Volume 90, №3
EXPERIMENTAL STUDY OF THE CONDITIONS FOR QUENCHING FOREST COMBUSTIBLE MATERIALS
To confi rm the possibility of quenching forest combustible materials by small volumes of water, experimental studies have been made of the processes of interaction of droplets, films, and aerosol flows of water with small sources of combustion of typical forest combustible materials — birch leaves, pine needles, birch and asp twigs. Model combustion sources in the form of cylinders of diameter 20–60 mm and height 40–100 mm were constructed. With the use of high-speed video recording, the characteristic times of thermal decomposition of forest combustibles and the times of suppressing combustion of these materials under various conditions of their interaction with water (pulsed supply of aerosol, injection of water ″mist″ with droplets of radius up to 100 μm, sequential supply of large drops of radius about 1.5 mm) have been determined. Volumes of water suffi cient for suppressing combustion depending on the method of supplying it onto the surface of the reacting forest combustible have been determined. Estimates have been made of the nonreacted portion of the material by comparing the initial mass of the sample of the forest combustible with its final mass (upon quenching the material).
Author: D. V. Antonov, R. S. Volkov, A. O. Zhdanova, G. V. Kuznetsov, and P. A. Strizhak
Keywords: forest combustible material, leaves, needles, twigs, thermal decomposition, quenching, water film, droplet, water ″mist,″ aerosol
PHYSICAL CHARACTERISTICS OF THE EXCITATION AND PROPAGATION OF DETONATION
The problems associated with the history and present-day understanding of the problem of explosions and detonation combustion of gas mixtures are considered
Author: Yu. V. Polezhaev and V. D. Geshele
Keywords: detonation, detonation combustion, gas mixtures
SOLUTION OF TWO-DIMENSIONAL RIEMANN PROBLEMS USING THE METHOD OF PIECEWISE PARABOLIC RECONSTRUCTION
The formulation and solution of two-dimensional gas-dynamics problems associated with the interaction of shock waves, rarefaction waves, and contact discontinuities in the computational domain of simple confi guration are discussed. Results of calculations corresponding to different confi gurations of a two-dimensional Riemann problem are given, and the accuracy of resolution of flow regions with abrupt parametric changes is discussed. The calculation results make it possible to judge the monotonicity and exactness of a numerical solution, the presence of numerical diffusion and phase errors, and also the smoothing of the solution in the regions of its gross change
Author: P. V. Bulat and K. N. Volkov
Keywords: gas dynamics, Riemann problem, difference scheme, shock wave, rarefaction wave, contact discontinuity
ACCURACY OF CALCULATING THE MOMENTUM-LOSS THICKNESS IN A LAMINAR BOUNDARY LAYER ON THE SURFACE OF A HEMISPHERE IN A SUPERSONIC AIR FLOW
An engineering method of calculating the momentum-loss thickness in a laminar boundary layer on the surface of a hemisphere is presented based on the approximation of the results of systematic numerical solutions of boundary layer equations.
Author: V. V. Gorskii, V. A. Sysenko, and K. Yu. Dekermendzhi
Keywords: engineering calculation, heat flux, supersonic flow, laminar boundary layer
CONTROL OF SEPARATING FLOW BEHIND A STEP BY MEANS OF SLOTTED RIBS
One of the promising and simplest methods of passively controlling separating flow behind a backward-facing step with the aid of slotted ribs is considered. The size and number of slots were varied in wide ranges in experiments so that the relative area of the slots amounted to R = Fs/Fr = 0–1. The influence of the longitudinal vortices induced by the teeth in a rib on the distribution of pressure and heat transfer rate in the recirculation region in the case of varying the sizes of slots in a rib, the spacing between them, and the position of the rib relative to the backwardfacing step has been studied. The effectiveness of using slotted ribs for reducing the length and intensity of the region of reverse fl ow behind the step is shown.
