scholarly journals ESTIMATION OF HETEROGENEITY OF THE ATMOSPHERIC AIR VELOCITY FIELD IN ADSORBERS OF FRONT-END PURIFICATION UNITS FOR AIR SEPARATION PLANTS

2021 ◽  
pp. 117-126
Author(s):  
O.N. Filimonova ◽  
◽  
A.A. Vorobyov ◽  
A.S. Vikulin ◽  
◽  
...  
Keyword(s):  
Mathematical Model ◽  
Velocity Field ◽  
Granular Layer ◽  
Air Separation ◽  
Brinkman Equation ◽  
Turbulent Regime ◽  
Atmospheric Air ◽  
Displacement Mode ◽  
Front End ◽  
Purification Unit

Assuming unidirectional motion of compressed atmospheric air through a vertical cylindrical adsorbent with a fixed granular layer of the front-end purification unit adsorbent, the mathematical model for estimating the heterogeneity of a hydrodynamic velocity field in the radial and axial directions in a turbulent regime is proposed. The model is based on the boundary layer approximation of the Darcy – Brinkman – Forchheimer phenomenological equation. The steady-state flow at low permeability of the granular layer is identified using the collocation method, and the approximate analytical solution is obtained which justifies the applicability of an ideal displacement mode when describing the carrier medium motion. Numerical integration of a boundary value problem of the model equation using the finite-difference method with Richardson extrapolation confirms the conclusion validity. The structure of an accelerated turbulent flow having constant flow velocity in the input section shows that for small Forchheimer coefficients, the Darcy – Brinkman equation is used to obtain the analytical ratio for calculating the length of the initial hydrodynamic section. The proposed mathematical model for estimating the heterogeneity of the velocity field in adsorbers with a stationary dispersed layer is applicable for a laminar flow regime. Testing of this approach by assessing velocity field uniformity for a mass-produced front-end purification unit of air separation plants has shown its efficiency.

scholarly journals Free Interfaces at the Tips of the Cilia in the One-Dimensional Periciliary Layer

Mathematics ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1961
Author(s):  
Kanognudge Wuttanachamsri
Keyword(s):  
Mathematical Model ◽  
Exact Solution ◽  
Free Boundary ◽  
Horizontal Plane ◽  
Numerical Solutions ◽  
Numerical Results ◽  
Brinkman Equation ◽  
Average Height ◽  
Free Interface ◽  
The Mathematical Model

Cilia on the surface of ciliated cells in the respiratory system are organelles that beat forward and backward to generate metachronal waves to propel mucus out of lungs. The layer that contains the cilia, coating the interior epithelial surface of the bronchi and bronchiolesis, is called the periciliary layer (PCL). With fluid nourishment, cilia can move efficiently. The fluid in this region is named the PCL fluid and is considered to be an incompressible, viscous, Newtonian fluid. We propose there to be a free boundary at the tips of cilia underlining a gas phase while the cilia are moving forward. The Brinkman equation on a macroscopic scale, in which bundles of cilia are considered rather than individuals, with the Stefan condition was used in the PCL to determine the velocity of the PCL fluid and the height/shape of the free boundary. Regarding the numerical methods, the boundary immobilization technique was applied to immobilize the moving boundaries using coordinate transformation (working with a fixed domain). A finite element method was employed to discretize the mathematical model and a finite difference approach was applied to the Stefan problem to determine the free interface. In this study, an effective stroke is assumed to start when the cilia make a 140∘ angle to the horizontal plane and the velocitiesof cilia increase until the cilia are perpendicular to the horizontal plane. Then, the velocities of the cilia decrease until the cilia make a 40∘ angle with the horizontal plane. From the numerical results, we can see that although the velocities of the cilia increase and then decrease, the free interface at the tips of the cilia continues increasing for the full forward phase. The numerical results are verified and compared with an exact solution and experimental data from the literature. Regarding the fixed boundary, the numerical results converge to the exact solution. Regarding the free interface, the numerical solutions were compared with the average height of the PCL in non-cystic fibrosis (CF) human tissues and were in excellent agreement. This research also proposes possible values of parameters in the mathematical model in order to determine the free interface. Applications of these fluid flows include animal hair, fibers and filter pads, and rice fields.

