Analysis of the Time-Dependent Heating on the Natural Convection from a Vertical Open Ended Porous Cylinder

2008 ◽  
Vol 273-276 ◽  
pp. 28-33 ◽  
Author(s):  
Djamel Eddine Ameziani ◽  
K. Bouhadef ◽  
Rachid Bennacer
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Wall Temperature ◽  
Flow Model ◽  
Convection Heat Transfer ◽  
Lateral Wall ◽  
Natural Convection Heat Transfer ◽  
Porous Cylinder ◽  
Constant Wall Temperature ◽  
Unsteady Natural Convection

The problem of unsteady natural convection heat transfer in a vertical opened porous cylinder submitted to a sinusoidal time variation temperature on the lateral wall has been investigated numerically. The widely used Darcy flow model without flow establishment at the cylinder exit has been used. In the case of constant wall temperature, two types of flows were obtained, with and without fluid recirculation, depending on the filtration Rayleigh number (Ra), the aspect ratio (A) and the Biot number (Bi) have been obtained. The obtained heat transfer, in case of low dimensionless oscillations amplitude (XA<0.5), shows a non significant enhancement (less than 5%) in comparison to the constant wall temperature case.

Pseudo-Steady-State Natural Convection Heat Transfer Inside a Vertical Cylinder

1986 ◽  
Vol 108 (2) ◽  
pp. 310-316 ◽  
Author(s):  
Y. S. Lin ◽  
R. G. Akins
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Vertical Cylinder ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Constant Wall Temperature ◽  
Stream Functions

The SIMPLER numerical method was used to calculate the pseudo-steady-state natural convection heat transfer to a fluid inside a closed vertical cylinder for which the boundary temperature was spatially uniform and the temperatures throughout the entire system were increasing at the same rate. (Pseudo-steady state is comparable to the steady-state problem for a fluid with uniform heat generation and constant wall temperature.) Stream functions, temperature contours, axial velocities, and temperature profiles are presented. The range of calculation was 0.25 < H/D < 2, Ra < 107, and Pr = 7. This range includes conduction to weak turbulence. A characteristic length defined as 6 × (volume)/(surface area) was used since it seemed to produce good regression results. The overall heat transfer for the convection-dominated range was found to be correlated by Nu = 0.519 Ra0.255, where the temperature difference for both the Nusselt and Rayleigh numbers was the center temperature minus the wall temperature. Correlations using other temperature differences are also presented for estimating the volumetric mean and minimum temperatures.

Effect of spatial side-wall temperature variation on transient natural convection of a nanofluid in a trapezoidal cavity

2017 ◽  
Vol 27 (6) ◽  
pp. 1365-1384 ◽  
Author(s):  
Ammar I. Alsabery ◽  
Ishak Hashim ◽  
Ali J. Chamkha ◽  
Habibis Saleh ◽  
Bilal Chanane
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Temperature Variation ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Side Wall ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Content Type ◽  
Transient Natural Convection

Purpose This paper aims to study analytically and numerically the problem of transient natural convection heat transfer in a trapezoidal cavity with spatial side-wall temperature variation. Design/methodology/approach The governing equations subject to the initial and boundary conditions are solved numerically by the finite difference scheme consisting of the alternating direction implicit method and the tri-diagonal matrix algorithm. The left sloping wall of the cavity is heated to non-uniform temperature, and the right sloping wall is maintained at a constant cold temperature, while the horizontal walls are kept adiabatic. Findings It is shown that the heat transfer rate increases in non-uniform heating increments, whereby low wave number values are more affected by the convection. The best heat transfer enhancement results from larger side wall inclination angle; however, trapezoidal cavities require longer time compared to that of square to reach steady state. Originality/value The study of natural convection heat transfer in a trapezoidal cavity filled with nanofluid and heated by spatial side-wall temperature has not yet been undertaken. Thus, the authors of the present study believe that this work is valuable.

Effects of Heat Intensity, Size, and Position of the Components on Temperature Distribution Within an Electronic PCB Enclosure

1990 ◽  
Vol 112 (3) ◽  
pp. 249-254 ◽  
Author(s):  
Z.-G. Du ◽  
E. Bilgen
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Temperature Distribution ◽  
Laminar Flow ◽  
Flow Model ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Two Dimensional ◽  
Convection Heat ◽  
Laminar Flow Model

Natural convection heat transfer has been studied in a sealed small PCB enclosure of three heated components which are mounted on a PCB plate within a large console cooled by vented airflow. A two-dimensional laminar flow model is used with appropriate boundary conditions. Detailed influences of each parameter, such as intensity, size, and position of the heaters on temperature and flow distributions within the enclosure have been studied. The favorable component arrangements for various cases have been determined.

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