scholarly journals Laminar Natural-Convective Heat Transfer from a Uniformly Heated Vertical Cylinder.

2001 ◽  
Vol 67 (653) ◽  
pp. 300-303 ◽  
Author(s):  
Yuji ISAHAI ◽  
Kenji SUETSUGU ◽  
Naozo HATTORI
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Vertical Cylinder

Natural Convective Heat Transfer From an Isothermal Vertical Square Cylinder Mounted on a Flat Adiabatic Base

2008 ◽  
Author(s):  
Patrick H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Cross Section ◽  
Convective Heat ◽  
Vertical Cylinder ◽  
Base Plate ◽  
Cylinder Surface ◽  
Vertical Side ◽  
Study Results ◽  
Wide Range

Natural convective heat transfer from an isothermal vertical cylinder with a square cross-section which has an exposed horizontal top surface has been numerically studied. The exposed upper surface is maintained at the same temperature as the vertical walls of the cylinder. The cylinder is mounted on a flat horizontal adiabatic base plate. The interest in this situation stems from the fact that it is an approximate model of some electrical component cooling situations. The flow has been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the three-dimensional governing equations, these equations being written in terms of dimensionless variables. The numerical solution has been obtained using a commercial finite element method based code, FIDAP. The solution has the following parameters: the Rayleigh number, Ra, based on the height of the heated cylinder, h, and the overall temperature difference Tw − Tf, the dimensionless size of the square cross-section of the cylinder surface, W = w/h, w being the size of the cross-section, and the Prandtl number, Pr. Because of the applications that motivated this study, results have only been obtained for Pr = 0.7. A wide range of the other governing parameters has been considered. The conditions under which the heat transfer from the exposed upper surface can be neglected compared to that from the vertical side walls in the evaluation of the mean Nusselt number for the entire cylinder have been explored.

Natural Convective Heat Transfer From a Vertical Cylinder With an Exposed Upper Surface

2007 ◽  
Author(s):  
Patrick H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Vertical Cylinder ◽  
Curved Surface ◽  
Curvature Effects ◽  
Study Results ◽  
Wide Range ◽  
The Mean

Natural convective heat transfer from a vertical cylinder which has a uniform heat flux at its surface and which has an exposed horizontal top surface has been numerically studied. The cylinder is mounted on an adiabatic cylindrical base which has the same diameter as the heated cylinder. In some circumstances the mean Nusselt number for the curved surface of the cylinder can be adequately predicted using vertical flat plate equations, i.e., by ignoring curvature effects, and in some circumstances the overall mean Nusselt number for the system considered can be adequately predicted by ignoring the heat transfer from the exposed upper surface of the cylinder. The flow has been assumed to be axisymetric about the vertical cylinder axis and to be steady and laminar. It has also been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the governing equations, these equations being written in terms of dimensionless variables and the solution being obtained using a commercial finite element method based code, FIDAP. Because of the applications that motivated this study, results have only been obtained for Pr = 0.7. A wide range of the other governing parameters have been considered. The conditions under which the heat transfer from the exposed upper surface can be neglected compared to that from the cylindrical wall in the evaluation of the mean Nusselt number has been deduced and the conditions under which curvature effects can be ignored in evaluating the mean Nusselt number for the curved surface of the cylinder have been investigated.

Turbulent Natural Convection From a Vertical Cylinder to an Array of Cooled Tubes

1993 ◽  
Vol 115 (4) ◽  
pp. 928-937 ◽  
Author(s):  
D. M. McEligot ◽  
C. M. Stoots ◽  
W. A. Christenson ◽  
D. C. Mecham ◽  
W. G. Lussie
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Test Section ◽  
Vertical Cylinder ◽  
Turbulent Natural Convection ◽  
Cooling Tube ◽  
Natural Convection Problem ◽  
Perforated Tube

In order to determine whether available correlations are adequate to treat a complicated, turbulent natural convection problem encountered in industrial practice, experiments were conducted by resistively heating a slender, vertical cylinder centered inside a concentric perforated tube, which was, in turn, surrounded by an array of three larger-diameter cooled tubes. The ratio of the test section temperature to the cooling tube temperature was varied up to 2.6; and the Rayleigh number, based on tube diameter and properties evaluated at the cooling tube temperature, ranged from 2.9×104 to 9.2×105. Results indicate that the convective heat transfer parameters for the perforated tube are about 15 percent higher than for the smooth bare tube centered in the same position relative to the array. The Nusselt number for convective heat transfer across the annulus between the heated test section and the perforated tube corresponded approximately to parallel laminar flow (i.e., Nus≈1).

Natural Convective Heat Transfer From an Isothermal Vertical Cylinder With an Exposed Upper Surface Mounted on a Flat Adiabatic Base

2007 ◽  
Author(s):  
Patrick H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Vertical Cylinder ◽  
Curved Surface ◽  
Curvature Effects ◽  
The Mean

Natural convective heat transfer from an isothermal vertical cylinder which has an exposed horizontal top surface has been numerically studied. The exposed upper surface is maintained at the same temperature as the cylindrical vertical wall of the cylinder. The cylinder is mounted on a flat horizontal adiabatic base plate. In some circumstances the heat transfer rate from the exposed upper surface can be neglected compared to that from the curved surface of the cylinder and in some circumstances the heat transfer rate from the curved surface can be adequately predicted using vertical flat plate equations, i.e., by ignoring curvature effects. The flow has been assumed to be axisymetric about the vertical cylinder axis. The flow has also been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the governing equations, these equations being written in terms of dimensionless variables, the solution being obtained using a commercial finite element method based code, FIDAP. Because of the applications that motivated this study, results have only been obtained for Pr = 0.7. A wide range of the other governing parameters have been considered. The conditions under which the heat transfer from the exposed upper surface can be neglected compared to that from the cylindrical wall in the evaluation of the mean Nusselt number has been deduced and the conditions under which curvature effects can be ignored in evaluating the mean Nusselt number for the curved surface of the cylinder have been investigated.

Buoyancy-Induced Natural Convective Heat Transfer Along a Vertical Cylinder Using Water–Al2O3 Nanofluids

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
S. Ravi Babu ◽  
G. Sambasiva Rao
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Radial Direction ◽  
Vertical Cylinder ◽  
Axial Direction ◽  
Alumina Nanoparticles ◽  
Fluid Temperature ◽  
Steady State Condition ◽  
Temperature Variations

Buoyancy-induced natural convective heat transfer along a vertical cylinder immersed in Water–Al2O3 nanofluids for various concentrations (0, 0.05, 0.1, 0.2, 0.4, 0.6 vol %) under constant heat flux condition was investigated experimentally and presented. Thermal stratification was observed outside the boundary layer in the ambient fluid after steady-state condition is achieved as the fluid temperature goes on increasing along the axial direction. Temperature variations of the cylinder along the axial direction and temperature variations of fluid in radial direction are shown graphically. It is observed that the temperatures of the cylinder and the fluid increases along the axial direction and the fluid temperature decreases in the radial direction. Experiments were conducted for various heat inputs (30 W, 40 W, 45 W, and 50 W) and volume concentrations and observed that the addition of alumina nanoparticles up to 0.1 vol % enhances the thermal performance and then the further addition of nanoparticles leads to deterioration. The maximum enhancement in the natural convection heat transfer performance is observed as 13.8%, i.e., heat transfer coefficient is increased from 382 W/m2 K to 435 W/m2 K at 0.1 vol % particle loading.

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