Author: A. Yu. D′yachenko, V. L. Zhdanov, Ya. I. Smul′skii, and V. I. Terekhov
Keywords: backward-facing step, separating turbulent fl ow, miniturbulators, thermographic visualization, vortex formation.
DEPENDENCE OF THE MIXING RATE ON PRESSURE IN FREE CONVECTION OF A BINARY MIXTURE OF GASES IN A TWO-FLASK APPARATUS
Consideration has been given to a theoretical model of stationary mixing in free gravitational convection of a binary mixture of gases in a vertical channel with impermeable walls that connects two flasks. It has been shown that with growth in pressure in the supercritical regime the mixing rate peaks, after which it decreases monotonically. A comparison with experimental data has been made and a satisfactory agreement with theoretical results has been obtained.
Author: O. E. Aleksandrov and V. D. Seleznev
Keywords: free convection, binary mixture, vertical channel, mixing rate
TURBULENT NATURAL CONVECTION AND SURFACE RADIATION IN A CLOSED AIR CAVITY WITH A LOCAL ENERGY SOURCE
We have investigated the flow structure and the heat exchange inside a closed square cavity with isothermal vertical and adiabatic horizontal walls in the presence of a local constant-temperature energy source. Analysis has been performed on the basis of solving the equations of mathematical physics describing the considered process in dimensionless variables "stream function–velocity vorticity–temperature." We have obtained the isoline distributions of the stream function and temperature reflecting the influence of the lifting force and the reduced emissivity factor of enclosing surfaces on the flow pattern and the heat transfer. It has been established that an increase in the emissivity of the walls intensifies the convective flow inside the cavity and enhances the heat exchange.
Author: I. V. Miroshnichenko and M. A. Sheremet
Keywords: natural convection, thermal surface radiation, turbulence, diathermal medium, local energy source, finite difference method
CHANGE IN THE AERODYNAMIC CHARACTERISTICS OF AN AEROFOIL AS A RESULT OF THE ONE-SIDED FORCE ACTION OF ITS SURFACE SEGMENT ON THE TRANSONIC FLOW AROUND IT
Mathematical simulation of the forced vibrations of a surface segment on one side of an aerofoil on the shock wave formed in the transonic flow around it has been performed. The influence of the vibrations of this segment in a wide frequency range on the quantitative and qualitative characteristics of the wave drag and lift of the aerofoil were investigated for the case of maximum amplitude of oscillations of the velocity of movement of the vibrating segment of the aerofoil, close to the velocity of the incident flow. It is shown that an additional lifting force arises in this case.
Author: V. P. Zamuraev and A. P. Kalinina
Keywords: transonic flow, aerofoil, forced vibrations, wave drag, lift.
SLIP FLOW AND RADIATIVE HEAT TRANSFER ON A CONVECTIVELY HEATED VERTICAL CYLINDER
An axisymmetric laminar boundary-layer slip flow of a viscous incompressible rarefi ed gas in a convectively heated vertical cylinder in the presence of thermal radiation is analyzed. The governing equations in cylindrical coordinates are transformed into ordinary differential equations by similarity transformation. These transformed equations are then solved numerically, using the fourth order Runge–Kutta method with shooting technique. The effects of the pertinent parameters on the gas velocity, temperature, as well as on the shear stress and heat transfer rate at the cylinder surface, are estimated.
Author: S. Das, R. N. Jana, and O. D. Makinde
Keywords: axisymmetric slip flow, thermal radiation, convective heating, vertical cylinder
ACCOUNT OF INTERFRACTIONAL HEAT TRANSFER IN A HYPERBOLIC MODEL OF A ONE-VELOCITY HETEROGENEOUS MIXTURE
A modifi ed generalized equilibrium model of a one-velocity heterogeneous mixture has been presented in which account is taken of interfractional heat transfer. A characteristic analysis of the model′s equations has been made, and their hyperbolicity has been shown. The Prandtl–Meyer problem and the problem on air–droplet-mixture flow past a wedge has been solved on a curvilinear structured grid using the Godunov method with a linearized Riemannian solver. Results of numerical calculations have been compared with self-similar solutions.
