scholarly journals Discussion: “Turbulent Natural Convection on Upward and Downward Facing Inclined Constant Heat Flux Surfaces” (Vliet, G. C., and Ross, D. C., 1975, ASME J. Heat Transfer, 97, pp. 549–554)

1975 ◽  
Vol 97 (4) ◽  
pp. 554-555
Author(s):  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Turbulent Natural Convection

Turbulent Natural Convection on Upward and Downward Facing Inclined Constant Heat Flux Surfaces

1975 ◽  
Vol 97 (4) ◽  
pp. 549-554 ◽  
Author(s):  
G. C. Vliet ◽  
D. C. Ross
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Constant Heat Flux ◽  
Test Surface ◽  
Metal Foil ◽  
Constant Heat ◽  
Turbulent Natural Convection ◽  
Stable Case ◽  
Unstable Case

Local heat transfer data were obtained for turbulent natural convection on vertical and inclined upward and downward facing surfaces. The test surface consisted of a 1.83 m (6 ft) wide × 7.32 m (24 ft) high plate with a constant heat flux obtained by electrical resistive heating of a metal foil on the surface. The tests were conducted in air for modified Grashof numbers up to 1015. Measurements were made of the local surface temperature for this constant heat flux condition, for the plate inclined at angles from 30 deg to the vertical (upward facing, unstable) through the vertical to 80 deg to the vertical (downward facing, stable). The results show the location of the transition to be a function of the plate angle. For the unstable case, the transition length decreases as the plate angle increases from the vertical while for the stable case the position of transition increases with the angle from the vertical. The laminar data for both orientations are correlated as: Nux=0.55(Grx*Pr)0.20 in which the gravity is the component along the surface, g cos θ. The turbulent natural convection data are correlated quite well by the relation: Nux=0.17(Grx*Pr)0.25 In the turbulent case the correlation is independent of angle for the unstable case, whereas for the stable case the data correlate best when the gravity is modified by cos2 θ, where θ is measured from the vertical. Thus, there is a significant influence of angle on the convective heat transfer for the stable turbulent region.

Natural Convection Local Heat Transfer on Constant-Heat-Flux Inclined Surfaces

1969 ◽  
Vol 91 (4) ◽  
pp. 511-516 ◽  
Author(s):  
G. C. Vliet
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Plate Theory ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Transfer Data ◽  
Inclined Surfaces

Experimental local heat transfer data are presented for natural convection on constant-heat-flux inclined surfaces using water and air. The data extend to Grz* Pr = 1016, cover angles from the vertical to 30 deg with the horizontal, and include the laminar, transition, and turbulent regimes. In the laminar regime the data correlate well with vertical plate theory when the gravitational component parallel to the surface is used. Transition is strongly affected by inclination, the transition Grz* Pr decreasing from near 1013 for vertical surfaces to approximately 108 for a surface at 30 deg to the horizontal. The turbulent local heat transfer data correlate using the actual gravity rather than the parallel component, and indicates a change in the Grz* Pr exponent from near 0 22 for a vertical surface to approximately 1/4 as the inclination decreases. The turbulent data can be correlated quite well by Nuz = 0.30(Grz* Pr)0.24.

Nu-Ra correlations for natural convection at high Ra numbers in air-filled tilted hemispherical cavities with dome oriented upwards. Disk submitted to constant heat flux

2015 ◽  
Vol 25 (3) ◽  
pp. 504-512 ◽  
Author(s):  
Abderrahmane Baïri ◽  
Juan Mario García de María ◽  
Nacim Alilat ◽  
Najib Laraqi ◽  
Jean-Gabriel Bauzin
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Solar Energy ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Content Type ◽  
Turbulent Natural Convection ◽  
Wide Range ◽  
Building Safety ◽  
Rayleigh Numbers

Purpose – The purpose of this paper is to propose correlations between Nusselt and Rayleigh numbers for the case of inclined and closed air-filled hemispherical cavities. The disk of such cavities is subjected to a constant heat flux. The study covers a wide range of Rayleigh numbers from 5×107 to 2.55×1012. Design/methodology/approach – Correlations are obtained from numerical approach validated by experimental measurements on some configurations, valid for several angles of inclination of the cavity between 0° (horizontal disk) and 90° (vertical disk) in steps of 15°. Findings – The statistical analysis of a large number of calculations leads to reliable results covering laminar, transitional and turbulent natural convection heat transfer zones. Practical implications – The proposed correlations provide solutions for applications in several fields of engineering such as solar energy, aerospace, building, safety and security. Originality/value – The new relations proposed are the first published for high Rayleigh numbers for this type of geometry. They supplement the knowledge of natural convection in hemispherical inclined cavities and constitute a useful tool for application in various engineering areas as solar energy (thermal collector, still, pyranometer, albedometer, pyrgeometer), aerospace (embarked electronics), building, safety and security (controlling and recording sensors).

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