scholarly journals Onset of Linear and Nonlinear Thermosolutal Convection with Soret and Dufour Effects in a Porous Collector under a Uniform Magnetic Field

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 243
Author(s):  
Redha Rebhi ◽  
Mahmoud Mamou ◽  
Noureddine Hadidi
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Thermosolutal Convection ◽  
Soret And Dufour Effects ◽  
Onset Of Convection ◽  
Electrically Conducting ◽  
Dufour Number

The present paper reports on an analytical and numerical study of combined Soret and Dufour effects on thermosolutal convection in a horizontal porous cavity saturated with an electrically conducting binary fluid under a magnetic field. The horizontal walls of the system are subject to vertical uniform fluxes of heat and mass, whereas the vertical walls are assumed to be adiabatic and impermeable. The main governing parameters of the problem are the Rayleigh, the Hartmann, the Soret, the Dufour and the Lewis numbers, the buoyancy ratio, the enclosure aspect ratio, and the normalized porosity of the porous medium. An asymptotic parallel flow approximation is applied to determine the onset of subcritical nonlinear convection. In addition, a linear stability analysis is performed to predict explicitly the thresholds for the onset of stationary, overstable and oscillatory convection, and the Hopf bifurcation as functions of the governing parameters. The combined effect of a magnetic field, Soret and Dufour parameters have a noticeable influence on the intensity of the convective flow, the heat and mass transfer rates, and the thresholds of linear convection. It is found that the imposition of a magnetic field delays the onset of convection and its intensification can lead to the total suppression of the convective currents. The heat transfer rate increases with the Dufour number and decreases with the Soret number and vice versa for the mass transfer rate.

Influence of Induced Magnetic Field and Radiation on Free Convective Jeffrey Fluid Flow between two Parallel Porous Plates with Soret and Dufour Effects

2019 ◽  
Vol 35 (5) ◽  
pp. 657-675 ◽  
Author(s):  
Odelu Ojjela ◽  
Adigoppula Raju ◽  
N. Naresh Kumar
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Differential Equations ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Deborah Number ◽  
Jeffrey Fluid ◽  
Parallel Plates ◽  
Induced Magnetic Field ◽  
Soret And Dufour Effects

ABSTRACTThe present article deals with the influence of the induced magnetic field on an unsteady two dimensional incompressible free convective chemically reacting slip flow of Jeffrey fluid between two parallel plates under the influence of the thermal radiation, Soret and Dufour. It is assumed that the flow is generated due to periodic suction/injection and the non-uniform temperature and concentrations are varying periodically with time at the plates. The governing partial differential equations are reduced into nonlinear ordinary differential equations by using similarity transformations and solved by shooting method along with Rung-Kutta 4th order scheme. The results are analyzed for various flows, heat and mass transfer characteristics with respect to various prominent parameters such as the ratio of relaxation to retardation times, Deborah number, magnetic Reynold’s number, Strommer’s number, radiation parameter, chemical reaction parameter, Soret and Dufour numbers in details through graphs and tables. It is observed that the temperature of the fluid is enhanced with Soret and Dufour whereas the concentration is decreased. Also the mass transfer rate of the fluid is enhanced with Strommer’s number, whereas the heat transfer rate decreases with increasing of the Jeffery fluid parameter. The present results have good agreement with published work for Newtonian case.

scholarly journals Numerical Study of Natural Convective Heat and Mass Transfer in an Inclined Porous Media

2018 ◽  
Vol 8 (4) ◽  
pp. 3223-3227
Author(s):  
A. Latreche ◽  
M. Djezzar
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Coupled Equations ◽  
Dimensional Parameters ◽  
Finite Volume Approach

In this study, two dimensional natural convection heat and mass transfer generated in an inclined rectangular porous cavity filled with Newtonian fluid has been investigated numerically. The cavity is heated and cooled along horizontal walls while the solutal gradient is imposed horizontally. The physical model for the momentum conservation equation makes use of the Darcy model, and the set of coupled equations is solved using a finite volume approach. The successive-under-relaxation (SUR) method is used in the solution of the stream function equation. The results are presented graphically in terms of streamlines, isotherms and iso-concentrations. The heat and mass transfer rate in the cavity is measured in terms of the average Nusselt and Sherwood numbers for various non-dimensional parameters.

