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Journal of Engineering Thermophysics
Journal Prestige (SJR): 0.435
Citation Impact (citeScore): 1
Number of Followers: 4  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1990-5432 - ISSN (Online) 1810-2328
Published by Springer-Verlag Homepage  [2573 journals]
  • Calculation of Radiation Heat Exchange in the Model of Specular-Diffuse
           Reflection and Direct and Diffuse Transmission
    • Abstract: Abstract The general solution to the radiation exchange problem in the zone method is given in the system of surfaces in the presence of nonparticipating medium for the model of specular-diffuse reflection and direct and diffuse transmission. The reflection indicatrix for all surfaces of the considered system of bodies is assumed as a superposition of diffuse and specular components of reflection, and the transmitted radiation for transparent materials—as a superposition of direct and diffuse transmission. The cornerstone of the offered approach is in obtaining the exchange radiation factors by the semi-analytical method by solving a system of linear algebraic equations that include specular exchange factors or diffuse configuration factors of radiation. This allows one to combine exact computational methods of diffuse reflection and diffuse transmission through diffuse configuration factors with methods of direct ray tracing for accounting of specular reflection and direct transmission. Solutions for all possible particular models of reflection and transmission are provided. The solution for diffuse transmission by the semi-analytical method is obtained for the first time. Results of the numerical experiments confirming accuracy and efficiency of the offered approach are given.
      PubDate: 2019-07-01
       
  • Efficiency of Mixture Separation in Distillation Columns with Structured
           Packings under Different Ways of Dynamically Controlled Irrigation
    • Abstract: Abstract The paper presents results of an experimental study of separation efficiency and distribution of flow parameters over the cross section of the distillation columns. The experiments were carried out on the large-scale research setup “Large Freon Column” with diameter of packing of 0.6 m and 0.9 m. The mixture of refrigerants R114 and R21 was used as the working liquid at a pressure of 3 bar in the column. Experimental data were obtained at uniform and nonuniform irrigation of the Mellapak 350.Y and Sulzer 500X structured packings by a controlled liquid distributor. The liquid distributor with independently controlled valves for each drip point was used for controlled packing irrigation. The newmethod for dynamically controlled irrigation of the packing by an operated liquid distributor is suggested. This method is aimed at the destruction of large-scale maldistribution areas (flows) inside the column and the achievement of higher separation efficiency through periodic irrigation of the entire packing or its individual areas under the liquid distributor. The use of dynamically controlled irrigation of the packing allows an increase in efficiency of mixture separation of up to 20%.
      PubDate: 2019-07-01
       
  • Combustion of Substandard Liquid Hydrocarbons in Atmosphere Burners with
           Steam Gasification
    • Abstract: Abstract In this research we experimentally investigated the process of liquid hydrocarbon combustion at spraying by a jet of superheated steam, using waste automobile transmission oil as an example. In the laboratory burner model (up to 20 kW) we studied the effect of mode parameters on the characteristics of the combustion process in the presence of superheated steam, namely, heat release and composition of combustion products, and flame temperature. The possibility of combustion of substandard liquid hydrocarbons in a straight-flow atmospheric burner at 10 kW is shown. Dependences of the main thermotechnical and environmental characteristics of the burner on temperature and flow rate of superheated steam and fuel consumption are found. The fuel combustion efficiency reaches 97%, observing minimal concentrations of toxic combustion products: {CO} = 20 mg/kWh{NO}x = 60 mg/kWh, which corresponds to class 3 of EN 267.
      PubDate: 2019-07-01
       
  • Effect of Internal Heat Generation and Concentration Change on Free
           Convection Boundary Layer from Vertical Flat Plate Embedded in Porous
           Medium
    • Abstract: Abstract The effects of exponentially decaying internal heat generation (IHG) and internal mass generation (IMG) over specific components are presented numerically on coupled heat and mass transfer by a free convection boundary layer over a vertical flat plate embedded in a fluid-saturated porous medium. Corresponding similarity solutions are used to reduce the governing partial nonlinear differential equations to three ordinary differential equations for the dimensionless stream function, temperature, and concentration with the following parameters: buoyancy force N, exponent of x, λ, and Lewis number Le. Media with and without IHG and IMG are compared in context with the help of graphs and tables. Computations are performed with a system of parameters using built-in codes in Maple. The influences of these parameters on velocity, temperature and concentration profiles, and Sherwood and Nusselt numbers are thoroughly compared and graphically illustrated.
      PubDate: 2019-07-01
       