Author: V. S. Surov
Keywords: hyperbolic model of a mixture, interfractional heat transfer, Godunov method, linearized Riemannian solver, Prandtl–Meyer flow
ON THE INTERNAL GAS DYNAMICS AND EFFICIENCY OF A VORTEX WATER-VAPOR PLASMA GENERATOR
Results of experimental investigations of a new-type generator of an arc water plasma, having a high thermal efficiency close to 100%, are presented. This generator represents a system comprising a vortex arc plasma generator, in which an electric arc is stabilized by water vapor and a straight-through-flow tubular electric steam generator. Such a high efficiency of the plasma generator system was achieved due to the refinement of the internal gas dynamics of the plasma generator and the heat and mass transfer in its discharge channel as a result of the improvement of the vortex stabilization and thermal insulation of an arc discharge in it by the specially organized ″instantly permeable″ channel wall cooled by only the working water used for generation of the plasma
Author: L. Charakhovski, A. Essiptchouk, C. Otani, G. Petraconi,. Marquesi, V. Sauchyn, I. Khvedchyn, A. Olenovich, A. Liavonchyk, D. Skamarokhau, and A. Halinouski
Keywords: vortex water-vapor plasma generator, arc plasma, vortex stabilization.
SIMULATION OF THE FILTRATION IN A LOW-PERMEABILITY POOL WITH TWO PERPENDICULAR TECHNOGENIC HYDRAULIC FRACTURES
Results of numerical simulation of the filtration of a fluid in a well with two perpendicular technogenic hydraulic fractures in a low-permeability pool are presented. It was assumed that the filtration in the producing pool and in the fractures adheres to the Darcy law and the permeabilities of the fractures exceed the permeability of the pool by approximately 105 times. Because of the small opening of the fractures, as compared to their length and the distance between them and the boundaries of the pool, the flow of the fluid in the fractures was assumed to be one-dimensional. The influence of the flow capacity and geometry of the primary fracture on the change in the pressure in the well with time was analyzed, and the nonstationary pressure fi elds in the well–fractures–pool system were calculated.
Author: A. Ya. Davletbaev and Z. S. Mukhametova
Keywords: fracture, hydraulic fracturing of a pool, low-permeability pool, well.
FLOWS AND HEAT EXCHANGE IN A GEOTHERMAL BED IN THE PROCESS OF EXTRACTION OF A VAPOR–WATER MIXTURE FROM IT
With the use of the finite-difference method, a nonstationary nonlinear problem on the heat and mass transfer in a geothermal bed in the process of extraction of a vapor–water mixture from it was solved numerically with regard for the heat exchange between the bed and the surrounding rocks. The results obtained were analyzed and compared with the results of earlier investigations. It was established that the heat exchange between the bed and its roof and bottom influences the heat and mass transfer in the neighborhood of a producing well in it. It is shown that this heat exchange increases somewhat the pressure (temperature) of the phase transition of the heat-transfer medium and changes its saturation with water. At the stage of stationary heat and mass transfer in the bed, this change leads to a decrease in the water saturation of the heat-transfer medium, i.e., to an additional evaporation of water from it. However, at the stage of substantially nonstationary heat and mass transfer in the bed, the pattern is more complex: within certain time intervals, the heat exchange in separate regions of the bed decreases the content of vapor in the heat-transfer medium (increases its saturation with water). Moreover, in both the cases of absence and presence of heat exchange between the bed and the surrounding rocks, the distributions of the water saturation of the heattransfer medium in the bed executes damped oscillations and, in so doing, approaches the stationary state.