Mass Transfer Rate Enhancement in Sparged Vessel for Ammonia-Water Nano-Fluid in VARS by Adding Nanoparticles

2020 ◽  
Author(s):  
Rahul Bhujbal ◽  
Sanjay Nakate ◽  
Sunil V. Dingare
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Solution Flow Rate ◽  
Low Grade ◽  
Efficient Design ◽  
Operation Condition ◽  
Solution Flow ◽  
Ammonia Water

Abstract The refrigeration systems are used in domestic and commercial freezing applications. These systems are needed to be used energy efficiently to get the economic operation condition. The vapor compression refrigeration cycle (VCR) is getting replaced by vapor absorption refrigeration system (VARS) as they can use low grade energy. This VARS can be used by making use of waste energy in the form of heat which is readily available for many applications. Performance of the VARS is dependent on the generator and absorber performance. In absorber it is based on the amount of refrigerant absorbed and the solution flow rate. Experimental and Numerical study of bubble absorber and effect of nanoparticle on ammonia water mass transfer is carried out. In this study, different designs for the absorber chamber are viewed and compared together, based on the research did earlier. Looking at the aspects of bubble type absorber designs, these designs give better mass transfer performance as compared to other designs. These designs may be improved to get the energy efficient design of the absorber. Present study includes the enhancement of mass transfer rate by the addition of nanoparticles using aluminum oxide (Al2O3). Here, sparged vessels with NH3-H2O binary fluid are arranged with varying percentage of nanoparticle (Al2O3). This study includes the study of mass transfer enhancements by using nanoparticles. Based on the experimental results carried out for the varying mass flow rates it is found that the mass transfer rate is enhanced significantly, it is because the interfacial area is enhanced by the addition of nanoparticles to the base fluids.

Numerical Study on Boiling Mechanism and Rapid Phase Transfer Phenomenon of LNG Discharging on Water

2012 ◽  
Vol 516-517 ◽  
pp. 97-106 ◽  
Author(s):  
Bin Zhang ◽  
Wan Qing Wu ◽  
Jian Wei Zhang
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Water Surface ◽  
Phase Transfer ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Initial Time ◽  
Rapid Phase ◽  
Boiling Mechanism ◽  
Superheat Limit

Abstract. Aiming at analyzing boiling mechanism and confirming rapid phase Abstract. Aiming at analyzing boiling mechanism and confirming rapid phase transfer (RPT) taking place conditions of LNG discharging on water. The models of pool spreading, heat and mass transfer rate and LNG’s property are coupled in this paper. The conditions of RPT has been confirmed, which included LNG directly contacting with water and the water temperature should higher than LNG’s superheat limit temperature, but the RPT would not take place if the LNG boils on ice. The model of LNG discharging on water has been established in this paper, which is used to simulate Boe and Burro-9 experiments. The results showed that the models can simulate evaporation and boiling rate well, and can be used in predicting the initial time of RPT happening when the discharging process is calm and the location of discharging is near the water surface.

scholarly journals Boundary Layer Flow, Heat and Mass Transfer of Cu-Water Nanofluid over a Moving Plate with Soret and Dufour Effects: Stability Analysis

2021 ◽  
Vol 82 (1) ◽  
pp. 96-104
Author(s):  
Najwa Najib ◽  
Norfifah Bachok
Keyword(s):  
Mass Transfer ◽  
Differential Equations ◽  
Heat And Mass Transfer ◽  
Transfer Rate ◽  
Soret Effect ◽  
Mass Transfer Rate ◽  
Moving Plate ◽  
Soret And Dufour Effects ◽  
Layer Flow ◽  
The Stability

