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research-article

Numerical analysis of natural convection heat transfer from a vertical hollow cylinder suspended in air

[+] Author and Article Information
Swastik Acharya

Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, India, 721302
swastik.acharya8@gmail.com

Sumit Agrawal

Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, India, 721302
sumit89agr@gmail.com

Sukanta K. Dash

Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, India, 721302
sdash@mech.iitkgp.ernet.in

1Corresponding author.

ASME doi:10.1115/1.4038478 History: Received March 30, 2017; Revised September 13, 2017

Abstract

Natural convection heat transfer from a vertical hollow cylinder suspended in air has been analyzed numerically by varying the Rayleigh number (Ra) in laminar (10^4 = Ra = 10^8) regime. The simulations have been carried out by changing the ratio of length to pipe diameter (L/D) in the range of 1<=L/D<=20. Full conservation equations have been solved numerically for a vertical hollow cylinder suspended in air using algebraic multi-grid solver of FLUENT 13.0. The flow field around the vertical hollow cylinder have been observed to be pretty interesting and visually stimulating for small and large L/D. It has been found that the average Nusselt number(Nu) for vertical hollow cylinder suspended in air increases with the increase in Rayleigh number and the Nu for both the inner and the outer surface also increases with Ra . However, with the increase in L/D, average Nu for the outer surface increases almost linearly whereas the average Nu for the inner surface decreases quadratically and attains asymptotic value at lower L/D for low Ra. In this study the effect of parameters like L/D and Ra on Nu are analyzed, and a correlation for average Nusselt number has been developed for laminar regime. These correlations are accurate to the level of ±6% .

Copyright (c) 2017 by ASME
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