Prediction of the Temperature in a Long Horizontal Fin Rod Cooled by Natural Convection and Radiation

2004 ◽  
Author(s):  
Donald W. Mueller ◽  
Hosni I. Abu-Mulaweh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Elevated Temperature ◽  
Heat Loss ◽  
Cross Section ◽  
Radiative Heat ◽  
Horizontal Cylinder ◽  
Physical Situation ◽  
Fundamental Study ◽  
Finite Difference Formulation

The objective of this fundamental study is to numerically predict the temperature along a fin cooled by natural convection and radiation and to compare with measurements. The physical situation considered is a horizontal fin with a cylindrical cross-section. One end of the fin is maintained at a constant elevated temperature, and the fin is sufficiently long so that heat loss from the tip is negligible. Heat is transferred by conduction along the fin and dissipated from the surface via natural convection and radiation. The effect of natural convection is described with a published correlation for a horizontal cylinder, and a simple model is used for the radiative heat transfer. A finite difference formulation that allows for variable fluid property effects is used to determine the temperature distribution along the fin. A comparison is made to experimental results, and the agreement between the model and experiment is very good. Results show that the heat loss due to radiation is typically 15%–20% of the total.

Numerical Investigation of Natural Convection Heat Transfer from Square Cylinder in a Vented Enclosure

2011 ◽  
Vol 110-116 ◽  
pp. 4451-4464 ◽  
Author(s):  
Ghalib Y. Kahwaji ◽  
Abbas S. Hussien ◽  
Omar M. Ali
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Cross Section ◽  
Convection Heat Transfer ◽  
Grid Generation ◽  
Flow Patterns ◽  
Horizontal Cylinder ◽  
Natural Convection Heat Transfer ◽  
Computational Domain ◽  
Convection Heat

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 was investigated numerically. The work investigate the effect of the Ra, enclosure width and opening size of the enclosure on the streamlines, isotherms and heat transfer results. The numerical work included the solution of the governing equations in the vorticity-stream function formulation which were transformed into body fitted coordinate system. The transformations are based initially on algebraic grid generation and elliptic grid generation to map the physical domain between the heated horizontal cylinder and the vented enclosure into a computational domain. A hybrid scheme finite volume based finite difference method was used. The study included the following ranges of the studied variables:- 0 < Ra ≤ 6.5× 105 1.5 ≤ W/H ≤ 4 0.375 < O/H ≤ 4 The numerical results were compared with experimental results, which showed good agreement. The effect of cylinder cross section, Ra, enclosure width, and opening size on the Nu, mass flowrate, flow patterns and isotherms were investigated. The results show that the cylinder cross section has a large influence on the results especially the Nu. The Nu is proportional with Ra and inversely proportional with enclosure width and opening size. The flow patterns and isotherms display the flow and temperature behaviors with changing studied variables. The results show that the starting of natural convection heat transfer depended on the cylinder cross-section, enclosure width and opening size in addition with Ra. In addition, the results display that the hydrodynamic and thermal boundary layer thickness decreases with increasing Ra. Nomenclature

Onset of Natural Convection from a Suddenly Heated Horizontal Cylinder

1980 ◽  
Vol 102 (4) ◽  
pp. 636-639 ◽  
Author(s):  
J. R. Parsons ◽  
J. C. Mulligan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Stability ◽  
Heat Capacity ◽  
Natural Convection ◽  
Stability Analysis ◽  
Horizontal Cylinder ◽  
Finite Cylinder ◽  
Global Motion ◽  
Experimental Apparatus

A study of the onset of transient natural convection from a suddenly heated, horizontal cylinder of finite diameter is presented. The termination of the initial conductive and “locally” conuectiue heat transfer regime which precedes the onset of global natural convection is treated as a thermal stability phenomenon. An analysis is presented wherein the effects of finite cylinder diameter, cylinder heat capacity, and cylinder thermal conductivity are included in calculations of the convective delay time. A simple experimental apparatus is described and data presented. The thermal stability analysis is confirmed experimentally and data is presented which indicates localized natural convection prior to global motion.

THE COEFFICIENT OF HEAT TRANSFER FOR VERTICAL SURFACES IN STILL AIR

1937 ◽  
Vol 15a (7) ◽  
pp. 109-117
Author(s):  
R. Ruedy
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Loss ◽  
Temperature Difference ◽  
Plane Surface ◽  
Vertical Plane ◽  
Black Body ◽  
Average Temperature ◽  
Fourth Root

For a vertical plane surface in still air the coefficient of heat transfer, valid within the range of temperatures occurring in buildings, depends on the temperature and the height of the surface. If black body conditions are assumed for the heat lost by radiation, the coefficient is equal to 1.39, 1.50, 1.62, and 1.73 B.t.u. per sq. ft. per ° F. at 32°, 50°, 68°, and 86° F. respectively, the height of the heated surfaces being 100 cm. Convection is responsible for about one-third, and radiation, mainly in the region of 10 microns, for about two-thirds of the heat loss. Convection currents depend on the temperature difference, while radiation depends on the average temperature. When attempts are made to stop convection currents by placing obstacles across the surface, the loss of heat due to natural convection varies inversely as the fourth root of the height, providing that the nature of the flow of air remains unchanged.

Heat transfer of combined forced and natural convection from horizontal cylinder to air

2007 ◽  
Vol 36 (8) ◽  
pp. 474-488 ◽  
Author(s):  
Kenzo Kitamura ◽  
Kazuhiro Mototani ◽  
Fumiyoshi Kimura
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Horizontal Cylinder

scholarly journals Steady state analysis of regular hollow pyramidal radiating fin with triangular cross-section

2015 ◽  
Vol 19 (1) ◽  
pp. 59-68
Author(s):  
Vijaikrishnan Venkataramanan ◽  
Ramakrishnan Madhavaneswaran ◽  
Siva Shanmugam
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Cross Section ◽  
Working Conditions ◽  
Unit Mass ◽  
Design Parameters ◽  
Steady State Analysis ◽  
Fin Efficiency ◽  
Triangular Cross Section ◽  
Optimum Parameters

A new configuration for space radiator is proposed introducing a fin of regular hollow pyramidal shape with triangular cross section, giving a higher improvement in heat loss per unit mass than that of other corresponding configurations previously proposed under same working conditions. The significance of the present configuration and its advantage over other regular hollow configurations are discussed and effect of various design parameters on heat transfer is analyzed in presence of radiation interaction with an isothermal base attached to it. Optimum parameters are identified for which improvement in heat loss per unit mass is the maximum. It is found that the fin efficiency decreases with increase in the emissivity & height of the fin and increases with increase in thickness & top radius of the fin. Correlations are presented for optimum design parameters, optimum improvement in heat loss per unit mass and fin efficiency.

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