Stationary fluid convection modes with a Gaussian viscosity dependence of temterature

2016 ◽  
Vol 11 (2) ◽  
pp. 218-225
Author(s):  
V.S. Kuleshov
Keyword(s):  
Computer Code ◽  
Boussinesq Approximation ◽  
Simple Type ◽  
Transfer Coefficients ◽  
Convective Flows ◽  
Heat Transfer Coefficients ◽  
Fluid Convection ◽  
Flat Cell ◽  
Volume Method ◽  
Viscosity Dependence

The results of a numerical modeling of thermo-gravitational convection of abnormally thermo-viscous fluid in a closed square cavity with two vertical adiabatic walls and two horizontal isothermal walls are presented. A model Newtonian liquid for which the dependence of viscosity on temperature is described by a bell function (Gaussian curve) is considered. The natural convection of inhomogeneous liquid is described by the closed mathematical model based on the continuous mechanics equations written in Oberbeck-Boussinesq approximation, where the fluid density is a linear function of temperature. To simulate the fluid flow dynamics, the modified computer code based on the implicit finite volume method and SIMPLE-type algorithm with the second-order temporal accuracy is realized using multiprocessor technology. The effect of the viscosity abnormality on stationary modes of convective flows are studied, the integral heat transfer coefficients in a flat cell are calculated.

scholarly journals Numerical Analysis of Thermal and Aerodynamic Fields in a Channel with Cascaded Baffles

2017 ◽  
Vol 62 (1) ◽  
pp. 16 ◽  
Author(s):  
Younes Menni ◽  
Ahmed Azzi
Keyword(s):  
Fluid Dynamic ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Computational Fluid Dynamic Analysis ◽  
Heat Transfer Coefficients ◽  
Discretization Algorithm ◽  
Volume Method ◽  
The Impact

A computational fluid dynamic analysis of thermal and aerodynamic fields for an incompressible steady-state flow of a Newtonian fluid through a two-dimensional horizontal rectangular section channel with upper and lower wall-attached, vertical, staggered, transverse, cascaded rectangular-triangular (CRT), solid-type baffles is carried out in the present paper using the Commercial, Computational Fluid Dynamics, software FLUENT. The flow model is governed by the Reynolds averaged Navier-Stokes (RANS) equations with the SST k-ω turbulence model and the energy equation. The finite volume method (FVM) with the SIMPLE-discretization algorithm is applied for the solution of the problem. The computations are carried out in the turbulent regime for different Reynolds numbers. In this study, thermo-aeraulic fields, dimensionless axial profiles of velocity, skin friction coefficients, local and average heat transfer coefficients, and thermal enhancement factor were investigated, at constant surface temperature condition along the heated upper wall of the channel, for all the geometry under investigation and chosen for various stations. The impact of the cascaded rectangular-triangular geometry of the baffle on the thermal and dynamic behavior of air is shown and this in comparing the data of this obstacle type with those of the simple flat rectangular-shaped baffle. This CFD analysis can be a real application in the field of heat exchangers, solar air collectors, and electronic equipments.

Parametric Study of Phase Change Suspension Flow in Microchannels

2003 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Phase Change ◽  
Flow Condition ◽  
Computer Code ◽  
Cfd Modeling ◽  
Transfer Coefficients ◽  
Circular Duct ◽  
Heat Transfer Coefficients ◽  
Melting Region

A continuum model is applied to the numerical simulation of the laminar hydrodynamic and heat-transfer characteristics of suspension with phase change material (PCM) particles in a microchannel. The analytical/numerical formulation based on CFD modeling technique, and the computer code is developed. Local wall-to-suspension heat transfer coefficients are calculated by the simultaneous solution of the conservation of mass, momentum and thermal energy equations. By providing detailed information on the local behavior of the wall-to-suspension heat transfer coefficients, preliminary calculations expose that there exists a particle-depleted layer next to the wall under the laminar flow condition. It plays an important role on the heat transfer between the suspension and the wall under the laminar flow condition. The heat transfer coefficient increases and reaches a peak value in the melting region. The benefits on the enhancement of heat transfer and the reduction of wall temperature and mean temperature by employing the MCPCM particle are mainly in the melting region. The preliminary results agree very well with the experimental observations and measurement on the flow and heat transfer of microencapsulated PCM slurry in circular duct. It interprets the observation in the literature where heat transfer between the suspension and the wall is weaker in non-melting region and melted region than that between the pure fluid and the wall for laminar flow conditions.

