Natural Convection in Rectangular Cavities at Various Aspect Ratios and Inclinations With Isothermal Sidewalls and Constant Flux Heat Source on the Bottom Wall

2004 ◽  
Author(s):  
M. A. R. Sharif ◽  
Taqui-ur-Rahman Mohammed
Keyword(s):  
Natural Convection ◽  
Heat Source ◽  
Heat Transfer Process ◽  
Bottom Wall ◽  
Maximum Temperature ◽  
Bottom Surface ◽  
Source Surface ◽  
Constant Flux ◽  
Aspect Ratios ◽  
Inclination Angles

Natural convection in rectangular cavities is studied numerically using a finite volume based computational procedure. In many applications, especially for cooling of electronic components, a natural convection configuration is encountered where the heat source is at the bottom surface and the sidewalls are at colder temperature while the top wall can be considered adiabatic. The present study is based on such a configuration where a constant flux heat source is symmetrically embedded at the bottom wall. The non-heated parts of the bottom wall are considered adiabatic. The study includes computations for cavities at various aspect ratios, ranging from 0.5 to 2, and inclination angles of the cavity from 0° to 30°. The Grashof number is varied from 103 to 106. The effects of aspect ratio and inclination angles on the heat transfer process are analysed. Results are presented in the form of streamline and isotherm plots as well as the variation of the average Nusselt number and maximum temperature at the heat source surface under different conditions.

scholarly journals A Numerical Study of Mixed Convection in Square Lid-Driven with Internal Elliptic Body and Constant Flux Heat Source on the Bottom Wall

2017 ◽  
Vol 9 (2) ◽  
pp. 145-158 ◽  
Author(s):  
M. J. H. Munshi ◽  
M. A. Alim ◽  
M. Ali ◽  
M. S. Alam
Keyword(s):  
Heat Source ◽  
Mixed Convection ◽  
Richardson Number ◽  
Numerical Study ◽  
Bottom Wall ◽  
Maximum Temperature ◽  
Source Surface ◽  
Constant Flux ◽  
Moving Wall ◽  
The Magnetic Field

The mixed convection in square lid-driven with internal elliptic body and constant flux heat source on the bottom wall is numerically simulated in this paper following a finite element method approach. The left moving wall and right moving wall are cold. The upper wall is insulated and so is the lower wall with heat flux located in the middle. The magnetic field of strength B is applied parallel to x- axis. Result is presented for different Richardson numbers (0.01 ? Ri ? 10) when Grashof numbers are (10 ? Gr ? 50) and Prandtl number is taken as Pr = 0.733 for all computations. The influence of the Richardson number on heat source surface is being investigated in this paper. Results are presented in the form of streamline and isotherm plots as well as the variation of the maximum temperature and Nusselt number at the heat source surface under different conditions. A detailed analysis of flow pattern shows that the mixed convection is based on the parameters Richardson number (Ri), Grashof number (Gr) and Reynolds number (Re).

Effect of the Temperature Difference Aspect Ratio on Natural Convection in a Square Cavity for Nonuniform Thermal Boundary Conditions

2007 ◽  
Vol 129 (12) ◽  
pp. 1723-1728 ◽  
Author(s):  
M. Sathiyamoorthy ◽  
Tanmay Basak ◽  
S. Roy ◽  
N. C. Mahanti
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Temperature Difference ◽  
Heat Transfer Process ◽  
Bottom Wall ◽  
Maximum Temperature ◽  
Convection Flow ◽  
Square Cavity ◽  
Thermal Boundary Conditions

The present numerical investigation deals with steady natural convection flow in a closed square cavity when the bottom wall is sinusoidal heated and vertical walls are linearly heated, whereas the top wall is well insulated. In the nonuniformly heated bottom wall maximum temperature TH attains at the center of the bottom wall. The sidewalls are linearly heated, maintained at minimum temperature Tc at top edges of the sidewalls and at temperature Th at the bottom edges of the sidewalls, i.e., Tc≤Th≤TH. Nonlinear coupled PDEs governing the flow have been solved by the penalty finite element method with biquadratic rectangular elements. Numerical results are obtained for various values of Prandtl number (Pr)(0.01≤Pr≤10) and temperature difference aspect ratio A=[(Th−Tc)∕(TH−Tc)](0≤A≤1) for higher Raleigh number Ra=105. Results are presented in the form of streamlines, isotherm contours, local Nusselt number, and the average Nusselt number as a function of temperature difference aspect ratio A. The overall heat transfer process is shown to be tuned efficiently with suitable selection of A.

scholarly journals Natural convection in tilted square cavities with triangular shaped top cold wall

1970 ◽  
Vol 39 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Tamanna Sultana ◽  
Sumon Saha ◽  
Goutam Saha ◽  
Md Quamrul Islam
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Nusselt Number ◽  
Natural Convection ◽  
Numerical Study ◽  
Constant Heat Flux ◽  
Heat Transfer Process ◽  
Bottom Wall ◽  
Grashof Number ◽  
Inclination Angles

