Wyniki wyszukiwania - Biblioteka Nauki

1

Mass transfer enhancement in Newtonian and non-Newtonian liquids flowing in channels of the sinusoidal shape

100%

Broniarz-Press L. , Bednarz J. , Różański J.

International Journal of Applied Mechanics and Engineering

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2005

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tom Vol. 10, no spec

93-98

EN

The aim of the present work was the study of flow phenomena of chosen Stokes fluids in the plate and sinusoidal shape channels of two various types. The first of them had the regular shape and the second one was characterized by the opponent walls displaced in the phase. The constructions of this type can be applied in processing and biotechnology where the media very often have the non-Newtonian character and the laminar flow is required. Mass transfer coefficients in modified channels observed were greater than these ones measured in the plate exchanger. The best effect was obtained for the sinusoidal channel of symmetric construction.

2

Influence of rotating magnetic field on gas-liquid volumetric mass transfer coefficient

100%

Rakoczy R. , Konopacki M. , Kordas M.

Chemical and Process Engineering

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2017

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tom Vol. 38, nr 3

423--432

EN

The main objective of these experiments was to study the oxygen mass transfer rate through the volumetric mass transfer coefficient (kLa) for an experimental set-up equipped with a rotating magnetic field (RMF) generator and various liquids. The experimental results indicated that kLa increased along the magnetic strength and the superficial gas velocity. Mathematical correlations defining the influence of the considered factors on kLa were proposed.

3

Effects of radiation and Eckert number on MHD flow with heat transfer rate near a stagnation point over a non-linear vertical stretching sheet

84%

Fenuga O. J. , Hassan A. R. , Olanrewaju P. O.

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2020

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tom Vol. 25, no. 1

27--36

EN

This work investigates the effects of radiation and Eckert number on an MHD flow with heat transfer rate near a stagnation-point region over a nonlinear vertical stretching sheet. Using a similarity transformation, the governing equations are transformed into a system of ordinary differential equations which are solved numerically using the sixth order Runge-Kutta method with shooting technique. Tabular and graphical results are provided to examine the physical nature of the problem. Heat transfer rate at the surface decreases with radiation, Eckert number and as radiation increases, the flow temperature also increases for velocity ratio parameters […].

4

Review on the numerical investigations of mass transfer from drug eluting stent

84%

Song J. , Kouidri S. , Bakir F.

Biocybernetics and Biomedical Engineering

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2021

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tom Vol. 41, no. 3

1057--1070

EN

Drug-eluting stent (DES) as the newly developed treatment for the cardiovascular disease has been the preferred treatment option for most of the patients with significant reduction of restenosis incidents. However, the follow-up complications such as late thrombosis after stent implantation limit the further widespread use of DES which has caused extensive attention from the researchers. Numerical method has been widely employed to predict the DES performance in human body during the past decades, contributing to the stent design optimization and a better understanding of drug release mechanisms in a cost-effective way compared to the experiments. Among the existing numerical investigations, different modelling methods of DES inside artery can be found to study the drug transport process, and adopting the proper models physically and mathematically plays a key role to obtain the results well fitting with the practical case. Therefore, in this review article, the existing numerical researches regarding DES mainly in the last two decades have been focused and summarized including the established modeling methods and the controlling parameters investigations related to drug release from DES. In addition, the common results obtained have been discussed collectively aiming to guide the following researches.

5

Energetic Efficiency of Mixing and Mass Transfer in Single Phase and Two-Phase Systems

84%

Bałdyga J. , Jasińska M.

Chemical and Process Engineering

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2017

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tom Vol. 38, nr 1

79--96

EN

In this work a concept of energetic efficiency of mixing is presented and discussed; a classical definition of mixing efficiency is modified to include effects of the Schmidt number and the Reynolds number. Generalization to turbulent flows is presented as well. It is shown how the energetic efficiency of mixing as well as efficiencies of drop breakage and mass transfer in twophase liquid-liquid systems can be identified using mathematical models and test chemical reactions. New expressions for analyzing efficiency problem are applied to identify the energetic efficiency of mixing in a stirred tank, a rotor stator mixer and a microreactor. Published experimental data and new results obtained using new systems of test reactions are applied. It has been shown that the efficiency of mixing is small in popular types of reactors and mixers and thus there is some space for improvement.

