EXPERIMENTAL ANALYSIS OF NATURAL CONVECTION OVER A VERTICAL CYLINDER (original) (raw)
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EXPERIMENTAL ANALYSIS OF NATURAL CONVECTION OVER A VERTICAL CYLINDER AT UNIFORM TEMFERATURE
In the present work, an experimental study of natural convection heat transfer in vertical circular cylinders immersed in air at uniform wall temperature has been presented. The outcome of the study is summarized with practical correlation equations linking to the Nusselt number to the Rayleigh number and Prandtl number. The proposed regression model was good agreement with the regression models given by previous authors.
Numerical Investigation of Natural Convection Heat Transfer from a Cylinder in a Vented Enclosure
AL-Rafdain Engineering Journal (AREJ)
In this work, Natural convection heat transfer from a horizontal cylinder placed in a vented enclosure was investigated numerically to infer the effect of Rayleigh number (Ra) having the values 1*10 4 , 5*10 4 and 1*10 5 , the effect of the ratio of the enclosure width to the cylinder diameter (W/D) having the values 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3 and 3.5, the effect of the ratio of the vent size to the enclosure width (O/W) for a range starting from 0 for a closed enclosure to 1 for an enclosure having two vertical walls only, and the effect of time variation, on the Nusselt number (Nu), the mass flow-rate, the flow and temperature patterns as well as the boundary layers, where the results showed that, Nu. number always increased with Ra. Number. Furthermore, Nu. number increased with the increase of the ratio W/D for ratios of O/W greater than 0.25, and Nu. number decreases with the increase of W/D for the range below this value.
Numerical simulations of natural convection heat transfer along a vertical cylinder
International Journal of Numerical Methods for Heat & Fluid Flow, 2011
PurposeThe purpose of this paper is to present a numerical solution for the problem of steady laminar flow and heat transfer characteristics of viscous incompressible fluid.Design/methodology/approachFor this purpose a two dimensional code has been developed to simulate the natural convection heat transfer along a vertical cylinder, for four different geometries: from vertical cylinder in infinite medium; from a vertical flat plate in an infinite medium; from an open assembly of a finite vertical cylinder; and from an open rectangular pitch assembly of cylinders.FindingsThe effects of various parameters of interest have been discussed through simulations. The Nusselt numbers of constant wall temperature and constant heat flux cylinders calculated numerically and compared with Lee et al. and Heckel et al., respectively, and are found within reasonable agreement. For large radius, a vertical cylinder has been treated as a vertical flat plate, so that the curvature effects become negli...
Applied Thermal Engineering, 2011
Steady state heat transfer by natural convection was investigated experimentally from an enclosed assembly of thin vertical cylinders at high Rayleigh numbers. The published literature lacks any information regarding such a study in the turbulent boundary layer regime. All the available literature is for the laminar region for an enclosed assembly. The enclosed assembly consisted of a 3 Â 3 array of vertical cylinders immersed in a large volume tank of water. All the cylinders were electrically heated. Uniform heat fluxes at various power levels were applied to each cylinder and the surface temperature at different positions along the cylinders were recorded. The experimental results show that the surface temperature distribution increases axially up to a certain length, then decreases due to mixing which increases the heat transfer. The heat transfer coefficient, Nusselt number and modified Rayleigh number have also been presented for the experimental data. Empirical correlations between overall Nusselt number and average modified Rayleigh number have been developed for an assembly of cylinders. This empirical correlation for an assembly is valid for 1.28 Â 10 12 Ra * L 1.18 Â 10 13 . The maximum natural convection at central cylinder and Chimney effects in an assembly are observed during these experiments.
Natural Convection Heat Transfer In an Inclined Circular Cylinder
The Journal of Engineering, 2011
Experiments were carried out to investigate natural convection heat transfer in an inclined uniformly heated circular cylinder . The effects of surface heat flux and angle of inclination on the temperature and local Nusselt number variations along the cylinder surface are discussed . The investigation covers heat flux range from 92 W/m² to 487 W/m², and angles of inclination 0° ( horizontal) , 30° , 60° and 90° (vertical) . Results show an increase in the natural convection as heat flux increases and as angle of inclination moves from vertical to horizontal position. An empirical equation of average Nusselt number as a function of Rayliegh number was deduced for each angle of inclination .