  • Crystallization of Salt Solutions on Surface of Droplet and Layer
    • Abstract: Abstract The evaporation and crystallization of a droplet and a thin layer of aqueous solutions of LiBr and LiCl salts on a heated wall with a temperature Tw = 86°C were studied experimentally. Crystallization curves were obtained for a wide range of initial salt concentrations. For the first time it was shown that for different C01 values the crystallization rates Jcr were different; the Jcr curve was nonlinear. With C01 decreasing, the supersaturation at the onset of crystallization increased, because of different induction times with respect to the generation of the first active crystallization center. It is known for relatively large crystals that heat transfer influences the rate of crystallization. Processing of the experimental data with due account of the basic thermophysical parameters shows that supersaturation also affects the crystal growth. The crystallization rate in a thin layer is significantly higher than in a droplet. It was found that description of crystallization in a droplet should take into account strong anisotropy of the crystallization.
      PubDate: 2019-07-01
       
  • Influence of Joule Heating and Heat Source on Radiative MHD Flow over a
           Stretching Porous Sheet with Power-Law Heat Flux
    • Abstract: Abstract In this paper, a detailed investigation on MHD flow over a porous stretching sheet was conducted by taking power-law heat flux and heat source into account. Series solutions are achieved for the reduced nondimensional ordinary differential equations by admitting an analytical technique known as a homotopy analysis method (HAM). A precise way of convergence of series solutions is also furnished. The attained results of the present study are in excellent connection with the previous results. Nature of magnetic parameter, permeability parameter, radiation parameter, Prandtl number, Eckert number, heat generation parameter and suction/injection parameters on velocity, temperature, skin friction coefficient and Nusselt number are presented in tables and graphs.
      PubDate: 2019-07-01
       
  • Unsteady Slip Flow past an Infinite Vertical Plate with Ramped Plate
           Temperature and Concentration in the Presence of Thermal Radiation and
           Buoyancy
    • Abstract: Abstract Unsteady laminar slip flow along an infinite vertical plate with ramped plate temperature and concentration in the presence of thermal radiation and buoyancy is investigated. Approximated Navier–Stokes equation along with the energy and species equations are solved analytically by adopting the Laplace transform technique. The dependencies of the flow, heat and mass transfer characteristics on time (t), space (y) and nondimensional governing parameters, namely, slip (λ), radiation (R), buoyancy forces ratio (N), Prandtl number (Pr) and Schmidt number (Sc), are explored for both ramped and constant plate temperature and concentration conditions. The results show that radiation effect is appreciable at a lower range of R and found to be greater for the constant than that for the ramped condition. A strong flow near to the plate is generated by radiation and buoyancy effects, and accelerated by slip effect. Finally it is also shown logically and mathematically that in the absence of radiation and presence/absence of slip the flow should be brought to stationary flow when two buoyancies are opposite and equal in magnitude with equal solutal and thermal diffusions.
      PubDate: 2019-07-01
       
  • Mathematical Modeling of Evolution of Swirling Turbulent Jet in Coflowing
           Stream
    • Abstract: Abstract A numerical modeling of a swirling turbulent jet in a coflowing stream was carried out. The flow description involved two second-order mathematical models. The first one includes the averaged equations of motion and the differential equations for transfer of normal Reynolds stresses and dissipation rate in the thin shear layer approximation. The second model relies on the far wake approximation. The distances from the source of the jet in the calculations reached very large values. At small distances, the calculated profiles of the averaged velocity components agree well with the known experimental data from Lavrent’ev Institute of Hydrodynamics SB RAS. At large distances from the source, the flow becomes close to the self-similar one, with degeneration laws and normalized profiles consistent with the known theoretical concepts of the dynamics of swirling turbulent jets in a coflowing stream. The problem of asymptotic behavior of a nonswirling turbulent jet in a coflowing stream was also considered. A self-similar solution based on numerical experiments was obtained.
      PubDate: 2019-07-01
       
