scholarly journals Numerical Investigation of Natural Convection and Surface Radiation in an Air Filled Square Enclosure with a Wavy Bottom Wall

2018 ◽  
Vol 18 (3) ◽  
pp. 1137-1148
Author(s):  
Mesut Tekkalmaz
Keyword(s):  
Natural Convection ◽  
Numerical Investigation ◽  
Surface Radiation ◽  
Bottom Wall ◽  
Square Enclosure

Effect of Surface Radiation on Multiple Natural Convection Solutions in a Square Cavity Partially Heated from Below

2006 ◽  
Vol 128 (10) ◽  
pp. 1012-1021 ◽  
Author(s):  
El Hassan Ridouane ◽  
Mohammed Hasnaoui
Keyword(s):  
Steady State ◽  
Natural Convection ◽  
Numerical Study ◽  
Heated Surface ◽  
Steady State Solution ◽  
Surface Radiation ◽  
Bottom Wall ◽  
Square Cavity ◽  
Square Enclosure ◽  
Surface Dimension

A numerical study of natural convection with surface radiation in an air filled square enclosure with a centrally heated bottom wall and cooled upper wall is presented. The vertical walls and the rest of the bottom wall are assumed to be insulated. The problem is studied for Rayleigh numbers Ra, ranging from 103 to 4×106 and surfaces emissivity ε, varying from 0 to 1. The governing equations, written in terms of stream function-vorticity formulation, are solved using a finite difference approach. It is found that, under these heating/cooling conditions, three different steady-state solutions are possible in the ranges of the parameters considered. Results are presented detailing the occurrence of each steady-state solution and the effect of Ra and ε on its range of existence. It is found that the surface radiation alters significantly the existence ranges of the solutions. For each solution, convective and radiative contributions to the global heat transfer are also quantified for various Ra and ε. The influence of the heated surface dimension on the fluid flow and thermal patterns is also presented by comparing the present results against those obtained by the authors in an earlier study within a square cavity totally heated from below.

Experimental and Numerical Investigation on Natural Convection Heat Transfer of TiO2–Water Nanofluids in a Square Enclosure

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Yanwei Hu ◽  
Yurong He ◽  
Shufu Wang ◽  
Qizhi Wang ◽  
H. Inaki Schlaberg
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Numerical Investigation ◽  
Convection Heat Transfer ◽  
Distribution Functions ◽  
Lattice Boltzmann Model ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Square Enclosure

An experimental and numerical investigation on natural convection heat transfer of TiO2–water nanofluids in a square enclosure was carried out for the present work. TiO2–water nanofluids with different nanoparticle mass fractions were prepared for the experiment and physical properties of the nanofluids including thermal conductivity and viscosity were measured. Results show that both thermal conductivity and viscosity increase when increasing the mass fraction of TiO2 nanoparticles. In addition, the thermal conductivity of nanofluids increases, while the viscosity of nanofluids decreases with increasing the temperature. Nusselt numbers under different Rayleigh numbers were obtained from experimental data. Experimental results show that natural convection heat transfer of nanofluids is no better than water and even worse when the Rayleigh number is low. Numerical studies are carried out by a Lattice Boltzmann model (LBM) coupling the density and the temperature distribution functions to simulate the convection heat transfer in the enclosure. The experimental and numerical results are compared with each other finding a good match in this investigation, and the results indicate that natural convection heat transfer of TiO2–water nanofluids is more sensitive to viscosity than to thermal conductivity.

Numerical Investigation of Natural Convection in a Square Enclosure with a Baffle Mounted on Vertical Wall

2015 ◽  
Vol 813-814 ◽  
pp. 748-753 ◽  
Author(s):  
N. Nagasubramanian ◽  
M.R. Thansekhar ◽  
M. Venkatesan ◽  
K. Ramanathan
Keyword(s):  
Natural Convection ◽  
Numerical Investigation ◽  
Average Nusselt Number ◽  
Vertical Wall ◽  
Temperature Fields ◽  
Cold Wall ◽  
Primary Vortex ◽  
Square Enclosure ◽  
Flow And Heat Transfer ◽  
Laminar Natural Convection

Results from numerical investigation of laminar natural convection inside a differentially heated square enclosure with a thin baffle attached to the cold wall are reported. The effect of the baffles on the flow and temperature fields were analyzed for baffle lengths equal to 20, 35 and 50 percent of the width of the enclosure, attached at three locations for Ra = 104, 105, 106 and Pr = 0.707. The presence of a baffle on the cold right wall affects the strength of the clockwise rotating primary vortex. Reduced flow and heat transfer are observed. Longer the baffle more pronounced the effect on the flow field. Secondary convection cells are seen between the baffle and the bottom wall for certain cases. Reduction in average Nusselt Number is observed on the cold wall with the baffle than the hot wall.

Numerical computation of natural convection inside a curved-shape nanofluid-filled enclosure with nonuniform heating of the bottom wall

2019 ◽  
Vol 30 (01) ◽  
pp. 1950006 ◽  
Author(s):  
Abdellaziz Yahiaoui ◽  
Mahfoud Djezzar ◽  
Hassane Naji
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Pure Water ◽  
Bottom Wall ◽  
Working Fluid ◽  
Nonuniform Heating ◽  
Square Enclosure ◽  
Nusselt Numbers

This paper performs a numerical analysis of the natural convection within two-dimensional enclosures (square enclosure and enclosures with curved walls) full of a H2O-Cu nanofluid. While their vertical walls are isothermal with a cold temperature [Formula: see text], the horizontal top wall is adiabatic and the bottom wall is kept at a sinusoidal hot temperature. The working fluid is assumed to be Newtonian and incompressible. Three values of the Rayleigh number were considered, viz., 103, 104, 105, the Prandtl number is fixed at 6.2, and the volume fraction [Formula: see text] is taken equal to 0% (pure water), 10% and 20%. The numerical simulation is achieved using a 2D-in-house CFD code based on the governing equations formulated in bipolar coordinates and translated algebraically via the finite volume method. Numerical results are presented in terms of streamlines, isotherms and local and average Nusselt numbers. These show that the heat transfer rate increases with both the volume fraction and the Rayleigh number, and that the average number of Nusselt characterizing the heat transfer raises with the nanoparticles volume fraction.

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