NATURAL CONVECTION HEAT TRANSFER INSIDE INCLINED OPEN CYLINDER
Natural convection is investigated experimentally in an inclined open cylindrical passege heated under constant heat flux condition to study the effect of angle of inclination and heat flux on heat transfer. Heat transfer results are given for inclination angles of 0o (horizontal), 30o, 60o and 90o (vertical).Using cylinder diameter of 4.8 cm, cylinder length 50 cm and heat flux from 70 W/m2 to 600 W/m2. Empirical correlations are given for the average Nusselt number as a function of the Rayleigh number. The results show that the local and average Nusselt number increase as the heat flux increase and when angle of inclination changed from 0o (horizontal) to 90o (vertical). An empirical correlations of average Nusselt number as a function of Rayleigh number were obtained
ABSTRACT In the present work, the natural convection heat transfer from horizontal cylinder with square cross section situated in a square enclosure, vented symmetrically from the top and the bottom is investigated experimentally. The experimental work includes temperature measurements of the cylinder surface and the environment during transient state to determine Nu for the unbound and the bound cylinder. The studied variable ranges were: 107 ≤ Ra ≤ 6.6× 107, 2 ≤ W/D ≤ 4, 0.25 ≤ O/D ≤ 4. The results indicated an increase in Nu with increasing Ra. Furthermore, Nu increased proportionally with the vent opening size at low enclosure widths. It showed inverse proportionality with opening size for high enclosure widths. The maximum percentage of the enhancement is more than 20% for bounded square cylinder as compared with unbounded square cylinder. Keywords: Heat Transfer, Square Cylinder, Enclosure, Experimental
International Communications in Heat and Mass Transfer, 2007
Combined convection heat transfer in a vertical circular cylinder has been experimentally studied for assisting, thermally developing and thermally fully developed laminar air flows under constant wall heat flux boundary conditions for Reynolds number range from 400 to 1600, and the heat flux is varied from 60 Wm − 2 to 400 Wm − 2 . This paper has examined the effect of the cylinder inclination angle on the mixed convection heat transfer process. The experimental setup consists of aluminum cylinder as test section with 30 mm inside diameter and 900 mm heated length (L / D = 30). The hydrodynamically developed condition has been achieved by using aluminum entrance section pipes (calming sections) having the same inside diameter as test section pipe but with variable lengths. The entrance sections included two long calming sections, one with length of 1800 mm (L / D = 60), another one with length of 2400 mm (L / D = 80) and two short calming sections with lengths of 600 mm (L / D = 20), 1200 mm (L / D = 40). The results present the surface temperature distribution along the cylinder length, the local and average Nusselt number distribution with the dimensionless axial distance Z + . The results have clearly shown that the surface temperature values decrease as the cylinder inclination angle moves from θ = 90°vertical cylinder to θ = 0°horizontal cylinder. The results have demonstrated that an increase in the Nusselt number values as the heat flux increases and as the angle of cylinder inclination moves from θ = 90°vertical cylinder to θ = 0°horizontal cylinder. The mixed convection regime has been bounded by the convenient selection of Re number range and the heat flux range, so that the obtained Richardson numbers (Ri) varied approximately from 0.1 to 10. The average heat transfer results have been correlated with an empirical correlation by dimensionless groups as Log P Nu against Log P Ra= P Re, and compared with available literature and with laminar forced convection and showed satisfactory agreement.
Free Convection Heat Transfer from Horizontal Cylinders
Energies, 2021
The results of experimental investigation of free convection heat transfer in a rectangular container are presented. The ability of the commonly accepted correlation equations to reproduce present experimental data was tested as well. It was assumed that the examined geometry fulfils the requirement of no-interaction between heated cylinder and bounded surfaces. In order to check this assumption recently published correlation equations that jointly describe the dependence of the average Nusselt number on Rayleigh number and confinement ratios were examined. As a heat source served electrically heated horizontal tube immersed in an ambient fluid. Experiments were performed with pure ethylene glycol (EG), distilled water (W), and a mixture of EG and water at 50%/50% by volume. A set of empirical correlation equations for the prediction of Nu numbers for Rayleigh number range 3.6 × 104 < Ra < 9.2 × 105 or 3.6 × 105 < Raq < 14.8 × 106 and Pr number range 4.5 ≤ Pr ≤ 160 has b...