Our main focus in this paper is to investigate the effects of Soret and Dufour known as thermodiffusion and diffusion-thermo on moving plate in copper water nanofluid. The set of partial differential equations are converted into set of ordinary differential equations using the appropriate similarity variables before being solved numerically using bvp4c code in Matlab software. The results of heat and mass transfer, temperature and concentration profiles on Soret as well as Dufour effects are presented graphically. Soret effect increases the heat transfer rate at the surface while Dufour effect decreases the mass transfer rate at the surface. Since the solutions exist in dual, we carry out the stability solutions to determine which solution is stable and hence the physical meaning is realized physically.

Slip Flow of an Unsteady Nanofluid Past a Stretching Surface in a Transverse Magnetic Field Using SRM

2018 ◽  
Vol 387 ◽  
pp. 562-574 ◽  
Author(s):  
K. Gangadhar ◽  
K.V. Ramana ◽  
S. Mohammed Ibrahim ◽  
Oluwole Daniel Makinde
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Transverse Magnetic Field ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Slip Flow ◽  
Transverse Magnetic ◽  
Problem Solver ◽  
Surface Shear Stress ◽  
Stretching Surface

A theoretical and numerical examination has been completed to talk about the unsteady, two dimensional slip flow of a nanofluid of heat and mass transfer with transverse magnetic field was investigated in this paper. A stretching surface is used to investigate the flow. Obtained nonlinear equations are solved by Spectral Relaxation Method (SRM) technique and the results are verified by comparing the results obtained by using the Matlab in-built boundary value problem solver bvp4c, and the outcomes which are published in previous papers. The outcomes are exhibited pictorially and talked about difference coming about parameters. Expanding heat transfer rate, mass transfer rate and velocity slip raises velocity yet to be diminishes temperature and skin friction (surface shear stress).

Numerical Study on the Characteristics of Natural Supercavitation by Planar Symmetric Cavitators With Streamlined Headforms

2017 ◽  
Author(s):  
Zhi-Ying Zheng ◽  
Lu Wang ◽  
Qian Li ◽  
Yue Wang ◽  
Wei-Hua Cai ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Liquid Phase ◽  
Vapor Phase ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Three Dimensional ◽  
Pressure Drag ◽  
Hyperbolic Cosine ◽  
Blade Shape

A novel supercavitation-based device named Rotational Supercavitating Evaporator (RSCE) was recently designed for desalination. In order to improve the blade shape of rotational cavitator in RSCE for performance optimization and then design three-dimensional blades, two-dimensional numerical simulations are conducted on the supercavitating flows (with cavitation number ranging from 0.055 to 0.315) around six planar symmetric cavitators with different streamlined headforms utilizing k – ε – v′2 – f turbulence model and Schnerr-Sauer cavitation model. We obtain the characteristics of natural supercavitation for each cavitator, including the shape and resistance characteristics and the mass transfer rate from liquid phase to vapor phase. The effects of the shape of the headform on these characteristics are analyzed. The results show that the supercavity sizes for most cavitators with streamlined headforms are smaller than that for wedge-shaped cavitator, except for the one with the profile of the forebody concaving to the inside of the cavitator. Cavitation initially occurs on the surface of the forebody for the cavitators with small curvature of the front end. Even though the pressure drag of the cavitator with streamlined headform is dramatically reduced compared with that of wedge-shaped cavitator, the pressure drag still accounts for most of the total drag. Both the drag and the mass transfer rate from liquid phase to vapor phase are in positive correlation with the supercavity size, indicating that the cavitators with the elliptic and hyperbolic cosine-type forebodies could be utilized for the optimal design of three-dimensional blade shape of RSCE.

