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.

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.

Spiral-Plate Heat Exchanger Effectiveness With Equal Capacitance Rates

2005 ◽  
Author(s):  
Louis C. Burmeister
Keyword(s):  
Heat Exchanger ◽  
Plate Heat Exchanger ◽  
Close Approximation ◽  
Transfer Coefficients ◽  
Plate Heat ◽  
Heat Transfer Coefficients ◽  
Outer Periphery ◽  
Large Heat ◽  
The Difference ◽  
Spiral Plate

A formula is derived for the dependence of heat exchanger effectiveness on the number of transfer units for a spiral-plate heat exchanger with equal capacitance rates. The difference-differential equations that describe the temperature distributions of the two counter-flowing fluids, neglecting thermal radiation, are solved symbolically to close approximation. Provision is made for offset inlet and exit of the hot and cold fluids at the outer periphery and for large heat transfer coefficients in entrance regions. The peak effectiveness and the number of transfer units at which it occurs are predicted.

scholarly journals Comparison and analysis of calculation of Bridge backwater based on Mike21 hydrodynamic model

2021 ◽  
Vol 233 ◽  
pp. 03043
Author(s):  
Jiang Chuan Liu ◽  
Zhu Qiu Hu ◽  
Mao Yuan Zhu
Keyword(s):  
Theoretical Basis ◽  
Impact Analysis ◽  
Navier Stokes ◽  
Efficiency Coefficient ◽  
Navier Stokes Equation ◽  
The Real ◽  
Comparison And Analysis ◽  
Simulation Results ◽  
The Difference ◽  
Local Water

The construction of bridges and other structures across the river will affect the flood discharge capacity and local water potential of the river.Based on navier-Stokes equation of MIKE21FM hydrodynamic module, this paper carries out two-dimensional numerical simulation of part of Shixi River. By optimizing the grid near the piers to reduce the difference brought by the terrain generalized grid of the real river, it simulates and analyzes the length of the curve of yong-high and Yong-water under different flood frequencies,the Nash-Sutcliffe efficiency coefficient and relative error analysis are used to verify the rationality of the results. The simulation results can accurately reflect the real changes of river water level, It provides a theoretical basis for flood impact analysis.

Conditions for Equivalency of Countercurrent Vessel Heat Transfer Formulations

1999 ◽  
Vol 121 (5) ◽  
pp. 514-520 ◽  
Author(s):  
R. B. Roemer
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Temperature Difference ◽  
Bulk Temperature ◽  
Transfer Coefficients ◽  
Bulk Fluid ◽  
Heat Transfer Coefficients ◽  
The Difference ◽  
Convective Heat Transfer Coefficients

Previous models of countercurrent blood vessel heat transfer have used one of two, different, equally valid but previously unreconciled formulations, based either on: (1) the difference between the arterial and venous vessels’ average wall temperatures, or (2) the difference between those vessels’ blood bulk fluid temperatures. This paper shows that these two formulations are only equivalent when the four, previously undefined, “convective heat transfer coefficients” that are used in the bulk temperature difference formulation (two coefficients each for the artery and vein) have very specific, problem-dependent relationships to the standard convective heat transfer coefficients. (The average wall temperature formulation uses those standard coefficients correctly.) The correct values of these bulk temperature difference formulation “convective heat transfer coefficients” are shown to be either: (1) specific functions of (a) the tissue conduction resistances, (b) the standard convective heat transfer coefficients, and (c) the independently specified bulk arterial, bulk venous and tissue temperatures, or (2) arbitrary, user defined values. Thus, they are generally not equivalent to the standard convective heat transfer coefficients that are regularly used, and must change values depending on the blood and tissue temperatures. This dependence can significantly limit the convenience and usefulness of the bulk temperature difference formulations.

scholarly journals Closed-Form Non-Stationary Solutionsfor Thermo and Chemovibrational Viscous Flows

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 175 ◽  
Author(s):  
Dmitry Bratsun ◽  
Vladimir Vyatkin
Keyword(s):  
Viscous Flow ◽  
Closed Form ◽  
General Procedure ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Chemical Transformations ◽  
Navier Stokes Equation ◽  
Harmonic Vibrations

A class of closed-form exact solutions for the Navier–Stokes equation written in the Boussinesq approximation is discussed. Solutions describe the motion of a non-homogeneous reacting fluid subjected to harmonic vibrations of low or finite frequency. Inhomogeneity of the medium arises due to the transversal density gradient which appears as a result of the exothermicity and chemical transformations due to a reaction. Ultimately, the physical mechanism of fluid motion is the unequal effect of a variable inertial field on laminar sublayers of different densities. We derive the solutions for several problems for thermo- and chemovibrational convections including the viscous flow of heat-generating fluid either in a plain layer or in a closed pipe and the viscous flow of fluid reacting according to a first-order chemical scheme under harmonic vibrations. Closed-form analytical expressions for fluid velocity, pressure, temperature, and reagent concentration are derived for each case. A general procedure to derive the exact solution is discussed.

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.

