scholarly journals Experiments on Natural-Convection Heat Transfer from the Outer Surface of a Vertical Cylinder to Liquids: 1st Report Non-dimensional Expressions of Heat Transfer Coefficients by the Physical Properties at a Reference Temperature

1969 ◽  
Vol 35 (280) ◽  
pp. 2381-2389 ◽  
Author(s):  
Tetsu FUJI ◽  
Masanori TAKEUCHI ◽  
Haruo UEHARA ◽  
Hideaki IMURA
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Physical Properties ◽  
Outer Surface ◽  
Convection Heat Transfer ◽  
Vertical Cylinder ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Experimental Investigation of Natural Convection Heat Transfer in Volumetrically Heated Spherical Segments

1996 ◽  
Vol 118 (1) ◽  
pp. 31-37 ◽  
Author(s):  
F. J. Asfia ◽  
B. Frantz ◽  
V. K. Dhir
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Reactor Vessel ◽  
Core Material ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
External Cooling

External cooling of a light water reactor vessel by flooding of the concrete cavity with subcooled water is one of several management strategies currently being considered for accidents in which significant relocation of core material is predicted to occur. At present, uncertainty exists with respect to natural convection heat transfer coefficients between the pool of molten core material and the reactor vessel wall. In the present work, experiments were conducted to examine natural convection heat transfer in internally heated partially filled spherical pools with external cooling. In the experiments, Freon-113 was contained in a Pyrex bell jar, which was cooled externally with subcooled water. The pool was heated using a 750 W magnetron taken from a conventional microwave. The pool had a nearly adiabatic free surface. The vessel wall temperature was not uniform and varied from the stagnation point to the free surface. A series of chromel–alumel thermocouples was used to measure temperatures in both steady-state and transient conditions. Each thermocouple was placed in a specific vertical and radial location in order to determine the temperature distribution throughout the pool and along the inner and outer walls of the vessel. In the experiments, pool depth and radius were varied parametrically. Both local and averages heat transfer coefficients based on pool maximum temperature were obtained. Rayleigh numbers based on pool height were varied from 2 × 1010 to 1.1 × 1014. Correlations for the local heat transfer coefficient dependence on pool angle and for the dependence of average Nusselt number on Rayleigh number and pool depth have been developed.

Natural Convection Heat Transfer From Horizontal Rectangular Fin Arrays

1967 ◽  
Vol 89 (1) ◽  
pp. 32-38 ◽  
Author(s):  
F. Harahap ◽  
H. N. McManus
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Field ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients

Average heat-transfer coefficients are presented for fin arrays positioned with the base oriented horizontally. The flow field associated with the natural convection from the fin arrays was investigated and used as a model to find parameters to generalize the data. The proposed correlation overcomes the inadequacy of parameters available previously for horizontal rectangular fins.

Natural Convection Heat Transfer From a Staggered Vertical Plate Array

1993 ◽  
Vol 115 (4) ◽  
pp. 938-945 ◽  
Author(s):  
G. Tanda
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Vertical Plate ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

An experimental study was performed to evaluate the natural convection heat transfer characteristics of an array of four staggered vertical plates. The thermal input at each plate was the same or differed from plate to plate depending on various heating modes. The effects of the interplate spacing and the plate-to-ambient temperature difference were investigated. The experiments were performed in air. Convective interactions among the plates were identified by examining the per-plate heat transfer coefficients and the local heat transfer coefficients along the vertical sides of plates. Local heat transfer results were obtained by means of the schlieren quantitative technique. Comparison of local heat transfer coefficients along the plate assembly with those of a continuous vertical plate (having the same height) showed enhancements up to a factor of two. Comparison of average heat transfer results with those for a parallel plate channel having the same exchanger size showed only little reductions in heat transfer rate, despite a 28 percent reduction in heat transfer area, with enhancements, in terms of specific heat flux, up to 30 percent.

Natural Convection in the Annulus Between Horizontal Circular Cylinders With Three Axial Spacers

1982 ◽  
Vol 104 (1) ◽  
pp. 118-124 ◽  
Author(s):  
S. S. Kwon ◽  
T. H. Kuehn ◽  
T. S. Lee
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Conjugate Natural Convection ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Conjugate natural convection heat transfer in an annulus between horizontal isothermal circular cylinders with three equally spaced axial spacers has been studied theoretically and experimentally. A thin-fin approximation was used to model the thermal boundary condition of the spacers in the two-dimensional finite difference numerical computations. Rayleigh number, Prandtl number, diameter ratio, and location and thermal conductivity of the spacers were varied parametrically to determine the variation in flow patterns, temperature distribution and heat transfer. Spacers of low conductivity can decrease the natural convection heat transfer by as much as 20 percent below that for a simple unobstructed annulus. However, radial conduction through spacers of high conductivity overwhelms the natural convection heat transfer between the cylinders. Two diameter ratios were tested experimentally in a Mach-Zehnder interferometer using air at atmospheric pressure with stainless steel spacers between copper cylinders. The numerical and experimental temperature distributions and local convective heat-transfer coefficients show good agreement.

Natural Convection Heat Transfer From Horizontal Rectangular Ducts

2006 ◽  
Vol 129 (9) ◽  
pp. 1195-1202 ◽  
Author(s):  
Mohamed E. Ali
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Rayleigh Numbers

Experimental investigations have been reported on steady state natural convection from the outer surface of horizontal ducts in air. Five ducts have been used with aspect ratios (Γ=duct height/duct width) of 2, 1, and 0.5. The ducts are heated using internal constant heat flux heating elements. The temperatures along the surface and peripheral directions of the duct wall are measured. Longitudinal (circumference averaged) heat transfer coefficients along the side of each duct are obtained for laminar and transition regimes of natural convection heat transfer. Total overall averaged heat transfer coefficients are also obtained. Longitudinal (circumference averaged) Nusselt numbers are evaluated and correlated using the modified Rayleigh numbers for transition regime using the axial distance as a characteristic length. Furthermore, total overall averaged Nusselt numbers are correlated with the modified Rayleigh numbers, the aspect ratio, and area ratio for the laminar and transition regimes. The longitudinal or total averaged heat transfer coefficients are observed to decrease in the laminar region and to increase in the transition region. Laminar regimes are obtained only at very small heat fluxes, otherwise, transitions are observed.

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