  • Mathematical Model of Mass Transfer in Randomly Packed Columns with Phase
           Maldistribution
    • Abstract: Abstract The paper considers the processes of mass transfer between phases in countercurrents of gas and liquid in stationary packed beds of industrial randomly packed column apparatus. Such beds are widely used in heat and mass transfer, separation, and reaction processes in the oil and gas processing, petrochemistry, and other industries. An approximate approach of mathematical modeling of mass transfer in a randomly packed bed at turbulent gas motion and countercurrent laminar wave flow of liquid film is analyzed. The basic concepts of the multispeed continuum model, in which the transfer equations are written for each phase separately, are used. The phases fill one space, the volume of the continuous phase (gas) exceeding by far that of the liquid one. The interaction of the phases is reflected in averaged transfer terms, which take into account the interfacial transfer phenomena. Those are the mass transfer coefficients and the driving forces of the processes. The concentration profiles of the components are found from the solution to differential mass transfer equations written for a cylindrical channel with a volume source of mass. This approach can be used in the absence of experimental data on the structure of gas and liquid flows in a packed bed, for example, when designing new contact elements.
      PubDate: 2019-07-01
       
  • VOF-DPM Simulations of Gas-Liquid-Solid Scrubbing Chambers with Two Gas
           Intake Modes
    • Abstract: Abstract The scrubbing tower plays an important role for gas dedusting in the industry. In this study, the VOF-DPM coupled model is applied to investigate the gas—liquid—solid three-phase flow process in the bottom water chamber of the scrubbing tower. Two gas intake modes of guide-pipe mode and tangential-horn mode are numerically compared. Near the outlet surface, the guide-pipe mode scrubber can obtain lower gas velocity and more uniformly distributed gas phase. This is a good protection for the column tray against being overturned. However, there exists a hydrostatic zone in the guide-pipe mode chamber, this may cause dust to accumulate near the wall. The tangential-horn mode chamber obtains a lower pressure drop and a smaller velocity maximum above liquid level. As a result, to a group of particles range from 50 to 1000 μm, the removal efficiency of the tangential-horn mode scrubber is 88.3%, higher than that of 82.0% of the guide-pipe mode scrubber. The tangential-horn mode performs better in lower pressure drop, higher antiblocking and dust removal ability but worse in protecting the column tray against being overturned. This study offers guidance for the research and design of the wet gas scrubbing chamber.
      PubDate: 2019-07-01
       
  • Flow Pattern of Miscellaneous Liquids with Varied Flow Rates on Structured
           Corrugation SiC Foam Packing
    • Abstract: Abstract Although the unique liquid behavior renders structured corrugation SiC foam packing (SCFP-SiC) a great alternative in distillation, the separation efficiency depends heavily on capacity and liquid property. The aim of this work is to discuss the change of flow pattern with miscellaneous liquids at different flow rates in order to explain the performance of SCFP-SiC in a distillation column. The ultraviolet photography and pulse tracer method were used to estimate the effective flow area and the resident time, respectively. The experimental results indicate that the liquid flow pattern on SCFP-SiC consists of streamflow and transfusion flow. The stream flow can be enlarged by the increase of liquid flow rate so that the effective flow area is reduced, resulting in the decrease of separation efficiency at high liquid capacity. What is more, there exists a vast difference of flow pattern between polar liquid (e.g., water and acetic acid) and nonpolar liquid (e.g., cyclohexane). Transfusion flow of the former is much less than that of the latter, causing the poor performance when separating polar system. Therefore, the liquid capacity and type should be evaluated firstly in the use of SCFP-SiC.
      PubDate: 2019-07-01
       
  • Computational Analysis of Gas Flow in Gas Distributor Breadboard for
           Creating Efficient Devices to Remove Volatile Organic Compounds
    • Abstract: Abstract The paper presents the results of CFD modeling of air flows in a gas distributor breadboard at the inlet of structured catalytic cartridges. The calculation results were used for modifying the gas distributor. Comparison of the experimental and calculated data yielded the most adequate model of turbulence; relationship between the boundary conditions and the accuracy of the modeling results was revealed. Recommendations for improving the distribution of gas flow rates in the selected gas distributor breadboard are formulated.
      PubDate: 2019-07-01
       