A numerical study of natural convection in a tilted square cavity with heated horizontal base and cold upper wall is presented. The present study is based in such a configuration where the top triangular wall of two different shapes is maintained at a constant low temperature. A constant heat flux source whose length is 20% of the total length of the cavity is discretely embedded at the left corner of the bottom wall. The remaining part of the bottom wall and the two sidewalls are considered to be adiabatic. The study includes computations for inclination angles of the cavity from 0° to 45°, where the Grashof number, Gr varies from 103 to 106. The Penalty finite element method has been used to see the effects of inclination angles and Grashof number on heat transfer process in the cavity. Results are presented in the form of streamline and isotherm plots as well as the variation of the average Nusselt number. Observation shows the significant effect of different triangular top surface on the heat transfer characteristics at the higher Grashof number and inclination angle. Keywords: Natural convection, Penalty finite element, Nusselt number, Isoflux heating. doi:10.3329/jme.v39i1.1831 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 30-39  

scholarly journals Heat Transfer Performance of Different Fluids During Natural Convection in Enclosures with Varying Aspect Ratios

2021 ◽  
Vol 287 ◽  
pp. 03010
Author(s):  
Rajashekhar Pendyala ◽  
Suhaib Umer Ilyas ◽  
Yean Sang Wong
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Natural Convection Heat Transfer ◽  
Transfer Performance ◽  
Convection Heat ◽  
Aspect Ratios

The heat transfer process takes place in numerous applications through the natural convection of fluids. Investigations of the natural convection heat transfer in enclosures have gained vital importance in the last decade for the improvement in thermal performance and design of the heating/cooling systems. Aspect ratios (AR=height/length) of the enclosures are one of the crucial factors during the natural convection heat transfer process. The investigated fluids consisting of air, water, engine oil, mercury, and glycerine have numerous engineering applications. Heat transfer and fluid flow characteristics are studied in 3-dimensional rectangular enclosures with varying aspect ratios (0.125 to 150) using computational fluid dynamics (CFD) simulations. Studies are carried out using the five different fluids having Prandtl number range 0.01 to 4500 in rectangular enclosures with the hot and cold surface with varying temperature difference 20K to 100K. The Nusselt number and heat transfer coefficients are estimated at all conditions to understand the dependency of ARs on the heat transfer performance of selected fluids. Temperature and velocity profiles are compared to study the flow pattern of different fluids during natural convection. The Nusselt number correlations are developed in terms of aspect ratio and Rayleigh number to signify the natural convection heat transfer performance.

A Comparison of the Relative Effectiveness of Fin Aspect Ratio Under Natural Convective Heat Transfer With Top Mounted Fins

2009 ◽  
Author(s):  
Anthony S. Pruszenski
Keyword(s):  
Natural Convection ◽  
Aspect Ratio ◽  
Heat Load ◽  
Relative Effectiveness ◽  
Internal Heat ◽  
Maximum Temperature ◽  
Constant Heat ◽  
Aspect Ratios ◽  
Square Plate ◽  
Base Width

Mechanical engineers often design fins on metal enclosures to dissipate an internal heat load using natural convection. This paper gives the results of a series of CFD (Computational Fluid Dynamics) studies, and, supporting calculations for the maximum temperature rise on a plate with a constant heat load of 100 watts applied to the bottom of the plate. Vertical fins are formed on the top surface of the plate. In this study, the horizontal dimensions and thickness of a square plate are held constant, while, the aspect ratio of the top surface fins are varied between studies. The aspect ratio is defined as the ratio of the height of the fin to the width of the base of the fin. The study compares aspect ratios from 1:1 to 40:1 with a constant base width. In addition, comparisons between 20:1 aspect ratio fins with the same height but with different fin counts due to changes in fin separation distances are compared. Closely spaced fins are not always the best solution for natural convection.

scholarly journals Effect of Heat Source Placement on Natural Convection from Cylindrical Surfaces

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4334
Author(s):  
Andrej Kapjor ◽  
Peter Durcansky ◽  
Martin Vantuch
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Theoretical Models ◽  
Heat Transfer Process ◽  
Heat Output ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Thermal Fields ◽  
Horizontal Cylinders

Placement of heat source can play a significant role in final heat output, or heat source effectivity. Because of this, there is a need to analyze thermal fields of the heat exchange system by natural convection, where the description by criterion equations is desired, as the net heat output from tubes can be quantified. Based on known theoretical models, numerical methods were adapted to calculate the heat output with natural air flow around tubes, where mathematical models were used to describe the heat transfer more precisely. After validation of heat transfer coefficients, the effect of wall and heat source placement was studied, and the Coanda effect was also observed. The heat source placement also has an effect at the boundary layer, which can change and therefore affect the overall heat transfer process. The optimal wall-to-cylinder distance for an array of horizontal cylinders near a wall was also expressed as a function of the Rayleigh number and number of cylinders in the array.

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