scholarly journals NUMERICAL RESEARCH OF THE CHANGE OF REGIME FOR UNSTABLE MASS TRANSFER IN A TERNARY GAS MIXTURE HYDROGEN- NITRIC OXIDE-NITROGEN

2020 ◽  
Vol 72 (4) ◽  
pp. 112-116
Author(s):  
A.B. Kalimov ◽  
◽  
O.V. Fedorenko ◽  
V.N. Kossov ◽  
◽  
...  
Keyword(s):  
Mass Transfer ◽  
Finite Size ◽  
Pressure Change ◽  
Gas Mixture ◽  
Governing Equations ◽  
Diffusion Channel ◽  
Numerical Research ◽  
Pressure Changes ◽  
Matter Transfer ◽  
Good Agreement

On the basis of the software package "MathCad", by solving the Stefan-Maxwell diffusion equations, the evolution of the features of mass transfer in a three-component gas mixture, depending on pressure changes, has been numerically studied. In this analysis, the mixing process is studied in a vertical cylindrical channel of a finite size and at the isothermal conditions. The governing equations are solved at the boundary conditions assuming the absence of matter transfer through the walls of diffusion channel. Through the Rayleigh partial numbers, the influence of the pressure change on the behaviour of diffusion and convective flows is examined. The numerical results reveal that an increase in the pressure leads to a change of modes in ternary gas mixture. The present results are in good agreement with the existing experimental data.

Diffusion and Convective Instability in Ternary Gas Mixture

2013 ◽  
Vol 378 ◽  
pp. 253-258
Author(s):  
Vladimir Kossov ◽  
Yuriy Zhavrin ◽  
Olga Fedorenko
Keyword(s):  
Finite Size ◽  
Gas Mixture ◽  
Governing Equations ◽  
Shadow Method ◽  
Diffusion Channel ◽  
Convective Flows ◽  
Series Of Experiments ◽  
The Stability ◽  
Stability Limits ◽  
Good Agreement

The main objective of this article is to investigate the evolution of the mass transfer regimes in three-component gas mixture subject to the pressure and the diameter of diffusion channel. Two series of experiments on gaseous diffusion instabilities are reported. In one series the stability limits are investigated as a function of pressure and diameter for the system 0.4722 He + 0.5278 Ar - N2. In the other series the convection structures are made visible with the help of shadow method. The experimentalresults reveal that an increase in the pressure and the diameter of diffusion channel leads to a change of the type of mixing in ternary gas mixture.Numerical analysis of the mixing process is studied in a vertical cylindrical channel of a finite size and at the isothermal conditions. The governing equations are solved at the boundary conditions assuming the absence of matter through the walls of diffusion channel. Through the Rayleigh partial numbers, the influences of the pressure and the diameter of diffusion channel on the behaviour of diffusion and convective flows are examined. The present results are in good agreement with the experimental data.

Heat and Mass Transfer during Drying of Clay Ceramic Materials: A Three-Dimensional Analytical Study

2017 ◽  
Vol 10 ◽  
pp. 93-106 ◽  
Author(s):  
M.K. Teixeira de Brito ◽  
D.B. Teixeira de Almeida ◽  
A.G. Barbosa de Lima ◽  
L. Almeida Rocha ◽  
E. Santana de Lima ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Analytical Study ◽  
Separation Of Variables ◽  
Three Dimensional ◽  
Ceramic Materials ◽  
Governing Equations ◽  
Convective Boundary ◽  
Good Agreement

This work aims to study heat and mass transfer in solids with parallelepiped shape with particular reference to drying process. A transient three-dimensional mathematical model based on the Fick ́s and Fourier ́s Laws was developed to predict heat and mass transport in solids considering constant physical properties and convective boundary conditions at the surface of the solid. The analytical solution of the governing equations was obtained using the method of separation of variables. The study was applied in the drying of common ceramic bricks. Predicted results of the heating and drying kinetics and the moisture and temperature distributions inside the material during the process, are compared with experimental data and good agreement was obtained. It has been found that the vertices of the solid dry and heat first. This provokes thermal and hydric stresses inside the material, which may compromise the quality of the product after drying.

