Abstract
Natural convection heat transfer from a vertical barrel-shaped solid/hollow cylinder to air in the infinite surroundings in a laminar regime ( 10 4 ≤ Ra ≤ 10 8 ) numerically analyzed. The effect of Ra , length-to-diameter ratio ( 2 ≤ L / D ≤ 10 ) , and maximum diameter-to-diameter ratio ( 1.2 ≤ D max / D ≤ 1.9 ) has been investigated on the heat dissipation to the surroundings. The heat dissipation and the Nu ¯ increase with Ra for solid/hollow cylinders. We found that Nu ¯ out is always larger than Nu ¯ in . At a high L / D ratio, heat dissipation from the inner surface of a hollow cylinder remains constant for the entire range of D max / D ratios. But at a low D max / D and high Ra (i.e. Ra ≥ 106), Nu ¯ out for a hollow cylinder significantly decreases with D max / D ; whereas, it shows a marginal decrement at a high L / D ratio. The thermo-fluid dynamics have been delineated through the thermal plume, velocity vectors, and vortex generation at the inner and outer surfaces. Empirical correlations have also been developed.
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