Author: M. M. Ramazanov, D. A. Alkhasova, and G. M. Abasov
Keywords: geothermal bed, vapor–water mixture, phase transition, heat and mass transfer
PREDICTIVE DETERMINATION OF THE INTEGRAL CHARACTERISTICS OF EVAPORATION OF WATER DROPLETS IN GAS MEDIA WITH A VARYING TEMPERATURE
The possibility of using three heat-transfer models based on ordinary differential equations (ODEs) has been analyzed with account taken of the relevant endothermic phase transformations to predict the integral characteristics of evaporation of liquid droplets (with the example of water) in gas media with a varying temperature. The existing formulations with "diffusive" and "kinetic" approximations to the description of the process of evaporation have been considered, and a new model has been developed according to approximations obtained from the results of conducted experiments (with the use of high-speed cameras and cross-correlation software and hardware systems). Two integral characteristics of the process of evaporation were monitored: the mass rate of vaporization and the lifetime (time of complete evaporation) of a droplet. A comparison of simulation results and experimental data allowed us to draw the conclusion on the expediency of use of ODE-based "diffusive" and "phase-transition" models in a limited temperature range (to 600 K). At high gas temperatures (particularly, higher than 1000 K), a satisfactory correlation with experimental data can be provided by a model that takes account of the substantially nonlinear dependence of the vaporization rate on temperature, the formation of a buffer (steam) layer between the droplet and the gas medium, and the basic mechanisms of heat transfer in the liquid and in the gas medium.
Author: O. V. Vysokomornaya, G. V. Kuznetsov, and P. A. Strizhak
Keywords: droplet, water, high-temperature gases, heat transfer, evaporation, vaporization rate, lifetime, simulation
EXPERIMENTAL DETERMINATION OF CONDITIONS FOR THE EXPLOSIVE FRAGMENTATION OF A HETEROGENEOUS WATER DROPLET IN HEATING IN A HIGH-TEMPERATURE GAS MEDIUM
An experimental study has been made of the processes of warming up, evaporation, and boiling of a heterogeneous (with a solid graphite particle) droplet of water in a flow of high-temperature (500–800 K) combustion products. The mechanism of explosive fragmentation (breakup) of the heterogeneous droplet with enhancement of vaporization on internal interfaces (during the nucleation of vapour bubbles at the graphite-particle surface) has been established. The characteristic times of heating of the heterogeneous droplet (2.5–4 mm in size) with an inclusion (in the shape of a cylindrical disk of diameter and height 2 mm) to explosive-fragmentation conditions have been determined. The times of complete evaporation of a liquid fi lm from the inclusion during the implementation of the process of vaporization from the free exterior surface of the droplet have also been given. A signifi cant difference of the conditions and characteristics of the investigated processes from the "graphite substrate–water droplet" system has been shown. Conditions under which the controlling share of heat to internal interfaces of the heterogeneous droplet is supplied through the liquid fi lm or the inclusion have been determined.
Author: G. V. Kuznetsov, M. V. Piskunov, and P. A. Strizhak
Keywords: high-temperature gases, solid inclusion, heterogeneous droplet of a liquid, explosive fragmentation, evaporation, boiling
SATURATED VAPOR PRESSURE OF HYDROGEN FLUORIDE IN THE REGION OF LOW TEMPERATURES
The results of measuring the saturated vapor pressure of anhydrous hydrogen fluoride in the temperature interval 140–190 K are presented. The schematic diagram of a testrig, instrumentation, and the technique of measurements are described.