Drying (Consolidation) Porous Ceramic by Considering the Microscopic Pore Temperature Gradient

2011 ◽  
Vol 147 ◽  
pp. 210-214 ◽  
Author(s):  
Zawati Harun ◽  
David Gethin
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Porous Ceramic ◽  
Convective Drying ◽  
Comprehensive Model ◽  
Two Dimensional ◽  
Drying Process ◽  
Governing Equations ◽  
Fully Coupled ◽  
Good Agreement

In this work, a two-dimensional numerical model of heat and mass transfer for the convective drying process of ceramic material was developed. The governing equations of fully coupled non-linear partial differential was derived from the most comprehensive model with considering the heat, moisture and gas transport along with the influence of microscopic pore temperature gradient. Through validation the distribution of the measured variables and coefficients (diffusivity) show a good agreement with the drying stage in porous material.

The Response of Pneumatic Transmission Lines to Step Inputs

1959 ◽  
Vol 81 (4) ◽  
pp. 578-583 ◽  
Author(s):  
C. B. Schuder ◽  
R. C. Binder
Keyword(s):  
Fluid Flow ◽  
Distributed System ◽  
Transmission Lines ◽  
Pressure Change ◽  
One Dimensional ◽  
Pressure Time ◽  
Pressure Changes ◽  
Theoretical Results ◽  
Line Following ◽  
Good Agreement

An equation was derived which describes the pressure-time relationship that occurs at the end of a dead-ended or volume-terminated pneumatic transmission line following a sudden pressure change at its input. The two partial differential equations which are solved are basic for transient fluid flow in pipes and analogous to the equations for transient electric current in lines without leakage. The derivation was based on a one-dimensional uniformly distributed system, small, reversible, adiabatic-pressure changes, and laminar flow. Experimental results obtained from tests on 3/8-in. and 1/4-in. tubing showed good agreement with the theoretical results.

The Relation of Isallobaric Wind Components to the Change of Pressure over a Given Locality*

1941 ◽  
Vol 22 (3) ◽  
pp. 117-120
Author(s):  
I. Gringorten
Keyword(s):  
Practical Importance ◽  
Surface Friction ◽  
Pressure Change ◽  
Theoretical Treatment ◽  
Wind Component ◽  
Small Departure ◽  
Gradient Wind ◽  
The Right ◽  
Pressure Changes ◽  
Good Agreement

Non-Technical Summary Why cyclones deepen and fill up is one of the fundamental problems in meteorology that still largely resists theoretical treatment; but it is a matter of great practical importance because it does not seem that our daily forecasts will improve greatly until we find quantitative expressions for the factors leading to development as well as mere translation of pressure systems. Mr. Gringorten in this paper follows up a line of attack already laid down by several European investigators to see how well it may agree with reality. While he does not offer us a new principle the result is very interesting because he shows that the familiar conception of the isallobaric wind component, i.e. the small departure of the wind from the “gradient wind” which follows the isobars (except with surface friction), must play an important role in the pressure changes observed on the weather maps or the barograms every day. Qualitatively we have believed this for some time but Mr. Gringorten has computed the expected pressure change, from formulae proposed by Bjerknes and by Sutcliffe, for a particular time and place. This case was for the layers between 2000 and 8000 feet above Detroit between 7:30 p.m. Feb. 2 and 7:30 p.m. Feb. 3, 1940. The computed pressure change at 2000 feet was at the rate of 22.8 millibars in 12 hours but the observed change was only 5 mb. The practical meteorologist will not regard this as very good agreement but in view of the great difficulties in the theoretical treatment of such a problem the theoretician finds some consolation in that at least the computation gives results in the right direction. Of course, as Mr. Gringorten points out, it was obvious on Feb. 3 from the A. M. weather map that the pressure would fall at Detroit by that evening, and no one would suggest that the theory be used for forecasting.—R. G. S.

