Numerical Study of Natural Convection in a Partitioned Cavity

2008 ◽  
Author(s):  
M. Pirmohammadi ◽  
M. Ghassemi ◽  
G. A. Sheikhzadeh
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Numerical Study ◽  
Temperature Gradients ◽  
Cold Wall ◽  
Governing Equations ◽  
Square Cavity ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Energy Equations

The purpose of this study is to investigate the effect of insulated horizontal baffle placed at the hot wall of a differentially heated square cavity. The vertical walls are at different temperatures while the horizontal walls are adiabatic. In our formulation of governing equations, mass, momentum and the energy equations are applied to the cavity and the baffles. To solve the governing differential equations a finite volume code based on Patankar’s SIMPLER method is utilized [1]. The Results are presented for Rayleigh number from 104 up to 106 and are in form of streamlines, isotherms and Nusselt number. The baffle causes that at low Rayleigh number the horizontal isotherms are replaced by nearly vertical ones, specially around the baffle. Also it is found that thermal boundary layers are thickened, and the temperature gradients at the cold wall are reduced from their values for the case without baffle and this implies that a reduction in the heat transfer through the cavity occurs.

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.

Study of mixed convection in closed enclosure with a ceiling fan

2019 ◽  
Vol 86 (2) ◽  
pp. 20902 ◽  
Author(s):  
Lyes Nasseri ◽  
Omar Rahli ◽  
Djamel Eddine Ameziani ◽  
Rachid Bennacer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rayleigh Number ◽  
Lattice Boltzmann ◽  
Transfer Rate ◽  
Numerical Study ◽  
Square Cavity ◽  
Flow Intensity ◽  
Vertical Walls ◽  
Boltzmann Method

This paper presents a numerical study of heat transfer by convection in a square cavity. The vertical walls of the cavity are differentially heated and the horizontal ones are considered adiabatic. A fan is placed in the middle of the cavity and releases a jet down. Numerical simulation was performed using the lattice Boltzmann method to show the flow patterns and the heat flux depending on the Rayleigh number (thermal convection intensity) and the Reynolds number (fan-driven flow intensity). A parametric study was performed presenting the influence of Reynolds number (20 ≤ Re ≤ 500), Rayleigh number (10 ≤ Ra ≤ 106) and the fan position (0.2 ≤ HF ≤ 0.8). In forced convection mode, the flow structure has been mapped according to the position and the power of the fan. Three structures have emerged: two symmetrical cells, four symmetrical cells and asymmetrical structure. It has been observed that the heat transfer rate increases with the rise of Reynolds number and the reduction of the distance of the fan position from the ceiling. For the latter one, an unfavorable evolution of Nusselt number is observed for Ra > 104.

NUMERICAL STUDY OF LAMINAR CONVECTION AND THERMOSOLUTAL CONVECTION IN A TWO-DIMENSIONAL TRAPEZOIDAL CAVITY

1994 ◽  
Vol 18 (3) ◽  
pp. 207-224 ◽  
Author(s):  
M. Lacroix
Keyword(s):  
Schmidt Number ◽  
Numerical Study ◽  
Temperature Gradients ◽  
Thermosolutal Convection ◽  
Governing Equations ◽  
Concentration Gradients ◽  
Height Ratio ◽  
Vertical Walls ◽  
Laminar Convection ◽  
Rayleigh Numbers

Heat transfer driven by temperature gradients and simultaneous temperature and concentration gradients has been studied numerically for horizontal prismatic cavities of trapezoidal section having a hot horizontal base, a cool inclined top and insulated vertical walls. Results are presented for a cavity with width-to-mean height ratio of 4, thermal and concentration Rayleigh numbers up to 106 and 5.105 respectively, and top surface inclinations from 0 to 15 deg to the horizontal. The Prandtl and the Schmidt number used are 0.71 and 0.6 respectively. The governing equations are expressed in terms of stream function and vorticity and body-fitted coordinates are used for mapping the sloping top wall. As the inclination of the top surface is increased, the Nusselt and Sherwood numbers decrease. The effect of opposing thermal and concentration gradients on the Nusselt and Sherwood numbers is however more important than the effect of the inclination of the top surface. Theoretical Nusselt and Sherwood numbers are compared with available experimental data.

