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Research Papers: Natural and Mixed Convection

Natural Convection Heat Transfer From a Short or Long, Solid or Hollow Horizontal Cylinder Suspended in Air or Placed on Ground

[+] Author and Article Information
Swastik Acharya

Department of Mechanical Engineering,
Indian Institute of Technology Kharagpur,
BRH, A—513,
Kharagpur 721 302, India
e-mail: swastik.acharya8@gmail.com

Sukanta K Dash

Professor
Department of Mechanical Engineering,
Indian Institute of Technology Kharagpur,
Kharagpur 721 302, India
e-mail: sdash@mech.iitkgp.ernet.in

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received December 7, 2016; final manuscript received January 28, 2017; published online March 21, 2017. Assoc. Editor: Zhixiong Guo.

J. Heat Transfer 139(7), 072501 (Mar 21, 2017) (13 pages) Paper No: HT-16-1792; doi: 10.1115/1.4035919 History: Received December 07, 2016; Revised January 28, 2017

Numerical simulations have been conducted to study natural convection heat transfer from solid or hollow cylinders in the laminar range of Ra spanning from 104 to 108 for L/D in the range of 0.05(L/D)20. Interesting flow structures around the thin hollow cylinder have been observed for small and large L/D. It has been found that the average Nu for solid or hollow horizontal cylinders in air is marginally higher than when they are on ground for the entire range of L/D and Ra limited up to 107. Up to a Ra of 107 Nu for a solid cylinder in air is higher than that of Nu for a hollow cylinder in air but when Ra exceeds 107 Nu for a hollow cylinder is marginally higher than that of the solid cylinder until an L/D of 0.2. When, L/D rises beyond 0.2 the situation reveres causing Nu for a solid cylinder to be again higher than that of the hollow cylinder when suspended in air. A solid cylinder on ground has higher Nu compared to that of a hollow cylinder on ground up to a Ra of 106. However, for higher Ra of 108 a hollow cylinder on ground has higher Nu compared to that of a solid cylinder on ground until an L/D of 5 and after that the situation reverses again.

Copyright © 2017 by ASME
Topics: Cylinders
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References

Figures

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Fig. 1

Flow vector around a (a) hollow and (b) solid isothermal cylinder on ground, L/D = 1, Ra = 10

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Fig. 2

(a) A solid or thin hollow cylinder in air with the computational domain around it, (b) solid or the thin hollow cylinder lying on ground with its computational domain (aschematic representation)

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Fig. 3

Influence of domain height on average Nu for a solid cylinder in air

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Fig. 4

(a) Cell arrangement for hollow cylinder in air, (b) cross-sectional view, and (c) blown up view near the cylinder wall

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Fig. 5

Average Nu for a hollow cylinder in air as a function of number of cells

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Fig. 6

Average Nu for a solid cylinder in air, a comparison with experimental correlation

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Fig. 7

(a) Average Nu for a solid cylinder in air or lying on ground as a function of L/D and (b) average Nu for a hollow cylinder in air or lying on ground as a function of L/D

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Fig. 8

Temperature plume near a hollow cylinder on (a) ground and in (b) air, Ra = 108, L/D = 5

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Fig. 9

Average Nu for a solid cylinder in air or ground when end faces are isothermal

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Fig. 10

Comparison of Nu between a solid and hollow cylinder in air

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Fig. 11

Comparison of Nu between a solid and hollow cylinder on ground

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Fig. 12

Comparison of heat loss from the outer and inner surface of a hollow cylinder when placed in air

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Fig. 13

Comparison of heat loss from the outer and inner surface of a hollow cylinder when placed on ground

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Fig. 14

Velocity vector around a hollow cylinder placed on ground for Ra = 106, L/D (a) 0.5, (c) 1, and (e) 2

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Fig. 15

Temperature plume around a hollow cylinder at Ra = 106 and L/D (a) 1, (b) 2, and (c) 5 when the cylinder is in air

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Fig. 16

Temperature plume around a hollow cylinder at Ra = 106 and L/D (a) 1, (b) 2, and (c) 5 when the cylinder is on ground

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Fig. 17

Thermal plume around a short solid cylinder in air (a)–(b) and ground (c)(d), Ra = 106

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Fig. 18

velocity vector around a short solid cylinder in air (a)–(b) and ground (c)–(d), Ra = 106

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Fig. 19

Thermal buoyant plume around a solid and hollow cylinder in air or ground

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Fig. 20

A comparison of predicted Nu with that of the computed value for a solid cylinder in air

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