Author: S. M. Gubanov, M. I. Durnovtsev, and A. Yu. Krainov
Keywords: hydrogen fluoride, saturated vapor pressure, experimental measurements
NUMERICAL SIMULATION OF FILM COOLING WITH A COOLANT SUPPLIED THROUGH HOLES IN A TRENCH
The results of numerical simulation and experimental investigation of the effi ciency of fi lm cooling behind a row of holes in a trench in the range of blowing ratio variation 0.5 ≤ m ≤ 2.0 are presented. This scheme is of practical interest for use in the systems of cooling the blades of high-temperature gas turbines. Comparative analysis has shown that the effi ciency of the trench scheme substantially exceeds the effi ciency of the traditional scheme. The commercial package ANSYS CFX 14 was used in the Calculation Fluid Dynamics (CFD) modeling of film cooling. It is shown that the best agreement between predicted and experimental data is provided by the use of the SST model of turbulence. Analysis of the physical picture of flow has shown that the higher efficiency of film cooling with secondary air supply to the trench is mainly due to the preliminary spreading of a coolant in the trench, decrease in the intensity and scale of the vortex pair structure, absence of the coolant film departure from the plate surface, and to the more uniform transverse distribution of the coolant film
Author: A. A. Khalatov, N. A. Panchenko, I. I. Borisov, and V. V. Severina
Keywords: film cooling, efficiency, holes in the trench, numerical simulation
MATHEMATICAL MODELS AND CALCULATION OF THE COEFFICIENTS OF HEAT AND MASS TRANSFER IN THE PACKINGS OF MECHANICAL-DRAFT TOWERS
Semiempirical expressions for calculating the average coefficients of heat and mass transfer in the blocks of fi lm-type sprayers are considered. The equations of the Chilton–Colburn hydrodynamic analogy, Prandtl model, generalizations of the hydrodynamic analogy, as well as dimensionless expressions and experimental data of various authors have been used. It is shown that the best agreement with experiment is provided by equations obtained with the aid of the hydrodynamic analogy and Prandtl model
Author: A. G. Laptev and E. A. Lapteva
Keywords: heat and mass transfer, fi lm fl ow, cooling tower, analogy, boundary layer, packings
DETERMINATION OF THE HEAT AND MASS TRANSFER EFFICIENCY AT THE CONTACT STAGE OF A JET-FILM FACILITY
A contact jet-film facility has been developed for increasing the effi ciency of operation of industrial cooling towers. The results of experimental and analytical investigation of the operation of this facility, its hydraulic resistance, and of the heat and mass transfer effi ciency of its contact stage are presented.
Author: O. S. Dmitrieva, I. N. Madyshev, and A. V. Dmitriev
Keywords: heat and mass transfer, contact jet-fi lm facility, cooling system
CALCULATION OF THE THERMAL LOADING OF THE CYLINDER-PISTON GROUP OF THE AUTOMOBILE ENGINE
We propose a mathematical model for calculating thermal loods of parts of the cylinder-piston group of the automobile engine operating under unstable conditions in its complete life cycle. Methods have been described for calculating the boundary conditions to determine the thermal state of the parts of the cylinder-piston group of such an engine with the use of theoretical formulas, empirical and semiempirical relations, and tabulated data. In modeling, we calculated the work of all systems of the engine (pumps, pipelines, heat exchangers) influencing directly or indirectly the thermal state of its cylinder-piston group. The nonstationary thermal state was calculated once in the operating cycle of the engine with the use of the cycle-averaged values of the local heat transfer coeffi cients and the resulting temperature of the medium. The personal computer counting time for one time step of a transport diesel engine of typical design with a number of units of the order of 500 was 5 s.
Author: F. B. Barchenko and V. N. Bakulin
Keywords: automobile engine, cylinder-piston group, thermal loading.
EXPERIMENTAL STUDY OF THE KINETICS OF DRYING OF THIN PLANE MOIST MATERIALS BY THE REGULAR-REGIME METHOD USING GENERALIZED COMPLEX VARIABLES
Results of experimental study of the kinetics of drying of thin materials have been presented. Fundamental experimental equations to calculate the kinetic parameters of the process of drying, i.e., the heat-flux density, the integral mean temperature, and the duration of drying, have been given.
Author: A. I. Ol′shanskii and A. M. Gusarov
Keywords: moisture content, integral mean temperature, rate of heating, rate of decrease in the moisture content
INFLUENCE OF IMPERFECTIONS OF RADIATION AND TECHNOLOGY ON THE THERMALLY DEFORMED STATE OF OPTICAL ELEMENTS
The authors have performed calculation and an analysis of the thermally stressed state of optical elements (mirror, passage windows, and beam splitters). A study has been made of the temperature fi elds, stresses, bending thermal displacements, and expansions of the optical surface of these elements under inhomogeneous local conditions of their loading depending on the defects existing in them.
