scholarly journals Natural convection in a square cavity with partially active vertical walls: Time-periodic boundary condition

2006 ◽  
Vol 2006 ◽  
pp. 1-16 ◽  
Author(s):  
N. Nithyadevi ◽  
P. Kandaswamy ◽  
S. Sivasankaran
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Active Regions ◽  
Governing Equations ◽  
Square Cavity ◽  
Side Walls ◽  
Vertical Walls ◽  
Volume Method ◽  
Time Periodic

A numerical study of transient natural convection in a square cavity with partly thermally active side walls is introduced. The thermally active regions of the side walls are periodic in time. Top and bottom of the cavity are adiabatic. Nine different positions of the thermally active zones are considered. The governing equations are solved using control volume method with power-law scheme. The results are obtained for various values of amplitude, period, and Grashof numbers ranging from104–106and different thermally active situations. It is found that the average heat transfer increases by increasing amplitude forP=1,5, and decreasing forP=3. The average Nusselt number behaves nonlinearly as a function of period.

scholarly journals Numerical Study of the Turbulent Natural Convection in a Trapezoidal Cavity: Influence of the Inclination of the Lateral Walls

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Boussinesq Approximation ◽  
Governing Equations ◽  
Square Cavity ◽  
Turbulent Natural Convection ◽  
Side Walls ◽  
Volume Method ◽  
Calculation Code

In this paper, we study the heat transfer in turbulent natural convection in a two- dimensional cavity with a trapezoidal section and isoscales filled out of air with as height H =2.5 m. In these conditions, the side walls are differentially heated while the horizontal walls are adiabatic. The k-ε turbulence model with a small Reynolds number was integrated in our calculation code. The governing equations of the problem were solved numerically by the commercial CFD code Fluent; which is based on the finite volume method and the Boussinesq approximation. The elaborated model is validated from the experimental results in the case of the turbulent flow in a square cavity. Then, the study was related primarily to the influence of the slope of the side walls of the cavity on the dynamic behavior and the heat transfer within the cavity.

Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

2016 ◽  
Vol 831 ◽  
pp. 83-91
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Cubical Enclosure ◽  
Simplec Algorithm ◽  
Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

Numerical Investigation of the Onset of Steady Natural Convection in a Square Cavity Partially Filled With a Single Porous Block

2014 ◽  
Author(s):  
Vinicius Daroz ◽  
Silvio L. M. Junqueira ◽  
Admilson T. Franco ◽  
José L. Lage
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Critical Rayleigh Number ◽  
Contour Plot ◽  
Viscous Effects ◽  
Square Cavity ◽  
Heterogeneous Model ◽  
Porous Block ◽  
Vertical Walls ◽  
Volume Method

The critical Rayleigh number at the onset of natural convection within a square cavity filled with a centralized porous block was investigated. The porous medium is modeled by using the heterogeneous model and the governing equations are solved for each phase separately. The thermal gradient is applied from the bottom to the top horizontal walls while the vertical walls are kept adiabatic. The amount of solid within the cavity was kept constant by fixing both external and internal porosity in 36% and 40%, respectively. The equations are solved using the Finite Volume Method and the interpolation scheme for the convective terms is the Hybrid Scheme. For the pressure-velocity coupling, the SIMPLEC method is used. The effects on the conductive-convective regime transition, reads critical Rayleigh Number, characterized by the average Nusselt number and the heatlines contour plot, was investigated by varying the Rayleigh number and the porous block permeability. The results show that the so called critical Rayleigh number is affected by the block permeability. As the permeability decreases, the flow tends to recirculate around the block being squeezed against the cavity walls and therefore, more susceptible to viscous effects. A correlation to the critical Rayleigh number is presented as a function of the agglomerate permeability showing that the higher the permeability the lower the amount of energy required to trigger the convection.

Laminar Natural Convection Inside a Wavy Enclosure Heated From Top and Uniformly Cooled From the Bottom and Both Sides

2005 ◽  
Author(s):  
Amaresh Dalal ◽  
Manab Kumar Das
Keyword(s):  
Natural Convection ◽  
Simple Algorithm ◽  
Governing Equations ◽  
Square Cavity ◽  
Integral Forms ◽  
Nusselt Number Distribution ◽  
Laminar Natural Convection ◽  
Lower Temperature ◽  
Volume Method ◽  
Spatially Varying

In the present paper, natural convection inside a square cavity with one and three undulations on the top wall has been carried out. The top wall is heated by a spatially varying temperature and other three walls are kept constant lower temperature. The integral forms of the governing equations are solved numerically using finite-volume method in non-orthogonal body-fitted coordinate system. SIMPLE algorithm with higher-order up-winding scheme are used. The streamlines and isothermal lines are presented for different Rayleigh number (103-106) and a fluid having Prandtl number 0.71. Results are presented in the form of local and average Nusselt number distribution for two different undulations (1 and 3) with wave amplitude of 0.05.

