NATURAL CONVECTION FROM HORIZONTAL CYLINDERS OF DIFFERENT SHAPES IN A RECTANGULAR ENCLOSURE

Natural convection in a porous medium bounded by two horizontal cylinders is studied by solving the two-dimensional Boussinesq equations numerically. An accurate second-order finite difference scheme using an alternating direction method and successive underrelaxation is applied to a very fine grid. For a radius ratio above 1.7 and for Rayleigh numbers above a critical value, a closed hysteresis loop (indicating two possible solutions depending on initial conditions) is observed. For a radius ratio below 1.7 and as the Rayleigh number is increased, the number of cells in the annulus increases without bifurcation, and no hysteresis behavior is observed. Multicellular regimes and hysteresis loops have also been reported for fluid layers of same geometry but several differences between these two cases exist.

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Natural-Convection Film-Boiling Heat Transfer. (3rd Report. Film-Boiling from Horizontal Cylinders in Middle- and Small-Diameter Regions).

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.57.2124 ◽

1991 ◽

Vol 57 (538) ◽

pp. 2124-2131

Author(s):

Shigefumi NISHIO ◽

Hiroyasu OHTAKE

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Boiling Heat Transfer ◽

Small Diameter ◽

Film Boiling ◽

Horizontal Cylinders

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Natural Convection From Isothermal Horizontal Cylinders

Volume 9: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B and C ◽

10.1115/imece2009-11213 ◽

2009 ◽

Cited By ~ 2

Author(s):

Ian M. O. Gorman ◽

Darina B. Murray ◽

Gerard Byrne ◽

Tim Persoons

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Local Heat Transfer ◽

Local Heat ◽

Separation Distance ◽

Thermal Plume ◽

Number Range ◽

Vertically Aligned ◽

Isothermal Cylinders ◽

Horizontal Cylinders

The research described here is concerned with natural convection from isothermal cylinders, with a particular focus on the interaction between a pair of vertically aligned cylinders. Prime attention was focused on how the local heat transfer characteristics of the upper cylinder are affected due to buoyancy induced fluid flow from the lower cylinder. Tests were performed using internally heated copper cylinders with an outside diameter 30mm and a vertical separation distance between the cylinders ranging from two to three cylinder diameters. Plume interaction between the heated cylinders was investigated within a Rayleigh number range of 2×106 to 6×106. Spectral analysis of the associated heat transfer interaction is presented showing that interaction between the cylinders causes oscillation of the thermal plume. The effect of this oscillation is considered as a possible enhancement mechanism of the heat transfer performance of the upper cylinder.

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