Author: Yu. I. Shanin, O. I. Shanin, A. V. Chernykh, and I. S. Sharapova
Keywords: thermal deformation, heat fl ux, cooling system, optical element, laser mirror
THERMOPHYSICAL PROPERTIES AND TEMPERATURE OF THE START OF TITANIUM RECRYSTALLIZATION IN DIFFERENT STRUCTURAL STATES
The results of measurements of the thermal diffusivity, thermal conductivity, and heat capacity of VT1-0-grade titanium samples in as-cast, deformed submicrocrystalline, and sintered states are presented. It has been established that the decrease in the thermal conductivity and thermal diffusivity of titanium in the submicrocrystalline and sintered states is associated with the increase in the quantity of defects in the material volume, whereas the increase in the temperature of polymorphic transformation of titanium is connected with the dissolution of oxygen in its lattice. The results of investigation of the coefficient of thermal linear expansion of titanium in the macrocrystalline and submicrocrystalline states are presented. The decrease in the coefficient of thermal linear expansion of titanium of submicrocrystalline structure has been established, which may point to the decrease in its melting temperature. It is shown that annealing of samples in a submicrocrystalline state leads to the growth of the temperature coefficient of linear expansion, bringing its value closer to the temperature coeffi cient of linear expansion of titanium in the equilibrium state. Studies by the method of back reflection photography in a KROS chamber made it possible to estimate the temperature of the start of VT1-0-grade titanium recrystallization after intense plastic deformation by the twist extrusion method. The decrease in the temperature of the start of recrystallization for titanium in the deformed submicrocrystalline state has been established. Based on the trends revealed, optimum regimes of thermal treatment of VT1-0-grade titanium for removing internal stresses and preserving the submicrocrystalline structure have been established.
Author: D. V. Pavlenko, D. V. Tkach, S. M. Danilova-Tret′yak, and L. E. Evseeva
Keywords: titanium, twist extrusion, structural state, thermophysical properties, thermal conductivity, thermal coeffi cient of linear expansion, recrystallization temperature
IMPLEMENTATION OF NONDESTRUCTIVE TESTING OF MASSIVE PRODUCTS IN MEASURING THE DIFFUSIVITY OF SOLVENTS
Consideration is given to the problem of determination of the range of variation of the regime parameters of the process of measuring the diffusivity of solvents in massive products manufactured from capillary-porous materials with the aim of improving the effi ciency and accuracy of the employed nondestructive-testing method. The order of implementation of measurement operations of the developed method is determined as a result of the performed investigations. The accuracy in determining the sought diffusivity is improved due to the concentration maximum of the solvent falling within the rational range of the static characteristics of a galvanic sensor used to monitor the local concentration of solvents. Reduction in the expenditure of time and funds is ensured by eliminating the need for individual calibration of the measure of concentration of solvents of the analyzed materials in a solid phase for each new system ″capillary-porous material–solvent,″ and also for numerous trial experiments with different volumes of a pulsed-action dose to improve the accuracy of the method.
Author: V. P. Belyaev, S. V. Mishchenko, and P. S. Belyaev
Keywords: capillary-porous material, diffusivity of solvents, nondestructive testing
STRENGTH AND STIFFNESS ANALYSIS BY THE FINITE-DIFFERENCE METHOD OF A CONCRETE FLOOR SLAB REINFORCED WITH COMPOSITE RODS DURING A FIRE
A strength and stiffness comparative analysis has been made of a concrete slab reinforced with compositereinforcement rods and a slab reinforced with steel rods. The stress-strain state has been assessed for both versions of reinforcement of the slab. The stress-strain state was determined under the action of only static load and with subsequent application of temperature fields, i.e., under standard-fi re conditions. It has been shown that the fire resistance of the slab with a composite reinforcement turns out to be 1.6 higher as far as the bearing capacity is concerned, than the fire resistance of the slab with a steel reinforcement, although the initial defl ection due to the action of only static load for the slab reinforced with composite rods exceeds six to seven times the deflеction of the slab reinforced with steel rods.
