A complete heatline analysis on mixed convection within a square cavity: Effects of thermal boundary conditions via thermal aspect ratio

2012 ◽  
Vol 57 ◽  
pp. 98-111 ◽  
Author(s):  
D. Ramakrishna ◽  
Tanmay Basak ◽  
S. Roy ◽  
I. Pop
Keyword(s):  
Aspect Ratio ◽  
Boundary Conditions ◽  
Mixed Convection ◽  
Square Cavity ◽  
Thermal Boundary Conditions ◽  
Cavity Effects

Effects of Thermal Boundary Conditions on Entropy Generation During Natural Convection in a Differentially Heated Square Cavity

2010 ◽  
Author(s):  
Ram Satish Kaluri ◽  
Tanmay Basak ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Boundary Conditions ◽  
Entropy Generation ◽  
Bottom Wall ◽  
Convection Flow ◽  
Uniform Heating ◽  
Square Cavity ◽  
Fluid Friction ◽  
Thermal Boundary Conditions

Natural convection is a widely occurring phenomena which has important applications in material processing, energy storage devices, electronic cooling, building ventilation etc. The concept of ‘entropy generation minimization’, which is a thermodynamic approach for optimization, may be very useful in designing efficient thermal systems. In the current study, entropy generation in steady laminar natural convection flow in a square cavity is studied with following isothermal boundary conditions: (1) Bottom wall is uniformly heated (2) Bottom wall is sinusoidally heated. The side walls are maintained cold and the top wall is maintained adiabatic. The thermal boundary condition in non-uniform heating case (case 2) is such that the dimensionless average temperature of the bottom wall is equal to that of uniform heating case (case 1). The prime objective of this work is to investigate the influence of uniform and non-uniform heating on entropy generation. The governing mass, momentum and energy equations are solved using Galerkin finite element method. Streamlines, isotherms, contour maps of entropy generation due to heat transfer and fluid friction are studied for Pr = 0.01 (molten metals) and 7 (water) in range of Ra = 103–105. Detailed analysis on the effect of uniform and non-uniform thermal boundary conditions on entropy generation due to heat transfer and fluid friction has been presented. Also, the average Bejan’s number which indicates the relative dominance of entropy generation due to heat transfer or fluid friction and the total entropy generation are studied for each case.

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.

Pseudo 3D modeling of suction and injection effects on fully developed laminar flow and heat transfer in rectangular fuel cell channels

2017 ◽  
Vol 232 (3) ◽  
pp. 266-281
Author(s):  
A Doosti Abukheyli ◽  
H Hassanzadeh ◽  
SA Mirbozorgi
Keyword(s):  
Fuel Cell ◽  
Aspect Ratio ◽  
Boundary Conditions ◽  
Rectangular Channel ◽  
Numerical Results ◽  
Wall Friction ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Energy Equations

In this paper, the flow in the rectangular fuel cell channel with different aspect ratios has been numerically simulated. The bottom wall of the rectangular channel is porous and subjected to a uniform mass injection or suction, while the other three walls are nonporous or impermeable. Assuming the hydro-dynamically and thermally fully developed flow, the mass, momentum, and energy equations have been solved with a two-dimensional code. The present numerical results are in good agreement with the numerical results in the literature. The wall friction coefficients and Nusselt numbers were obtained for different aspect ratios, different wall Reynolds numbers (for suction and injection), and different thermal boundary conditions. The results show that for each aspect ratio, friction coefficient ( fRe) is larger for injection than for suction. Also at unit expect ratio, a/ b = 1, the fRe have minimum value for each wall Reynolds number ( Rem) and with increasing and decreasing aspect ratio, fRe increases. The changes of Nusselt ( Nu) number with Rem and aspect ratio is dependent on the thermal boundary conditions and definition of Nu number (for combined boundary condition).

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