Viscous Dissipation and Soret Effects on Non-Darcy Mixed Convective Flow Considering Nanofluids

2013 ◽  
Author(s):  
P. K. Kameswaran ◽  
P. Sibanda ◽  
A. S. N. Murti
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Viscous Dissipation ◽  
Convective Flow ◽  
Volume Fraction ◽  
Dimensionless Temperature ◽  
Governing Equations ◽  
Impermeable Wall ◽  
Mixed Convective Flow ◽  
Good Agreement

We investigate the steady boundary layer mixed convective flow over a horizontal impermeable wall embedded in a porous medium filled with a water-based nanofluid. The model used for the nanofluid incorporates the effects of the volume fraction parameter. The main objective of the present study is to investigate viscous dissipation and Soret effects on heat and mass transfer in a nanofluid containing Al2O3 and TiO2 nanoparticles. The temperature and concentrations at the wall were kept constant. A similarity transformation was used to obtain a system of nonlinear ordinary differential equations. The resulting nonlinear governing equations with associated boundary conditions were solved numerically using the Matlab bvp4c solver. The effects of viscous dissipation and the Soret parameter on dimensionless temperature, concentration, heat and mass transfer are presented graphically. It was observed that the heat transfer rate decreased with an increase in nanoparticle volume fraction. Comparison of current and previously published results (Lai and Kulaki [10], Arfin et al. [12]) showed a good agreement.

Heart Rate Signal Decomposition

2000 ◽  
Vol 39 (02) ◽  
pp. 200-203
Author(s):  
H. Mizuta ◽  
K. Yana
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Pressure Change ◽  
Normal Subjects ◽  
Signal Decomposition ◽  
Large Individual ◽  
Heart Rate Fluctuations ◽  
Type Pattern ◽  
Signal Cancellation ◽  
Pressure Changes

Abstract:This paper proposes a method for decomposing heart rate fluctuations into background, respiratory and blood pressure oriented fluctuations. A signal cancellation scheme using the adaptive RLS algorithm has been introduced for canceling respiration and blood pressure oriented changes in the heart rate fluctuations. The computer simulation confirmed the validity of the proposed method. Then, heart rate fluctuations, instantaneous lung volume and blood pressure changes are simultaneously recorded from eight normal subjects aged 20-24 years. It was shown that after signal decomposition, the power spectrum of the heart rate showed a consistent monotonic 1/fa type pattern. The proposed method enables a clear interpretation of heart rate spectrum removing uncertain large individual variations due to the respiration and blood pressure change.

Unsteady MHD Free Convective Heat and Mass Transfer Flow Past a Vertical Porous Plate in the Presence of Radiation and Chemical Reaction

2017 ◽  
Vol 6 (10) ◽  
pp. 116
Author(s):  
J. Buggaramulu ◽  
M. Venkatakrishna ◽  
Y. Harikrishna
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Chemical Reaction ◽  
Porous Plate ◽  
Physical Parameters ◽  
Governing Equations ◽  
Vertical Porous Plate ◽  
Flow Past ◽  
Transfer Flow

The objective of this paper is to analyze an unsteady MHD free convective heat and mass transfer boundary flow past a semi-infinite vertical porous plate immersed in a porous medium with radiation and chemical reaction. The governing equations of the flow field are solved numerical a two term perturbation method. The effects of the various parameters on the velocity, temperature and concentration profiles are presented graphically and values of skin-frication coefficient, Nusselt number and Sherwood number for various values of physical parameters are presented through tables.

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor

1985 ◽  
Vol 50 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Andreas Zahn ◽  
Lothar Ebner ◽  
Kurt Winkler ◽  
Jan Kratochvíl ◽  
Jindřich Zahradník
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
Horizontal Tube ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Rates ◽  
Type Relation ◽  
Good Agreement

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics. Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.

Sign in / Sign up

Export Citation Format

Share Document