INFLUENCE OF ELECTROLYTE COMPOSITION AND OVERHEATING ON THE SIDELEDGE IN THE ALUMINUM CELL

2018 ◽  
pp. 24-30 ◽  
Author(s):  
V. V. Stakhanov ◽  
A. A. Redkin ◽  
Yu. P. Zaikov ◽  
A. E. Galashev
Keyword(s):  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Navier Stokes Equation ◽  
Cryolite Ratio ◽  
Heat Transfer Coefficients ◽  
Aluminum Smelting ◽  
Block Wall ◽  
The Difference ◽  
Aluminum Cell

The paper presents a theoretical study conducted to investigate the effect that the chemical composition of electrolyte and its overheating have on the size of sideledge formed in an aluminum smelting bath. Three electrolyte compositions were chosen: (1) sodium cryolite with the cryolite ratio CR = 2,7; (2) cryolite CR = 2,7 + 5 wt.% CaF2; (3) cryolite CR = 2,7 + 5 wt.% CaF2 + 5 wt.% Al2О3. The electrolyte liquidus overheating temperatures were 5, 10, 15 and 20 °C. Calculations were performed using the finite element method. A simplified design of an aluminum cell was used with a prebaked anode. The temperature field was calculated using a mathematical model based on the Boussinesq approximation, which contains the Navier–Stokes equation as well as thermal conductivity and incompressibility equations. The key role of electrolyte overheating in sideledge formation was established. The resulting sideledge profile depends on the heat transfer coefficients and thermophysical properties of materials. The smallest sideledge thickness with the same electrolyte overheating was observed in cryolite composition 3, and the profiles of the formed sideledge for samples 1 and 2 were nearly the same. The thickness of the sideledge formed with a 5 degree overheating exceeded 7 cm and the difference in temperature between the sideledge in contact with electrolyte and the side block wall was 20–25 degrees. It was found that the virtually total disappearance of the sideledge occurs at electrolyte liquidus overheating by 20 degrees.

High Atwood Number Effects in Buoyancy Driven Flows

2006 ◽  
Author(s):  
Malcolm J. Andrews ◽  
Farzaneh F. Jebrail ◽  
Arindam Banerjee
Keyword(s):  
Heat Transfer ◽  
Boussinesq Approximation ◽  
Large Temperature ◽  
Transfer Coefficients ◽  
Future Directions ◽  
Buoyant Plumes ◽  
Heat Transfer Coefficients ◽  
Buoyancy Driven Flows ◽  
Recent Experimental Work ◽  
Atwood Number

High Atwood number (non-dimensional density difference) effects in buoyancy driven flows are discussed. Buoyancy driven (natural convection) flows may be treated as Boussinesq for small Atwood number, but as Atwood number increases (>0.1, i.e. large temperature differences) the Boussinesq approximation is no longer valid and a distinct "bubble" and "spike" geometry of Rayleigh-Taylor buoyant plumes is formed. Aside from asymmetry in the flow the Atwood number also affects key turbulent mix parameters such as the molecular mix, and heat transfer coefficients. This paper presents recent experimental work being performed in the buoyancy driven mix laboratory at Texas A&M University, using air/helium as mixing components (upto At ~ 0.5). Corresponding numerical simulations of the experiments performed at Los Alamos is also presented, and future directions for the research discussed.