Numerical study on gas–liquid two-phase flow and mass transfer in a microchannel

2021 ◽  
Vol 19 (3) ◽  
pp. 295-308
Author(s):  
Jin Zunlong ◽  
Liu Yonghao ◽  
Dong Rui ◽  
Wang Dingbiao ◽  
Chen Xiaotang
Keyword(s):  
Mass Transfer ◽  
Surface Tension ◽  
Slug Flow ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Plug

Abstract A numerical study of the gas–liquid two-phase flow and mass transfer in a square microchannel with a T-junction is carried out in this work. Through numerical simulation methods, the flow patterns of bubble flow, slug flow and annular flow are determined. By proposing a new flow pattern conversion relationship with different media and different speeds, 100 sets of CO2-water flow patterns and 100 sets of CO2-ethanol flow patterns are obtained. The effects of surface tension on flow pattern, bubble length and liquid plug length are studied. The pressure distribution and pressure drop are analyzed, and mass transfer is obtained through slug flow simulation, and the influencing factors of gas–liquid mass transfer are studied. The results show that the effect of surface tension on the length of the bubble and the length of the liquid plug is completely opposite, the pressure distribution is stepped, and the pressure drop increases with the increase of the gas–liquid velocity. In addition, it was found that the volumetric mass transfer coefficients of the bubble cap and the liquid film gradually decreased with time, and eventually stabilized. The increase in bubble velocity accelerates the mass transfer rate, while the increase in unit cell length slows the mass transfer rate. However, the influence of film thickness and liquid film length on mass transfer varies with time.

Numerical Investigation on the Effect of Tube Geometry and Feeder Height on the Heat Transfer Performance of Horizontal Tube Falling Film Evaporation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
D. Balaji ◽  
R. Velraj ◽  
M. V. Ramana Murthy
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Film Thickness ◽  
Transfer Rate ◽  
Numerical Study ◽  
Mass Transfer Rate ◽  
Falling Film ◽  
Film Evaporation ◽  
Falling Film Evaporation ◽  
Tube Geometry

Abstract This paper discusses about the effect of tube geometry and liquid feeder height on the heat transfer performance of falling film evaporation over the horizontal heated plain tubes. To investigate this, a two-dimensional computational fluid dynamics (CFD) model was developed, compared, and validated with published data available in the literature. A numerical simulation was carried out for varying liquid load, tube diameter, liquid feeder height, and corresponding changes in the heat transfer co-efficient (HTC), and mass transfer rate was recorded and analyzed. An attempt was also made to measure the thickness of the film around the tubes from the simulation model. Mechanisms that control the factors such as HTC, film thickness, and mass transfer were numerically investigated and discussed in this work. Numerical results indicated that low value of liquid film thickness appears approximately at the angular position of the range between 90 deg and 125 deg. Also the numerical investigation revealed that liquid film thickness decreases and HTC and mass transfer rate increases with the increase of feeder height. No remarkable change in film thickness was observed with increase in the tube diameter. This numerical study also proved that the prediction of thermally developed boundary region on the circumference of the tube could be possible in terms of mass transfer rate. It was also observed from the numerical study that the highest mass transfer rate takes place between the angle 135–165 deg near to the bottom of the tube.

scholarly journals On the Influence of Magnetic Field on Accretion Processes in CVs

2015 ◽  
Vol 2 (1) ◽  
pp. 60-65
Author(s):  
D. V. Bisikalo ◽  
A. G. Zhilkin
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
White Dwarf ◽  
Transfer Rate ◽  
Accretion Rate ◽  
Mass Transfer Rate ◽  
Rotation Velocity ◽  
Spin Rotation ◽  
Mhd Simulations ◽  
Intermediate Polars

We consider the influence of such parameters as the value of the proper magnetic field Ba and the spin-rotation velocity of the white dwarf on accretion processes in CVs. The results of 3D MHD simulations have shown that the accretion rate is a non-monotonic function of Ba: with growing Ba it raises in the intermediate polars and decreases in the polars. The maximal accretion rate occurs in the systems, transiting from the stage of intermediate polars to polars; it’s value reaches 60% of the initially set mass transfer rate. We have also shown that the acretion rate decreases with the growing<br />spin-rotation velocity of the white dwarf.

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