Influence of Non Uniform Boundary Conditions on Laminar Free Convection in Wavy Square Cavity With Partial Partitions

Volume 1 ◽  
2004 ◽  
Author(s):  
A. Sabeur-Bendehina ◽  
M. Aounallah ◽  
L. Adjlout ◽  
O. Imine ◽  
B. Imine
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Numerical Study ◽  
Laminar Regime ◽  
Uniform Temperature ◽  
Square Cavity ◽  
Vertical Walls ◽  
The Mean ◽  
Rayleigh Numbers ◽  
Partial Partitions

In the present work, a numerical study of the effect of non uniform boundary conditions on the heat transfer by natural convection in cavities with partial partitions is investigated for the laminar regime. This problem is solved by using the partial differential equations which are the equation of mass, momentum and energy. The tests were performed for different boundary conditions and different Rayleigh numbers while the Prandtl number was kept constant. Four geometrical configurations were considered namely three and five undulations with increasing and decreasing partition length. The results obtained show that the non uniform temperature in the vertical walls affects the flow and the heat transfer. The mean Nusselt number decreases comparing with the heat transfer in the undulated square cavity without partitions for all non uniform boundary conditions tested.

Numerical study of the fin effect on mixed convection heat transfer in a lid-driven cavity

2010 ◽  
Vol 225 (2) ◽  
pp. 397-406 ◽  
Author(s):  
A A R Darzi ◽  
M Farhadi ◽  
K Sedighi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Richardson Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Driven Cavity ◽  
Ratio Change ◽  
Vertical Walls ◽  
Energy Equations

In this study, the mixed convective heat transfer in a lid-driven cavity was investigated numerically. The finite volume discritization method was used to solve the momentum and energy equations by using the classic Boussinesq incompressible approximation. The cavity vertical walls are insulated whereas the bottom (hot wall) and top (cold wall) surface are maintained at a uniform temperature and fins are located on bottom wall. The effect of fin numbers over the flow field and heat transfer was investigated at various Richardson numbers. Study was carried out for Richardson numbers ranging from 0.01 to 10, fin numbers between 1 and 7, fin height ratio change from 0.05 to 0.3, and thermal conductivity ratio (fin to fluid) from 10 to 104, respectively. The results are presented in the form of streamlines, temperature contours, and Nusselt number distributions. The results show that the Nusselt number increases when the number of fin and fin height decrease. In addition, in all cases an increasing Richardson number caused increasing the relative Nusselt number ( Nu / Nu0). The heat transfer enhancement was observed at low fin numbers (1 and 3) and high Richardson number in comparison with the cavity without fins.

scholarly journals Buoyancy heat transfer in staggered dividing square enclosure

2011 ◽  
Vol 15 (2) ◽  
pp. 409-422 ◽  
Author(s):  
Viktor Terekhov ◽  
Alexander Chichindaev ◽  
Ali Ekaid
Keyword(s):  
Heat Transfer ◽  
Heat Conductivity ◽  
Fluid Motion ◽  
Average Heat Transfer Coefficient ◽  
Heat Conductivity Coefficient ◽  
Square Cavity ◽  
Average Heat ◽  
Square Enclosure ◽  
Different Temperatures ◽  
Vertical Walls

This study represents the results of numerical simulation of fluid motion and free-convective heat transfer in a square cavity with partitions mounted on the lower (heated) and upper (cooled) walls. The height of partitions and their heat conductivity were varied Kr = 2 ? 8000 together with Rayleigh number Ra = 103 ? 106, which corresponded to the laminar flow. It is assumed that vertical walls of the cavity are adiabatic, and its horizontal walls are kept at constant, but different temperatures. The numerical solution based on transformation of determining equations by the method of finite differences was achieved. The obtained results show that the surface-average heat transfer coefficient decreases with a rise of partition height due to the suppression of convection. Also the results show that with an increase in heat conductivity coefficient of partitions, the Nusselt number increases significantly. In addition, it was found that when the value of relative heat conductivity coefficient changes by four orders, Nu number for the highest partitions changes by the factor of 1.5 - 2 only and integral heat transfer through the whole interlayer increases with development of the heat exchanging area.