6

Mathematical analysis of mass and heat transfer through arterial stenosis

67%

Hussain A. , Sarwar L. , Akbar S. , Malik M. Y.

Journal of Power Technologies

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2022

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tom Vol. 102, nr 3

88--95

EN

The article investigates the steady state flow of an incompressible fluid which is treated as a Williamson fluid through a stenoised region in the shape of cosine constriction. Blood is taken as a Williamson fluid. Mathematical formulation leads us to nonlinear compatibility and energy equations, which are then deciphered by the shooting technique to obtain the numerical solution. Suitable resemblance transformations are used to change partial differential equations into an embellished form of ordinary differential equations. Further, the consequences of the different parameters involved are shown by graphs and a conclusion is presented. Velocity and temperature fields are canvassed graphically for the distinct values of emerging parameters and discussed in tabular form. Skin friction and the coefficient of heat transfer are also covered in the discussion. The resulting Nusselt number curve exhibits negative deflection for variational values of λ and height of the stenosis δ.

7

A numerical method for viscous flow in a driven cavity with heat and concentration sources placed on its side wall

59%

Ambethkar V. , Basumatary L. R.

Journal of Applied Mathematics and Computational Mechanics

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2018

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tom Vol. 17, nr 3

17--30

EN

This paper proposes a method to numerically study viscous incompressible two-dimensional steady flow in a driven square cavity with heat and concentration sources placed on its side wall. The method proposed here is based on streamfunction-vorticity (Ψ-ξ) formulation. We have modified this formulation in such a way that it suits to solve the continuity, x and y-momentum, energy and mass transfer equations which are the governing equations of the problem under investigation in this study. No-slip and slip wall boundary conditions for velocity, temperature and concentration are defined on walls of a driven square cavity. In order to numerically compute the streamfunction Ψ, vorticityfunction ξ , temperature θ, concentration C and pressure P at different low, moderate and high Reynolds numbers, a general algorithm was proposed. The sequence of steps involved in this general algorithm are executed in a computer code, developed and run in a C compiler. We propose that, with the help of this code, one can easily compute the numerical solutions of the flow variables such as velocity, pressure, temperature, concentration, streamfunction, vorticityfunction and thereby depict and analyze streamlines, vortex lines, isotherms and isobars, in the driven square cavity for low, moderate and high Reynolds numbers. We have chosen suitable Prandtl and Schmidt numbers that enables us to define the average Nusselt and Sherwood numbers to study the heat ad mass transfer rates from the left wall of the cavity. The stability criterion of the numerical method used for solving the Poisson, vorticity transportation, energy and mass transfer has been given. Based on this criterion, we ought to choose appropriate time and space steps in numerical computations and thereby, we may obtain the desired accurate numerical solutions. The nature of the steady state solutions of the flow variables along the horizontal and vertical lines through the geometric center of the square cavity has been discussed and analyzed. To check the validity of the computer code used and corresponding numerical solutions of the flow variables obtained from this study, we have to compare these with established steady state solutions existing in the literature and they have to be found in good agreement.

8

Modelling of mass transport in watercourses considering mass transfer between phases in unsteady states. Part I. Mass transfer process for periodic and aperiodic changes of concentration

51%

Bielski A.

Environment Protection Engineering

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2011

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tom Vol. 37, nr 2

35-51

EN

A model most often used for the description of the processes of mass transport through phase boundaries is the model of Whitman. Results of calculations obtained using this model may occasionally considerably differ from the results obtained using diffusion models. Thus an attempt has been made to correct the model proposed by Whitman. The dynamics of the processes of mass transport from a liquid phase (river water) to a solid phase (layer of material in the river bottom) has been analysed. Several equations have been derived describing the rate of absorption with a chemical reaction and periodical changes of the concentration of the analysed substance. An attempt has been made to determine the relation between the concentration gradient and concentration at the phase boundary. In dynamic conditions, the concentration gradient at the phase boundary can be approximated by means of time dependence of a linear combination of concentration, delayed concentration, and concentration derivative at the phase boundary. Analysis of the dynamics of the absorption process with the chemical reaction enabled one to derive an equation describing the stream of the substance penetrating to the inside of the solid phase. Such equations may be used to determine the error generated by the film model of Whitman for the process of mass penetration.