CO2 Emission and Energy Assessments of a Novel Pre-Purification Unit for Cryogenic Air Separation Using Supersonic Separator

2019 ◽  
Vol 965 ◽  
pp. 59-67
Author(s):  
George Victor Brigagão ◽  
Lara de Oliveira Arinelli ◽  
José Luiz de Medeiros ◽  
Ofélia de Queiroz Fernandes Araújo
Keyword(s):  
Molecular Sieve ◽  
Low Pressure ◽  
Combined Cycle ◽  
Air Separation ◽  
Total Power ◽  
Trace Species ◽  
Pressure Steam ◽  
Purification Unit ◽  
Air Compression ◽  
Supersonic Separator

Thermal power plants with oxy-combustion CO2 capture are featured by large scale oxygen demand, where cryogenic air separation is most suitable. In such context, a Pre-Purification Unit (PPU) is required, prior to air fractionation, to remove hazardous air contaminants – H2O, CO2 and several trace-species – preventing ingress into the Cold Box. The conventional PPU – named FULL-TSA – remove those contaminants by means of Temperature Swing Adsorption (TSA), ordinarily using double-layered bed with activated alumina for adsorbing H2O and zeolitic molecular sieve for adsorbing CO2 and further trace-species, which implicates in relatively high demand of low-pressure steam for impurities desorption. A novel pre-purification concept (SS-TSA) embraces a Supersonic Separator (SS) performing the bulk of separation service, abating nearly 98.5% of H2O, followed by a finishing single-bed molecular sieve (MS) TSA step, which is featured by its relatively small size, for removing CO2 and remaining impurities. This work presents the energy analysis, as well as the related indirect CO2 emissions, of such a novel concept (SS-TSA) comprising air compression, cooling, SS dehydration and finishing MS-TSA against the conventional method fully based in TSA purification (FULL-TSA). Process simulation in HYSYS 8.8 assisted technical evaluation and comparison of alternatives, which included the use of two Hysys Unit Operation Extensions – SS-UOE and PEC-UOE – for rigorous thermodynamic SS modeling with phase equilibrium sound speed. SS was designed to impose only 1.4% of head loss, while shrinking TSA service to about 10% of FULL-TSA counterpart, also recovering super-cooled aqueous condensate that reduces water make-up and N2 consumption for cooling. Changing from FULL-TSA to SS-TSA the average demand of low-pressure steam reduced from 1.37 to 0.16 MW. In terms of electricity demand the difference was quite small, referring to a tiny increase of 0.07 MW in SS-TSA comparatively to total power demand of 14.97 MW in FULL-TSA. Assuming a natural gas combined cycle cogeneration plant matching requirements to air compression and pre-purification process, equivalent reduction in CO2 indirect emission was 20 kg/h for SS-TSA. These results point superiority of SS-TSA.

scholarly journals Mathematical Model of an Active Front-end voltage rectifier with a Neutral Wire

2020 ◽  
pp. 41-46
Author(s):  
Igor S. Ioffe ◽  
◽  
Anatolii M. Ziuzev ◽  
Aleksey V. Kostylev ◽  
Konstantin E. Nesterov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Front End

Reduction o Air Pollution from Fine Dust by Increasing Efficiency of Gas Emission Purification Sintering Furnaces

2021 ◽  
Vol 25 (12) ◽  
pp. 4-9
Author(s):  
E.V. Kiryushin ◽  
O.V. Pilyaeva ◽  
I.I. Shepelev ◽  
E.N. Eskova
Keyword(s):  
Air Pollution ◽  
Gas Purification ◽  
Fine Dust ◽  
Gas Emission ◽  
Atmospheric Air ◽  
Gas Cleaning ◽  
Waste Gas ◽  
Purification Unit ◽  
High Degree ◽  
Degree Of Purification

The installation of an additional stage of the "wet" waste gas purification unit at the alumina sintering furnaces ensured the achievement of a high degree of purification of gas emissions from fine impurities up to 96 % and the standards of maximum permissible emissions of solid pollutants into the atmosphere established for an industrial enterprise. The formed slude after gas cleaning is proposed to be sent for further processing to the hydrochemistry workshop, thereby ensuring its disposal without contamination of the natural environment. The analysis of air pollution indicators confirmed a decrease in emissions of solid pollutants in the atmospheric air of Achinsk.