A NUMERICAL STUDY OF FREE CONVECTIVE HEAT TRANSFER FROM A HEATED HALF-CYLINDER IN AN ENCLOSURE

1995 ◽  
Vol 19 (3) ◽  
pp. 285-300
Author(s):  
P.H. Oosthuizen ◽  
J.T. Paul
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Boussinesq Approximation ◽  
Approximate Model ◽  
Governing Equations ◽  
Free Convective Flow ◽  
Wide Range ◽  
Fluid Properties ◽  
Different Temperatures ◽  
Side Walls

Two-dimensional free convective flow in an enclosure which has a heated half-cylinder on the floor has been numerically studied. The half-cylinder is kept at a uniform high temperature. The enclosure has horizontal upper and lower walls and inclined side-walls. The side-walls are also kept at uniform temperatures and the top and bottom surfaces are adiabatic. In general, the side-walls have been assumed to be at different temperatures. The situation considered is an approximate model of that which occurs in some simple crop dryers. The flow has been assumed to be steady and laminar. Fluid properties have been assumed constant except for the density change with temperature which has been treated using the Boussinesq approximation. The governing equations have been written in dimensionless form and solved using a finite element method. Results have been obtained for a wide range of the governing parameters for a Prandtl number of 0.7, i.e. for air, and the effects of these governing parameters on the heat transfer rate has been studied.

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.

Convective Heat Transfer in a Rectangular Porous Cavity—Effect of Aspect Ratio on Flow Structure and Heat Transfer

1984 ◽  
Vol 106 (1) ◽  
pp. 158-165 ◽  
Author(s):  
V. Prasad ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Aspect Ratios ◽  
Family Of Curves ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Rayleigh Numbers ◽  
Cavity Effect ◽  
Cavity Width

Two-dimensional steady natural convection in a porous rectangular cavity bounded by isothermal vertical walls at different temperatures and adiabatic horizontal walls has been studied numerically for aspect ratios less than unity and Rayleigh numbers up to 104. Results indicate the presence of multicellular flow. Also, the average Nusselt number based on cavity width is observed to be a maximum in a restricted range of aspect ratio, depending on the Rayleigh number. Effects of aspect ratio are summarized by a family of curves for constant Rayleigh number, based on cavity height, for aspect ratios from 0.05 to 100. For a cavity with fixed height, the heat transfer rate always increases as the aspect ratio is increased, except when the flow exhibits boundary layers on the vertical walls. Criteria in terms of aspect ratio and Rayleigh number have been established for the existence of different flow regimes.

scholarly journals Effect of Variable Thermal Conductivity on Buoyant Convection in a Cavity with Internal Heat Generation

2007 ◽  
Vol 12 (1) ◽  
pp. 113-122 ◽  
Author(s):  
S. Sivasankaran
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Numerical Study ◽  
Internal Heat ◽  
Variable Thermal Conductivity ◽  
Governing Equations ◽  
Heat Transfer Characteristics ◽  
Square Cavity ◽  
Thermal Conductivity Parameter ◽  
Conductivity Parameter

A numerical study has been made to analyze the effects of variable thermal conductivity on the natural convection of heat generating fluids contained in a square cavity with isothermal walls and the top and bottom perfectly insulated surfaces. The flow is assumed to be two-dimensional. Calculations are carried out by solving governing equations for different parameters. The flow pattern and the heat transfer characteristics inside the cavity are presented in the form of steady-state streamlines, isotherms and velocity profiles. The heat transfer rate is increased by an increase in the thermal conductivity parameter.

Sign in / Sign up

Export Citation Format

Share Document