  • Aerodynamics Analysis of Several Typical Cars
    • Abstract: Abstract During the process of car movement, the air will cause some resistance to the car, and the resistance will increase rapidly when the speed increases. The aerodynamic characteristics of the car will affect the power, economy, handling stability and comfort during driving. Therefore, reducing the aerodynamic drag of the car is an important prerequisite for improving the overall performance of the car. By using the computational fluid dynamics (CFD) software, the dynamic model of different cars in the process of driving is established and the numerical simulation is carried out to get the distribution diagram of velocity, pressure, resistance, lift, and so on. Through comparison and analysis of different car models, the optimized car is designed to improve the aerodynamic characteristics, and it is of great value in the application of the automotive field.
      PubDate: 2019-04-01
       
  • Heat Transfer and Fouling Rate at Boiling on Superhydrophobic Surface with
           TiO 2 Nanotube-Array Structure
    • Abstract: Abstract A superhydrophobic surface coating of a nanotubes array grown directly on a titanium substrate was prepared by using the method of electrochemical anodic oxidation under ultrasonic assistance and fluoroalkyl silane modification. Experimental investigations of nucleate pool boiling and fouling behaviors were carried out to assess the heat transfer enhancement and fouling inhibition on a superhydrophobic titanium-based nanoporous coating. The superhydrophilic titanium-based nanoporous surface and the bare titanium substrate surface were also investigated as contrasts. The results indicate that the heat transfer performance of the superhydrophobic titanium-based nanoporous coating is superior to the bare titanium substrate and the superhydrophilic titanium-based nanoporous surface due to higher density of nucleation sites in the range of low heat fluxes. Besides, the superhydrophobic nanoporous coating also has lower fouling resistance and better antifouling performance at pool boiling of CaCO3 solution in comparison with bare and superhydrophilic surfaces.
      PubDate: 2019-04-01
       
  • Design and Optimization of Internal Longitudinal Fins of a Tube Using
           Constructal Theory
    • Abstract: Abstract This research is devoted to geometrical optimization of internal longitudinal fins based on constructal theory. These fins are extended inward from the pipe perimeter to a prescribed radius and would have an optimal length, determined analytically by means of constructal theory. The effective parameters of the current study are the ratio of high conductivity to low conductivity, volume fraction of the fins, and the number of the fins. For a round tube with two thermal boundary conditions, i.e., constant heat flux and constant temperature, the optimization length and also the corresponding thickness of fins for a known material ratio are determined parametrically ensuring maximum heat transfer and thermal efficiency In addition, dominancy of conduction heat transfer between fins and convection in the core of pipe are the main assumptions of this research. Finally, our analytical results are verified with their corresponding numerical counterparts.
      PubDate: 2019-04-01
       
  • Analysis of Combustion of Coal-Water Fuel in Low-Power Hot-Water Boiler
           via Numerical Modeling and Experiments
    • Abstract: Abstract The paper presents an experimental and computational study of various regimes of firing coal-water fuel in a low-power hot-water boiler that enable both dry and liquid slag removal. The experimental studies were carried out on a pilot industrial boiler adapted for firing coal-water fuel. The fuel was prepared using flotation products of beneficiation of K grade hard coal. The experiments were accompanied by numerical modeling of combustion processes. The mathematical model includes description of the carrier phase motion (based on the RANS approach with the two-parameter Menter SST k-ω turbulence model), radiation transfer (based on the P1 approximation of the spherical harmonics method for a two-phase two-temperature gray medium), particle motion (based on the Lagrange approach), and gas phase combustion (based on a combination of the kinetic model of combustion of gas components with the vortex break model). The physico-mathematical model was tested on the problem of combustion of coal-water fuel (CWF). One of the goals of the work was verification of a complex mathematical model. A comparative analysis of the results of the numerical modeling and experimental data showed that the model reliably described the process of burning in a combustion chamber. An advanced design of hot-water boiler enabling regimes of both dry and liquid slag removal was investigated. The chamber was shown to provide the necessary conditions for firing CWF in terms of reliability and economy.
      PubDate: 2019-04-01
       