A Numerical Study of Natural Convection in a Cavity With Two Fins Attached to Its Vertical Walls

2007 ◽  
Author(s):  
G. A. Sheikhzadeh ◽  
M. Pirmohammadi ◽  
M. Ghassemi
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Square Cavity ◽  
Vertical Walls ◽  
The Mean ◽  
Energy Equations ◽  
Rayleigh Numbers

Numerical study natural convection heat transfer inside a differentially heated square cavity with adiabatic horizontal walls and vertical isothermal walls is investigated. Two perfectly conductive thin fins are attached to the isothermal walls. To solve the governing differential mass, momentum and energy equations a finite volume code based on Pantenkar’s simpler method is developed and utilized. The results are presented in form of streamlines, isotherms as well as Nusselt number for Rayleigh number ranging from 104 up to 107. It is shown that the mean Nusselt number is affected by the position of the fins and length of the fins as well as the Rayleigh number. It is also observed that maximum Nusselt number occurs about the middle of the enclosure where Lf is grater the 0.5. In addition the Nusselt number stays constant and does not varies with width of the cavity (lf) when Lf is equal to 0.5 and Rayleigh number is equal to 104 and 107 as well as when Lf is equal to 0.6 and low Rayleigh numbers.

scholarly journals Isotherms and Streamlines for 2D Lid Driven Square Cavity

2021 ◽  
Vol 10 (11) ◽  
pp. 97-99
Author(s):  
Garepally Srinivas ◽  
◽  
A. V. Ramana Kumari ◽  
Narayana Vekamulla ◽  
◽  
...  
Keyword(s):  
Reynolds Number ◽  
Richardson Number ◽  
Thermal Characteristics ◽  
Cavity Flow ◽  
Control Parameters ◽  
Governing Equations ◽  
Square Cavity ◽  
Isothermal Temperature ◽  
Vertical Walls ◽  
Volume Method

Analysis of lid driven square cavity flow of air with three different ranges of Ri and Re are analyzed using numerically. Adiabatic temperature is maintained at horizontal walls and isothermal temperature is established at the vertical walls in which the top wall is assumed to slide with a uniform speed. Finite volume method techniques have used to solve non dimensional governing equations. To visualize the flow and thermal characteristics, the control parameters, the Richardson number (Ri) and Reynolds number (Re) and in the range of 0.001 ≤ Ri ≤ 10 and 100 ≤ Re ≤ 400 are used for streamlines and isotherms.

scholarly journals Numerical study of the coupled natural convection with surface radiation in a cylindrical annular enclosure

2020 ◽  
Vol 330 ◽  
pp. 01029
Author(s):  
Mohamed Amine MEDEBBER ◽  
Abderrahmane AISSA ◽  
Belkacem OULD SAID ◽  
Noureddine RETIEL ◽  
Mohammed EL GANAOUI
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Surface Radiation ◽  
Navier Stokes ◽  
Simpler Algorithm ◽  
Energy Equations ◽  
Volume Method ◽  
Rayleigh Numbers ◽  
Total Average

The interaction of natural convection with thermal radiation of black surfaces in a cylindrical enclosure filled with air has been numerically investigated. The steady-state continuity, Navier-Stokes and energy equations were discretized using the control volume method and solved numerically via the SIMPLER algorithm. Effects of Rayleigh number (Ra), wall emissivity (εp) and height ratio parameter (X) are studied. The result shows that surface radiation significantly altered the temperature distribution and the flow patterns, especially at higher Rayleigh numbers. The total average Nusselt number has also been discussed for valuating heat transfer through the enclosure.

Turbulent Natural Convection in Horizontal Composite Cavities

2003 ◽  
Author(s):  
Edimilson J. Braga ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Natural Convection ◽  
Computational Domain ◽  
Turbulent Model ◽  
Governing Equations ◽  
Square Cavity ◽  
Thermal Systems ◽  
Turbulent Natural Convection ◽  
Solid Region ◽  
Treat All ◽  
Volume Method

Turbulent natural convection in a two-dimensional horizontal composite square cavity, isothermally heated at the left side and cooled from the opposing surface, is numerically analyzed using the finite volume method. The composite square cavity is formed by three distinct regions, namely, clear, porous and solid region. Accordingly, the development of a numerical tool able to treat all these regions as one computational domain is of advantage for engineering design of thermal systems. Governing equations are written in terms of primitive variables and are recast into a general form. It was found that the fluid begins to permeate the porous medium for values of Ra greater than 106. Nusselt number values show that for the range of Ra analyzed there are no significant variation between the laminar and turbulent model solution..

Numerical Simulation of Natural Convection in a Mold

2010 ◽  
Vol 297-301 ◽  
pp. 456-461
Author(s):  
Mohsen Pirmohammadi ◽  
Ghanbar Ali Sheikhzadeh ◽  
Majid Ghassemi ◽  
Mohsen Hamedi
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Linear Equations ◽  
Convection Heat Transfer ◽  
Square Enclosure ◽  
Simpler Algorithm ◽  
Volume Method ◽  
Hot Surface

Numerical study of natural convection heat transfer inside a differentially heated square enclosure with adiabatic horizontal walls and vertical isothermal walls is investigated. Two insulated ribs are symmetrically located on horizontal walls. The governing non-linear equations are solved in a two-dimensional domain using a control volume method and the SIMPLER algorithm for the velocity–pressure coupling is employed. The results will be presented in forms of streamlines, isotherms and Nusselt number for Rayleigh number 106. It is shown that for small rib height the isotherms indicate the laminar boundary regime with high temperature gradient near the bottom of the hot surface and the top of cold one. However, as rib height increases this boundary layer is vanished. Also it is found that as the length and height of the ribs increase the mean Nusselt number decreases.

Natural Convection From a Layered Porous Cavity With Non-Uniform Sublayers

2007 ◽  
Author(s):  
R. L. Marvel ◽  
F. C. Lai
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
System Analysis ◽  
Numerical Study ◽  
Temperature Fields ◽  
Square Cavity ◽  
Porous Cavity ◽  
Differential Heating ◽  
Vertical Walls

A numerical study has been performed to further investigate the flow and temperature fields in layered porous cavity. The geometry considered is a square cavity with 3 or 4 non-uniform sublayers and is subjected to differential heating from the vertical walls. The results obtained are used to further evaluate the feasibility of using the lumped-system analysis for heat transfer in layered porous cavities as proposed in the previous study. To this end, the effective permeabilities based on the arithmetic and harmonic averaging schemes are examined for their use in the conjunction with the lumped-system analysis.

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