HYDRODYNAMIC PROPERTIES AND PERMEABILITY OF FRACTAL OBJECTS

2007 ◽  
Vol 18 (04) ◽  
pp. 732-738 ◽  
Author(s):  
H. NGUYEN ◽  
B. CHOPARD ◽  
S. STOLL
Keyword(s):  
Fractal Dimension ◽  
Velocity Field ◽  
Numerical Simulations ◽  
Lattice Boltzmann ◽  
Hydrodynamic Radius ◽  
Darcy's Law ◽  
Brinkman Equation ◽  
Hydrodynamic Properties ◽  
Fractal Aggregates ◽  
Better Than

Using Lattice Boltzmann numerical simulations, we analyse the hydrodynamic properties of both fractal aggregates and artificial fractal objects. First we show that the hydrodynamic radius actually depends on three quantities: the fractal dimension, the so-called prefactor and the inside connectivity. Second, from the simulated velocity field inside the aggregate, we observe that Darcy's law describes the flow better than Brinkman equation. Finally we measure the permeability - porosity relation and observed that it departs from the prediction of Happel's model.

scholarly journals The Experimental Study of the Kinetics of the Cyclic Adsorption Process of Air Enrichment with Oxygen

2021 ◽  
Vol 27 (3) ◽  
pp. 387-400
Author(s):  
E. I. Akulinin ◽  
D. S. Dvoretsky ◽  
S. I. Dvoretsky
Keyword(s):  
Mass Transfer ◽  
Adsorption Process ◽  
Numerical Study ◽  
Air Separation ◽  
Diffusion Resistance ◽  
Kinetic Regime ◽  
Atmospheric Air ◽  
Mass Conductivity ◽  
Cyclic Adsorption ◽  
Kinetics Of

For mass transfer cyclic processes in the “adsorptive - porous adsorbent” system when air is enriched with oxygen by the method of short-cycle heatless adsorption, a new method has been implemented for determining the coefficients of mass transfer and mass conductivity of processes in systems with a solid phase from kinetic curves. It has been experimentally proved that during the adsorption separation of atmospheric air, the rate of cyclic “adsorption - desorption” processes can be limited by both internal and external diffusion resistance. The mass conductivity coefficients are determined depending on the mass content of the distributed adsorptive (O2, N2) by a method that does not require the implementation of the intradiffusion kinetic regime. The analysis of the kinetics of the process of air enrichment with oxygen is carried out; the coefficients of mass transfer and mass conductivity, which can be used in kinetic calculations and numerical study of the properties and modes of the cyclic adsorption process of atmospheric air separation and oxygen concentration, are determined.

scholarly journals Laboratory model of microwave hyperspectrometer for internal radiation researches of layered natural mediums

2020 ◽  
Vol 97 (1) ◽  
pp. 97-104
Author(s):  
A.V. Ubaychin ◽  
◽  
A.P. Surzhikov ◽  
O. Starý ◽  
A.K. Khassenov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Measurement Errors ◽  
Directional Coupler ◽  
Block Diagram ◽  
Noise Generator ◽  
Laboratory Model ◽  
Internal Radiation ◽  
Front End ◽  
Passive Noise ◽  
The Mathematical Model

This paper describes an achieved result in designing of the four-receiver microwave hyperspectrometer based on zero measurement method and the multi-receiver concept of realization. The block diagrams of the microwave front-end with operating frequency band from 18 to 26.5 GHz, the radiometric receiver, and the frequency transmission module are shown. The technical implementation of every described blocks of the microwave hyperspectrometer are described. Presented technical implementation includes a list of modern components are used to designing of laboratory model of hyperspectrometer. The detailed block diagram of the microwave front-end is presented. Description of main technical characteristics of parts of the microwave front-end is also presented. The analysis of a technical characteristics influence to measurement errors is shown. The mathematical model of a measurement error calculation in hyperspectral modeis described. The influence of the active reference noise generator temperature accuracy, the directional coupler insertion loss and the passive reference noise generator temperature accuracy to a measurement errors are described. A numerical experimental results of designed mathematical model are presented. The dependence of the minimum value of measurement errors form the temperature of passive noise generator is presented.