Heat Transfer Experiments of Mini-Tube Bank

2009 ◽  
Author(s):  
Yutaka Ebihara ◽  
Atsushi Katsuta ◽  
Yasuo Koizumi ◽  
Hiroyasu Ohtake
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Test Section ◽  
Square Lattice ◽  
Test Fluid ◽  
Wake Region ◽  
Transfer Coefficients ◽  
Tube Bank ◽  
Heat Transfer Coefficients ◽  
The Difference

Heat transfer and flow behavior in the mini rod bank were examined. The tubes are simulated with a 1 mm diameter nickel wire. The tube bank was composed of the 5×5 square-lattice array and the 5×5 staggered array. The tube banks were arranged in the flow channel of 30 mm wide or 15 mm wide, 15 mm high and 480 mm long. Water was used as the test fluid. A flow rate was varied in the range of the Reynolds number Re = uD/ν of 1 ∼ 800, where D is the tube diameter. The approaching velocity of fluid in the channel was in the range of 0.0036 m/s ∼ 0.68 m/s. Experiments were performed at atmospheric pressure. The measured heat transfer coefficients of the rows after the second row were lower than those of the first row and the difference between those increased as the Reynolds number was increased. The difference turned to decrease around Reynolds number = 50 in the 15 mm wide test section experiments of the square–lattice array and around Reynolds number = 200 in the 30 mm wide test section experiments of the staggered array. The heat transfer coefficients reached back to the first row value around Re = 400 in the former experiments. It was confirmed through the present results and the previous results that the heat transfer in the rear rows is deteriorated by the flow stagnation in the wake region of the preceding rod and the deterioration is recovered as the Reynolds number is increased since the wake region becomes disturbed.

scholarly journals Modelling of temperature distribution along PCB thickness in different substrates during reflow

Circuit World ◽  
2019 ◽  
Vol 46 (2) ◽  
pp. 85-92
Author(s):  
Daniel Straubinger ◽  
István Bozsóki ◽  
David Bušek ◽  
Balázs Illés ◽  
Attila Géczy
Keyword(s):  
Heat Transfer ◽  
Printed Circuit Board ◽  
Vapour Phase ◽  
Circuit Board ◽  
Transfer Coefficients ◽  
Content Type ◽  
Printed Circuit ◽  
Heat Transfer Coefficients ◽  
Significant Temperature ◽  
The Difference

Purpose In this paper, analytical modelling of heat distribution along the thickness of different printed circuit board (PCB) substrates is presented according to the 1 D heat transient conduction problem. This paper aims to reveal differences between the substrates and the geometry configurations and elaborate on further application of explicit modelling. Design/methodology/approach Different substrates were considered: classic FR4 and polyimide, ceramics (BeO, Al2O3) and novel biodegradables (polylactic-acid [PLA] and cellulose acetate [CA]). The board thicknesses were given in 0.25 mm steps. Results are calculated for heat transfer coefficients of convection and vapour phase (condensation) soldering. Even heat transfer is assumed on both PCB sides. Findings It was found that temperature distributions along PCB thicknesses are mostly negligible from solder joint formation aspects, and most of the materials can be used in explicit reflow profile modelling. However PLA shows significant temperature differences, pointing to possible modelling imprecisions. It was also shown, that while the difference between midplane and surface temperatures mainly depend on thermal diffusivity, the time to reach solder alloy melting point on the surface depends on volumetric heat capacity. Originality/value Results validate the applicability of explicit heat transfer modelling of PCBs during reflow for different heat transfer methods. The results can be incorporated into more complex simulations and profile predicting algorithms for industrial ovens controlled in the wake of Industry 4.0 directives for better temperature control and ultimately higher soldering quality.

Aero-Thermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets: Part II—Heat Transfer Analysis

2008 ◽  
Author(s):  
Filippo Coletti ◽  
Alessandro Armellini ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Heat Transfer Analysis ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Present Contribution ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Rib Roughened

The present contribution addresses the aero-thermal experimental and computational study of a trapezoidal cross-section model simulating a trailing edge cooling cavity with one rib-roughened wall and slots along two opposite walls. Highly resolved heat transfer distributions for the geometry with and without ribs are achieved using a steady state liquid crystals method in part II of this paper. The reference Reynolds number, defined at the entrance of the test section, is set at 67500 for all the experiments. Comparisons are made with the flow field visualizations presented in part I of the paper. The results show the dramatic impact of the flow structures on the local and global heat transfer coefficients along the cavity walls. Of particular importance is the jet deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained using the finite volume, Reynolds-Averaged Navier-Stokes solver CEDRE.

A Comparison of the Transient and Heated-Coating Methods for the Measurement of Local Heat Transfer Coefficients on a Pin Fin

1989 ◽  
Vol 111 (4) ◽  
pp. 877-881 ◽  
Author(s):  
J. W. Baughn ◽  
P. T. Ireland ◽  
T. V. Jones ◽  
N. Saniei
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Uniform Heat Flux ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
The Difference

Measurements of the local heat transfer coefficients on a pin fin (i.e., a short cylinder in crossflow) in a duct have been made using two methods, both of which employ liquid crystals to map an isotherm on the surface. The transient method uses the liquid crystal to determine the transient response of the surface temperature to a change in the fluid temperature. The local heat transfer coefficient is determined from the surface response time and the thermal properties of the substrate. The heated-coating method uses an electrically heated coating (vacuum-deposited gold in this case) to provide a uniform heat flux, while the liquid crystal is used to locate an isotherm on the surface. The two methods compare well, especially the value obtained near the center stagnation point of the pin fin where the difference in the thermal boundary condition of the two methods has little effect. They are close but differ somewhat in other regions.

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