Numerical Study of Turbulent Flow Through Rib-Roughened Channels With Mist Injection

2014 ◽  
Author(s):  
Fifi N. M. Elwekeel ◽  
Qun Zheng ◽  
Antar M. M. Abdala
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Cross Sections ◽  
Numerical Study ◽  
Turbulence Models ◽  
Uniform Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Sst Turbulence Model ◽  
Volume Method

This study investigated heat transfer characteristics on various shaped ribs on the lower channel wall using steam and steam/mist as cooling fluid. The lower wall is subjected to a uniform heat flux condition while others walls are insulated. Calculations are carried out for ribs with square ribs (case A), triangular ribs (case B), trapezoidal ribs (case C) and (case D) cross sections over a range of Reynolds numbers (14000–35000), constant mist mass fraction (6%) and fixed rib height and pitch. To investigate turbulence model effects, computations based on a finite volume method, are carried out by utilizing three turbulence models: the standard k-ω, Omega Reynolds Stress (ωRS) and Shear Stress Transport (SST) turbulence models. The predicted results from using several turbulence models reveal that the SST turbulence model provide better agreement with available measurements than others. It is found that the heat transfer coefficients are enhanced in ribbed channels with injection of a small amount of mist. The steam/mist provides the higher heat transfer enhancement over steam when trapezoidal shaped ribs (38°, case C).

R&D of the Next Generation Safety Analysis Methods for Fast Reactors With New Computational Science and Technology: 4 — Experimental Analyses by SIMMER-III for the Integral Verification of COMPASS

2008 ◽  
Author(s):  
Hidemasa Yamano ◽  
Yoshiharu Tobita
Keyword(s):  
Heat Transfer ◽  
Computer Code ◽  
Freezing Behavior ◽  
Computational Science ◽  
Transfer Coefficients ◽  
Experimental Database ◽  
Heat Transfer Coefficients ◽  
Experimental Analyses ◽  
Good Agreement ◽  
Transient Heat Flux

This paper describes experimental analyses using the SIMMER-III computer code, which were precedently carried out to give boundary conditions for the integral verification of the new COMPASS code, which is based on MPS method. Two topics of key phenomena in core disruptive accidents were presented in this paper: molten fuel freezing and dispersion; and boiling behavior of molten fuel pool. Related experimental database are reviewed to select appropriate experiments. To analyze the fuel freezing behavior, the GEYSER out-of-pile and the CABRI-EFM1 in-pile experiments were selected. The SIMMER-III calculations were in good agreement with fuel penetration lengths measured in a series of the GEYSER experiments. The fuel freezing behavior in the CABRI-EFM1 experiment was also reasonably simulated by SIMMER-III. The boiling pool consisting principally of molten fuel/steel mixtures is characterized by the heat transfer between fuel and steel. The CABRI-TPA2 experiment has suggested low transient heat flux from fuel to steel due to a steel vapor blanketing around a steel droplet. SIMMER-III well simulated the steel boiling behavior observed in the CABRI-TPA2 experiment by applying reduced heat transfer coefficients between fuel and steel. These experimental analyses by SIMMER-III have also identified key processes to be clarified by mesoscopic simulations using the COMPASS code.

Development of Web Based Computer Package for the Simulation of Thermal Desalination Processes

2007 ◽  
Vol 2 (3) ◽  
Author(s):  
Nabil Abdel-Jabbar ◽  
Farouq S. Mjalli ◽  
Hazim Qiblawey ◽  
Hisham Ettouney
Keyword(s):  
Heat Transfer ◽  
Process Model ◽  
Computer Code ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Thermal Desalination ◽  
Actual Field ◽  
Computer Package ◽  
Design Calculations ◽  
User Friendly

A computer package based on visual basic code is developed for single and multiple effect evaporation desalination systems (SEE and MEE). The package features design calculations of heat transfer area, power consumption, and costing. The package is user-friendly and is equipped with interactive menus for report and form printing, file saving and retrieving, help files, and tutorial. The computer code is designed to run a default design case and also allows the user to change variables within pre-specified practical ranges. A rigorous process model is used in the package, which is based on detailed fundamental material and energy balance equations, well-proven correlations for the heat transfer coefficients, physical properties, and thermodynamic losses. Illustrations of the package displays are presented together with a number of case studies. Model predictions generated from the code are validated against actual field data and they showed a very good agreement. Future plans involve development of design simulator for the multistage flash desalination (MSF) and reverse osmosis (RO).

