An experimental investigation on natural convection of non-covalently functionalized MWCNTs nanofluids: Effects of aspect ratio and inclination angle

In this paper, a series of numerical simulations for natural convection of water near its maximum-density around a cylinder inside a concentric triangular enclosure were conducted using finite volume method. The effects of the density inversion parameter, the aspect ratio, the Rayleigh number and the inclination angle on natural convection were discussed. Furthermore, the flow and temperature fields, the local and average Nusselt numbers at different parameters were obtained and analyzed. The results show that the flow pattern and temperature distribution are unique for various density inversion parameters and inclination angles. The density inversion parameter, the aspect ratio, the Rayleigh number all have significant effects on the overall heat transfer rates, except for the inclination angle. The present results can also contribute further information on the natural convection of non-Boussinesq fluid in enclosures.

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Experimental Investigation on the Effect of Longitudinal Aspect Ratio on Natural Convection in Inclined Channels Heated Below

Volume 4: Fatigue and Fracture, Heat Transfer, Internal Combustion Engines, Manufacturing, and Technology and Society ◽

10.1115/esda2006-95526 ◽

2006 ◽

Author(s):

Assunta Andreozzi ◽

Bernardo Buonomo ◽

Oronzio Manca ◽

Sergio Nardini

Keyword(s):

Heat Flux ◽

Experimental Investigation ◽

Natural Convection ◽

Flow Visualization ◽

Inclination Angle ◽

Flow Separation ◽

Heated Wall ◽

Uniform Heat Flux ◽

Heated Plate ◽

Inclined Channels

In this paper an experimental investigation on natural convection in air in inclined channels with rectangular transversal section and lower wall heated at uniform heat flux is carried out. Wall temperature measurements and flow visualization are presented. The results allow investigating on the effect of the distance between the two principal parallel walls and of the inclination angle. The experiments are accomplished for two channel gap values: 20 and 40 mm. The inclination angle is equal to 80° and 88°. The flow development and the shape of flow transitions along the channel are visualized. Flow visualization allows to describe the secondary motion inside an inclined channel. Flow separation region along the lower heated plate begins at lower axial coordinate as the wall heat flux, the inclination angle and the channel gap are greater. The flow separation depends also on transversal coordinate. The detected secondary structures pass from thermals to plumes and vortices. Along the plane parallel to the heated wall, the visualization shows that thermal plumes split in V-shaped structures. For the largest considered channel gap value the instability phenomena in the channel are stronger and chaotic motion in the channel outlet zone is observed. When the channel gap value increases wall temperatures become lower because the higher distance between the walls determines a greater mass flow rate and an increase in the heat transfer.

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Experimental Investigation of Natural Convection in an Asymmetrically Heated Vertical Channel with an Asymmetric Chimney

Journal of Heat Transfer ◽

10.1115/1.1928909 ◽

2005 ◽

Vol 127 (8) ◽

pp. 888-896 ◽

Cited By ~ 12

Author(s):

Oronzio Manca ◽

Marilena Musto ◽

Vincenzo Naso

Keyword(s):

Heat Flux ◽

Experimental Investigation ◽

Natural Convection ◽

Aspect Ratio ◽

Vertical Channel ◽

Expansion Ratio ◽

Uniform Heat Flux ◽

Geometrical Parameters ◽

Nusselt Numbers ◽

Lower Maximum

An experimental investigation on air natural convection, in a vertical channel asymmetrically heated at uniform heat flux, with downstream unheated parallel extensions, is carried out. One extension is coplanar to the unheated channel wall and the distance between the extensions is equal to or greater than the channel gap (geometrically asymmetric chimney). Experiments are performed with different values of the wall heat flux, aspect ratio (Lh∕b), extension ratio (L∕Lh) and expansion ratio (B∕b). For the largest value of the aspect ratio (Lh∕b=10), the adiabatic extensions improve the thermal performance in terms of lower maximum wall temperature of the channel. Optimal configurations of the system with asymmetrical chimney are detected. Flow visualization shows a cold inflow in the channel-chimney system that penetrates down below the channel exit section. Maximum wall temperatures and channel Nusselt numbers are correlated to the channel Rayleigh number, Ra*, and to the geometrical parameters, in the ranges 3.0×102⩽Ra*B∕b⩽1.0105, 1.0⩽B∕b⩽3.0 and 1.0⩽L∕Lh⩽4.0 with Lh∕b=5.0 and 10.0.

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Enhancement of natural convection heat transfer in concentric annular space using inclined elliptical cylinder

Journal of Naval Architecture and Marine Engineering ◽

10.3329/jname.v17i2.44991 ◽

2020 ◽

Vol 17 (2) ◽

pp. 89-99

Author(s):

Houssem Laidoudi

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Aspect Ratio ◽

Heat Transfer Rate ◽

Inclination Angle ◽

Transfer Rate ◽

Convection Heat Transfer ◽

Natural Convection Heat Transfer ◽

Convection Heat ◽

Elliptical Cross

The governing equations of continuity, momentum and energy are numerically solved to study the laminar natural convection heat transfer of Newtonian fluid confined within two concentric cylinders. The inner cylinder is elliptical cross-section with different aspect ratio E = 0.1 to 0.5 and it is considered to be hot, whereas the outer cylinder is circular and it is supposed to be cold. The annular spacing between the cylinders is defined based on radii ratio (RR = 2.5). Also, the inner cylinder is inclined with an inclination angle (θ = 0 to 90). The main purpose of this study is to determine the effects of inclination angle (θ = 0° to 90°), aspect ratio of inner cylinder (E = 0.1 to 0.5), Prandtl number (Pr = 0.71 and 7.01) and Rayleigh number (Ra = 103 to 105) on fluid flow and heat transfer rate. The flow patterns and temperature distributions are potted in terms of streamlines and isotherms respectively. The obtained results showed that increase in inclination angle enhances the heat transfer rate of inner cylinder for all values of aspect ratio. Also, for the inclination angle (θ = 90°), the decrease in aspect ratio (E) improves the heat transfer rate of inner cylinder.

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Experimental Investigation on Effect of Inclination Angle of a Flat Plate Solar Air Collector

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/945/1/012003 ◽

2021 ◽

Vol 945 (1) ◽

pp. 012003

Author(s):

K.S. Ong ◽

K. Gobi ◽

C. H. Lim ◽

J.C. Tan ◽

S. Naghavi ◽

...

Keyword(s):

Experimental Investigation ◽

Natural Convection ◽

Flat Plate ◽

Inclination Angle ◽

Power Production ◽

Air Cooling ◽

Pv Panel ◽

Air Heating ◽

Solar Air Collector ◽

Hot Weather

Abstract This study investigates the effect of inclination angle of a flat plate solar air collector in Kampar, Malaysia. Flat plate solar air collectors have been investigated since the early 1950s for air heating and crop drying. Their performances under natural convection air cooling are very similar to a photovoltaic (PV) panels for power production. A PV panel becomes hot when operating under hot weather which will affect the efficiency and lifespan. The panel could be cooled down by providing an air duct underneath which allowing natural convection air circulating inside the duct. The degree of cooling would depend upon the angle of inclination of the panel. This paper presents some experimental results on the effect of inclination angle on the performance of a flat plate solar air collector under natural convection air cooling.

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