QUANTUM FIELD APPROACH TO THE THEORY OF DEVELOPED TURBULENCE OF CONDUCTING FERROFLUIDS

1994 ◽  
Vol 08 (17) ◽  
pp. 1027-1040 ◽  
Author(s):  
M. HNATICH ◽  
D. HORVÁTH ◽  
P. KOPANSK
Keyword(s):  
Energy Dissipation ◽  
Velocity Field ◽  
Wide Spectrum ◽  
Turbulent Regime ◽  
Nonlinear Interactions ◽  
Field Approach ◽  
Developed Turbulence ◽  
Physical Problems ◽  
Passive Admixture ◽  
The Magnetic Field

Universality of a principle of the renormalization group (RNG) enables to apply it to a wide spectrum of physical problems, including stochastic problems in the mechanics of continuum. In this paper we study using RNG method statistic properties of a randomly stirred ferrohydrodynamic systems with weak magnetization m. It is shown that also in these systems, similarly to magnetohydrodynamic systems, a steady state asymptotic regime exists in which the spectrum of the pulsation energy has Kolmogorov character k−5/3. In such a regime Lorentz force has no influence on the behavior of a turbulent system on large scales with the result that the magnetic field together with the field of magnetization behave as a passive admixture in the velocity field. It was also shown that strong nonlinear interactions of the velocity field with magnetization generate in the equation for dynamics of the field of magnetization term wν∇2m, which opens a new channel for energy dissipation. Dimensionless "magnetization" Prandtl number w−1 represents the relative intensity of the energy dissipation as compared with other channels and it attains a universal value in the turbulent regime.

A Numerical Study of Thermoacoustic Oscillations in a Rectangular Channel Using CMSIP Method

2009 ◽  
Author(s):  
K. M. Akyuzlu ◽  
K. Albayrak ◽  
C. Karaeren
Keyword(s):  
Mathematical Model ◽  
Velocity Field ◽  
Finite Difference ◽  
Second Order ◽  
Component Model ◽  
Working Fluid ◽  
Two Dimensional ◽  
Throttle Valve ◽  
Heated Channel ◽  
Thermoacoustic Oscillations

This paper presents a mathematical model that was developed to study instabilities (primarily thermoacoustic oscillations) experienced inside a channel (with a rectangular cross section) heated symmetrically (from its top and bottom.) The heated channel is configured to simulate a combustion chamber of a rocket hybrid rocket motor and is connected to a converging–diverging nozzle in the downstream and to a plenum with a flow straightener in the upstream side. The working fluid is supplied from a pressurized storage tank to the upstream plenum through a throttle valve. A multi-component approach is used to model this test apparatus. In this integrated component model, the unsteady flow through the throttle valve and the nozzle is assumed to be one-dimensional and isentropic where as the flow in the forward plenum and the heated channel is assumed to be a two-dimensional, unsteady, compressible, turbulent, and subsonic. The physics based mathematical model of the flow in the channel consists of conservation of mass, momentum (two-dimensional Navier-Stokes) and energy equations subject to appropriate boundary conditions as defined by the physical problem stated above. The working fluid is assumed to be compressible where the density of the fluid is related to the pressure and temperature of the fluid through a simple ideal gas relation. The governing equations are discretized using second order accurate central differencing for spatial derivatives and second order accurate (based on Taylor expansion) finite difference approximations for temporal derivatives. The resulting nonlinear equations are then linearized using Newton’s linearization method. The set of algebraic equations that result from this process are then put into a matrix form and solved using a Coupled Modified Strongly Implicit Procedure (CMSIP) for the unknowns (primitive variables, i.e., pressure, temperature, and the velocity field) of the problem. The turbulence model equations and the unsteady flow equation for the throttle valve are solved using a second order accurate explicit finite difference technique. Convergence and grid independence studies were done to determine the optimum mesh size and computational time increment. Furthermore, two benchmark cases (unsteady driven cavity and laminar channel flows) were simulated using the developed numerical model to verify the accuracy of the proposed solution procedure. Numerical experiments were then carried out to simulate the thermoacoustic oscillations inside rectangular channels with various aspect ratios ranging from 5 to 20 for various operating conditions (i.e., for Re numbers between 102 and 106) and to determine the flow regions where these oscillations are sustained. The numerical simulation results indicate that the mathematical model for the gas flow in the heated channel predicts the expected unsteady temperature and pressure distributions, and the velocity field, successfully. Furthermore, it is concluded that the proposed integrated component model is successful in generating the characteristics of the instabilities associated with thermal, hydrodynamic, and thermoacoustic oscillations in heated channels.

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