Numerical Calculation of Heat Transfer Coefficient of Liquid Flow With NPCM in Microchannels

2003 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Flow Condition ◽  
Computer Code ◽  
Thermal Capacity ◽  
Cfd Modeling ◽  
Transfer Coefficients ◽  
Qualitative Comparison ◽  
Circular Duct ◽  
Heat Transfer Coefficients

A continuum model is applied to the numerical simulation of the laminar hydrodynamic and heat-transfer characteristics of suspension with nano phase change material (NPCM) particles in a microchannel. The analytical/numerical formulation based on CFD modeling technique, and the computer code is developed. Local wall-to-suspension heat transfer coefficients are calculated by the simultaneous solution of the conservation of mass, momentum and thermal energy equations. By providing detailed information on the local behavior of the wall-to-suspension heat transfer coefficients, preliminary calculations expose that there exists a particle-depleted layer next to the wall under the laminar flow condition. It plays an important role on the heat transfer between the suspension and the wall under the laminar flow condition. The main contribution of NPCM particles is the increase in the thermal capacity under the laminar flow condition. The qualitative comparison with the experimental observations and measurements on the flow and heat transfer of microencapsulated PCM slurry in circular duct indicates that the preliminary results are reasonable. It interprets the observation in the literature where heat transfer between the suspension and the wall is weaker than that between the pure fluid and the wall for laminar flow conditions.

Simulation of Corrected Mass Flow and Non-Adiabatic Efficiency on a Turbocharger

2013 ◽  
Vol 388 ◽  
pp. 23-28
Author(s):  
A. Mohd Ibthisham ◽  
Srithar Rajoo ◽  
Amer Nordin Darus ◽  
Mazlan Abdul Wahid ◽  
Mohsin Mohd Sies ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Mass Flow ◽  
Working Condition ◽  
Three Dimensional ◽  
Actual Condition ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Volume Method ◽  
The Heat Transfer Coefficient

The aim of this project is to evaluate turbine’s performance based on its actual condition. Holset H3B nozzles turbine geometry was used as simulation model. Turbine’s actual working condition was simulated using finite volume method (FVM). Three-dimensional Navier Stoke equations with heat convection loss via turbine volute are solved. The parameters studied are corrected mass flow and turbine’s efficiency at different heat transfer coefficients. Temperature difference within turbine’s volute is the major factor that deteriorates turbine’s efficiency. It is found that the higher the heat transfer coefficient, the lower turbine’s efficiency will be.

Numerical Analysis of Heat Conduction in Cooling of Aluminum Extrusion

2002 ◽  
Author(s):  
Nicola Bianco ◽  
Oronzio Manca
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Cooling System ◽  
Heat Conduction Problem ◽  
Aluminum Extrusion ◽  
Transfer Coefficients ◽  
Lower Velocity ◽  
Heat Transfer Coefficients ◽  
Water Sprays ◽  
Volume Method

A thermal analysis of the cooling of an extruded aluminum alloy by means of water sprays is carried out. The heat conduction problem has been solved numerically by means of a finite volume method. The heat transfer coefficients used in the boundary conditions has been evaluated by means of spray heat transfer correlations, which relate these coefficients to the spray hydrodynamic parameters. The influence of the number of sprays and of the solid velocity has been investigated. Results show that the efficiency of the cooling system decreases as the number of jets increases. The efficiency of each spray increases with the velocity for the same number of sprays. As the workpiece velocity increases it needs to increase the number of sprays to obtain the same temperature difference between the entry and the exit of the cooling system. The greater the number of sprays related to the case with lower velocity, the smaller the increase of the number of sprays.

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