Natural Convection Reduction in a Composite Air/Porous Annular Region With Horizontal Orientation

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
M. Ait saada ◽  
S. Chikh ◽  
A. Campo
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Porous Material ◽  
Thermal Insulation ◽  
Control Volume ◽  
Outer Cylinder ◽  
Convection Heat Transfer ◽  
Flow In Porous Media ◽  
Temperature Fields ◽  
Annular Region

This paper deals with a numerical investigation on natural convection heat transfer in a long horizontal annular region formed with a heated inner cylinder and a cooled outer cylinder. Identifying the annular region geometrically by its radius ratio, it is divided into two subregions: a thicker outer subregion is filled with a porous material saturated by air, whereas a thinner inner subregion is clear. Based on the general Darcy–Brinkman–Forchheimer model for flow in porous media, numerical calculations with the control volume method produce the velocity and temperature fields of the air motion in the two subregions. The baseline case corresponds to an annular region of same dimensions, but filled completely with a porous material saturated by air. Upon articulating the physical properties of a porous material with the clear gap size, the analyst will be able to tune those conditions that are conducive to heat transfer reduction across the concentric two-cylinder configuration. The outcome of this paper is equivalent to the determination of superior thermal insulation performance using lesser porous material. In other words, this paper boils down to beneficial energy conservation together with money savings in the purchase of the thermal insulation.

scholarly journals Natural convection heat transfer in a partially divided trapezoidal enclosure

2009 ◽  
Vol 13 (4) ◽  
pp. 213-220 ◽  
Author(s):  
Mehmet Arici ◽  
Birol Şahin
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Control Volume ◽  
Convection Heat Transfer ◽  
Temperature Fields ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Flow Strength ◽  
Uniform Temperature Field ◽  
Trapezoidal Enclosure

Natural convection heat transfer in a partially divided trapezoidal enclosure is studied numerically using the control volume method. Summer and winter conditions are separately examined by imposing regarding thermal boundary conditions. A horizontal divider included and its two different placements are considered. It is shown that heat transfer results are not significantly altered by the presence of the divider for summer condition. For winter condition, on the other hand, decrement in heat loss and effect on the flow and the temperature fields by the presence and the placement of the divider are observed, respectively. As a horizontal divider is placed to oppose buoyancy, the flow strength becomes weaker and formation of two separate levels of temperature uniformity occurs. As the divider is placed to assist buoyancy, the flow gets stronger and tends to form relatively uniform temperature field within whole enclosure.

scholarly journals Prediction of Natural Convection Heat Transfer Phenomena of Nanofluids in Corrugated Annulus

2020 ◽  
Author(s):  
Sattar Aljobair ◽  
Akeel Abdullah Mohammed ◽  
Israa Alesbe
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Outer Cylinder ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat

Abstract The natural convection heat transfer and fluid flow characteristic of water based Al2O3 nano-fluids in a symmetrical and unsymmetrical corrugated annulus enclosure has been studied numerically using CFD. The inner cylinder is heated isothermally while the outer cylinder is kept constant cold temperature. The study includes eight models of corrugated annulus enclosure with constant aspect ratio of 1.5. The governing equations of fluid motion and heat transfer are solved using stream-vorticity formulation in curvilinear coordinates. The range of solid volume fractions of nanoparticles extends from PHI=0 to 0.25, and Rayleigh number varies from 104 to 107. Streamlines, isotherms, local and average Nusselt number of inner and outer cylinder has been investigated in this study. Sixty-four correlations have been deduced for the average Nusselt number for the inner and outer cylinders as a function of Rayleigh number have been deduced for eight models and five values of volume fraction of nano particles with an accuracy range 6-12 %. The results show that, the average heat transfer rate increases significantly as particle volume fraction and Rayleigh number increase. Also, increase the number of undulations in unsymmetrical annuli reduces the heat transfer rates which remain higher than that in symmetrical annuli. There is no remarkable change in isotherms contour with increase of volume fraction of nanofluid.

Natural Convection in a Nano-Fluid Filled Square Enclosure

2020 ◽  
Vol 847 ◽  
pp. 114-119
Author(s):  
Barbie Leena Barhoi ◽  
Ramesh Chandra Borah ◽  
Sandeep Singh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Control Volume ◽  
Convection Heat Transfer ◽  
Ansys Fluent ◽  
Square Enclosure ◽  
Nano Fluid

The present study relates to numerical investigation of natural convection heat transfer in a nanofluid filled square enclosure. One side of the enclosure is maintained at high temperature and the other side at a low temperature; while the top and bottom sides are adiabatic. The commercial CFD software ANSYS-FLUENT© was used to solve this numerical problem with the governing differential equations discretized by a control volume approach. nanofluids of Cu-water, Al2O3-water and TiO2-water have been simulated for a range of Rayleigh numbers and volume fractions. The results were obtained in the form of streamlines and isotherms. Interpretations of the results are done based on heat transfer rates, volume fraction, Rayleigh number and Nusselt number. It is to be noted that addition of nanoparticles enhances the heat transfer rate. It is also observed that the Nusselt number is highly affected by volume fraction and Rayleigh number.

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