Author: A. V. Shirko, A. N. Kamlyuk, A. S. Drobysh, and A. V. Spiglazov
Keywords: strength, loading, fi nite-element method, concrete, composite and steel reinforcements, temperature fi elds, stress, fi re resistance
RIGIDITY OF THE BEARING ELEMENTS OF THE CONTACT STRUCTURES OF A MASS-TRANSFER APPARATUS
A contact structure for intensifi cation of heat and mass transfer processes at small expenditures of energy has been developed. The possible deformations of a contact structure in the process of operation have been estimated with the aid of a mathematical model. To determine the rigidity of the rods supporting the structure, a computer program has been developed that made it possible to locate the model defl ections at the points of interest. The results of calculations of the rigidity of the bearing members of the developed contact structures are presented.
Author: A. V. Dmitriev,a I. A. Sabanaev,b and O. S. Dmitrieva
Keywords: mass transfer, contact structures, energy saving, rigidity
ON SETTING A BOUNDARY CONDITION FOR THE EQUATION OF CONVECTIVE DIFFUSION OF HYDROGEN IN A LIQUID METAL UNDER THE ACTION OF AN ELECTROSTATIC FIELD
The Sieverts relation is generalized to the case of setting a boundary condition for the equation of convective diffusion of hydrogen in a liquid metal by supplementing it with the electric field strength and the degree of ionization of hydrogen atoms in a melt. The relation obtained agrees qualitatively with the results of laboratory investigations. It can be used in computer simulation of convective diffusion of hydrogen in a liquid metal subjected to the action of external electrostatic field.
Author: I. I. Zakharov
Keywords: boundary condition, convective diffusion, liquid metal, electrostatic fi eld
EFFECT OF CHARGED CLUSTERS ON THE DIFFUSION OF IMPURITY ATOMS IN SILICON CRYSTALS
An equation of diffusion of impurity atoms in silicon crystals has been obtained, based on which the influence of charged clusters in a silicon crystal on the process of impurity transfer can be determined. It is shown that a characteristic feature of this effect is the appearance of an additional flux of impurity atoms, which is capable of leading to impurity segregation
Author: O. I. Velichko
Keywords: diffusion, segregation, cluster, impurity, silicon
EFFECTIVENESS OF OPERATION OF ORGANIC RANKINE CYCLE INSTALLATION APPLIED IN THE LIQUID NATURAL GAS REGASIFICATION PLANT
An analysis of the operation of an Organic Rankine Cycle (ORC) installation heated by a low-temperature heat source is presented for the case where a condenser of a working fluid is cooled by a liquid of ultralow temperature. For this purpose, the process of regasifi cation of liquid natural gas (LNG) is considered. In the process, the condensation heat of the working fluid in ORC is taken by the LNG evaporating subsequently (i.e., undergoing regasifi cation). The paper presents the schematic of this installation and its application, as well as the results of calculations on the basis of the analysis in terms of the power and effi ciency. In the analysis, organic fluids used in the ORC as working ones have been selected
Author: R. Kaczmarek and A. A. Stachel
Keywords: ORC power plant, LNG, LNG regasification plant
SHOCK WAVES IN INERT AND REACTIVE MEDIA
Shock waves are of special interest from a whole number of aspects. On the one hand, where attempts at integrating equations without introducing discontinuities (i.e., shock waves) lead to these or those paradoxes and to the impossibility of solving these equations, the shock wave theory resolves paradoxes and permits creating regimes of motion under any conditions. One the other hand, shock waves themselves are a paradoxical event. They are paradoxical in the sense that without making any assumptions about dissipative forces — about viscosity and heat conduction — we obtain, from elementary considerations, laws, according to which there is an increase in entropy, i.e., laws, according to which the processes proceeding in the shock wave are irreversible.″
Author: N. A. Fomin
Keywords: shock wave, combustion, detonation, supersonic flows