice forms, independent of the cooling/warming rate. The discussed problem is solved using the interval finite difference method with the rules of directed interval arithmetic. Examples of numerical computations are presented in the final part of the paper. The obtained results of the numerical simulation are compared with the experimental results, realized for deterministically defined parameters.

EFFICIENCY EVALUATION OF THE HEAT DEPARAFINIZATION OF PRODUCING WELL EQUIPPED BY SUB PUMP WITH HOLLOW RODS

One of the main oil production complications is that asphaltene-resin-paraffin deposits (ARPD) are formed during production wells' operation. This is an urgent problem in the oil and gas industry, especially in the fields of the Ural-Volga region (Russia). This study aimed to develop a technological solution for the effective thermal treatment of deposits based on the wells' thermal state calculation during a sucker rod pump operation. In practice, the thermal effect on ARPD is carried out by flushing-out with a hot agent (water, oil). Traditionally, flushes are carried out through the casing annulus. However, this method is ineffective due to large heat losses and the impossibility of heating the inner part of the tubing in a sufficient way, where ARPD is deposited. Dynamic modeling of the process was performed in the ANSYS Fluent software product. The heat problem was solved on the basis of the Navier-Stokes Reynolds-averaged heat and mass transfer equation. It was noted that the temperature of the injected agent (hot oil or water) affects the temperature of the tubing's inner wall to a lesser extent than the coolant flow rate. It has been established that it is impossible to reach the melting point of wax at the submersible pump level. The flow rate of the coolant affects this parameter more intensively. When flushing with hot oil 120°C with a flow rate of 300 m3 /day, the temperature above the pump will be equal to the wax melting temperature. Calculations indicate that it is most advisable to use oil heated to 120°C as a coolant for flushing wells than water with a 90°C temperature. The implementation of the methods proposed can be used on any well equipped with a sucker rod pump.

Assessment of the dust pollution level in the workspaces by the methods of mathematical modeling

Coal dust leakage from coal stacks leads to intensive contamination of the working areas. Therefore, determining level of air pollution near the coal piles for various meteorological situations, when new coal piles are arranged, is an important applied problem. For practice, it is necessary to have quick-calculating mathematical models whiсh take into account the most significant physical processes impacting on formation of contamination zones near the coal piles. Today, to predict the level of air pollution at dust leaking from the coal stacks, the normative technique OND-86 or the Gauss model is used. These forecasting methods make it possible to quickly calculate the contamination zones, but they do not take into account geometric shape of the coal stack and unevenness of the velocity field near it. The subject of this research was creation of a mathematical model for predicting the level of air pollution near coal piles with taking into account the aerodynamics of air flows around them. The purpose of the work was to develop a set of numerical models for quick calculation of the level of air pollution at coal dust leaking from the coal piles with taking into account the uneven emission of dust from different areas of the stack surface. The modelling equations are the three-dimensional mass transfer equation (Marchuk's model) and the three-dimensional equation for the velocity potential. The Marchuk's model allows taking into account rate of the coal dust particles settling, parameters of turbulent diffusion and uneven air flow rate near the coal pile. The Dirac delta function is used for modelling coal dust leaking from various sections of the coal pile. For the numerical solution of the mass transfer equation, a difference splitting scheme is used. On the basis of the three-dimensional equation for the velocity potential, an uneven velocity field near the coal pile is determined. The Richardson method is used for numerical solution of the three-dimensional equation for the velocity potential. An algorithm for solving the problem of calculating a level of contamination of working areas near a coal pile is considered. The description of the structure of the created complex of computer programs is given.

Numerical Simulation on Carbonation Depth of Concrete Structures considering Time- and Temperature-Dependent Carbonation Process

In order to further understand the carbonation process of concrete structures, the time- and temperature-dependent diffusion process of CO2 in concrete is simulated based on the law of the CO2 mass conservation, and a two-dimensional mass transfer equation is established for the CO2 diffusion in concrete. The concrete block is discretized into triangular elements, and the CO2 concentrations at different positions are calculated based on finite element method. A computational algorithm is programed through the Matlab platform. The time- and temperature-dependent property and difference of the CO2 concentration at different positions of the structure are considered in the proposed model. Then, an accelerated carbonation experiment is carried out using concrete blocks with different mix proportions to investigate the influence of the water-cement ratio and temperature on the concrete carbonation. The experimental results effectively verify the correctness of the finite element model, and the proposed finite element method reasonably simulates the concrete carbonation through calculating the carbonation in practical engineering compared with other methods in references. An experimental-numerical correlation has been performed. The ratio of carbonation depth at the corner of the concrete members to the other positions is about 1.35. The carbonation depth is increased about 1.9 times when the temperature changes from 20°C to 40°C.

Pemodelan Transfer Panas dan Massa pada Proses Pengeringan Biji-Bijian Sistem Rak Beserta Solusi Numeriknya

Modeling of heat and mass transfer determine the form of mathematical equations obtained. The aim of this study was to obtain heat and mass transfer equation based on modeling has been prepared and finished using numerical methods. The study starts from determining assumptions, construction of models, make up the mathematical equation of heat and mass transfer, determine the type of numerical methods used, complete the heat and mass transfer equations using numerical methods that have been chosen. Grains as the dried thing modeled as porous bodies. The results shows that the numerical solutions have been successfully made with a series of requirements that must be met to stability.Pemodelan transfer panas dan massa menentukan bentuk persamaan matematis yang diperoleh. Tujuan penelitian ini adalah memperoleh persamaan transfer panas dan massa berdasarkan pemodelan yang telah disusun lalu menyelesaikannya menggunakan metode numerik.Tahapan penelitian dimulai dari menentukan asumsi-asumsi, menyusun model, menyusun persamaan matematis transfer panas dan massa, menentukan jenis metode numerik yang digunakan, menyelesaikan persamaan transfer panas dan massa menggunakan metode numerik yang telah dipilih.Biji-bijian sebagai benda yang dikeringkan dimodelkan sebagai benda porous. hasil penelitian menunjukkan bahwa solusi numerik telah berhasil disusun beserta serangkaian syarat kesetabilan yang harus dipenuhi.