  • Some Aspects of Forced Convection Nanofluid Flow over a Moving Plate in a
           Porous Medium in the Presence of Heat Source/Sink
    • Abstract: Abstract In the present paper heat transfer characteristics for boundary layer forced convective nanofluid flow past a moving plate parallel to a moving stream embedded in a porous medium in the presence of heat source/sink are analyzed. A single-phase fluid model for nanofluid is used. The governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations by means of similarity transformations and then the reduced ordinary differential equations are solved numerically by a shooting technique. The effects of different parameters on velocity, velocity gradient, temperature and temperature gradient for nanofluid with Cu and Ag as nanoparticles are presented and analyzed graphically. For the validation of the numerical scheme, the numerical results obtained in this study are compared with the published data. From the results it is cleared that dual solutions exist when the plate and the free stream move in the opposite directions.
      PubDate: 2019-04-01
       
  • Computational Analysis of Heat and Mass Transfer of Impinging Jet onto
           Different Foods during the Drying Process at Low Reynolds Numbers
    • Abstract: Abstract In the present work, heat and mass transfer from different foods by impinging a slot hot air jet at low Reynolds numbers is numerically researched. Banana and apples are selected as foods due to their trading importance. Low Reynolds numbers are operated as Re = 100, 200 and 300. The diameters of the foods and initial jet height are taken as fixed in all examined situations and the impinging jet is laminar and two-dimensional. The shape of foods is assumed as a cylinder. The distance (D/H) between the cylinder and the slot is taken as another effective parameter of drying process and it is used with the three different distances (D/H = 0.22, 0.25, and 0.33) to search jet effectiveness on heat and mass transfer. A finite volume method is employed to solve governing equations of mass, momentum and energy by means of ANSYS Fluent 17.0 program. There is a good agreement with the numerical and experimental data available in the literature. The heat transfer increments and temperature variations for different Reynolds number values and for varying distance, D/H, and also temperature and mass distributions are researched for both inside the foods. It is obtained that heat and mass transfer enhanced with reducing the distance, D/H, between the jet and the cylinder. In addition, locally, the most effective jet drying is achieved close to the stagnation point on the front face of the foods.
      PubDate: 2019-04-01
       
  • Experimental Study of the Effect of Static Pressure on Turbulent Friction
           Reduction in Gas Saturation of Boundary Layer
    • Abstract: Abstract The article presents the results of an experimental study of the effect of static pressure on reduction of turbulent friction on a plate in gas saturation of the boundary layer. The experiments were carried out on the hydrodynamic stand of the Research Institute of Mechanics of the Moscow State University in the flow rate range U = 4–11 m/s and the static pressure range P = 10–200 kPa, the Reynolds number varied in the range of (3–8)×106. The local friction was measured with a “floating wall” sensor on a strain gage balance, and the gas was blown through a special permeable coating. It was shown that increase in the gas flow rate through a porous wall of flat plate test model could make the reduction of the local friction as high as 80–90%. However, increase in the static pressure in the flow significantly lowered the efficiency of control of the turbulent shear stresses. The friction reduction due to gas saturation of boundary layer depends on the gas flow rate (ceteris paribus) and the static pressure in the flow, which one should take into account when performing integral estimate of the efficiency of the method and assessing the energy loss for gas inlet into the flow.
      PubDate: 2019-04-01
       
  • Parametric Analysis on Water Droplet Dynamics and Phase Change
    • Abstract: Abstract The present paper deepens the analysis on the dynamics and thermal-fluid-dynamics of a sprinkler nozzle-emitted water droplet traveling in air before reaching the ground. The following analysis variables were considered, as main causes of the phenomenon assessed: initial droplet diameter, initial droplet velocity, initial droplet temperature, variable droplet temperature, air temperature, diffusion coefficient of water in air, air relative humidity, inlet droplet throw inclination, thermal radiation, and wind velocity. These variables proved their effect on the droplet travel distance, the droplet time of flight, and the final droplet temperature. The study was carried out thanks to an analytical-numerical model, recently proposed by the same authors of this paper, equipped with a few assumptions that did not alter the realistic description provided. The results proved the effect of each analysis variable and clarify the picture of a complicate yet extremely important phenomenon.
      PubDate: 2019-04-01
       
 
 
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