Caracteristicas De La Transferencia De Calor Por Conveccion

International Communications in Heat and Mass Transfer 32 (2005) 557 – 564
www.elsevier.com/locate/ichmt

Characteristics of forced convection heat transfer in vertical internally finned tubeB
A. Al-Sarkhi*, E. Abu-Nada
Department of Mechanical Engineering, Hashemite University, Zarqa, 13115, Jordan Available online 19 December 2004

Abstract This work presents a numerical investigation ofa vertical internally finned tube subjected to forced convection heat transfer. The governing equations were solved numerically using the control volume technique. Nusselt number, Nu, and friction factor multiplied by Reynolds number, fRe, are influenced greatly by the height and number of the radial fins. The velocity and temperature distributions inside the tube depend on the number and heightof the radial fins. This paper suggests that for best heat transfer to be achieved there is an optimum combination of fin numbers and height. D 2004 Elsevier Ltd. All rights reserved.
Keywords: Forced convection heat transfer; Vertical internally finned tube; Control volume technique

1. Introduction Internally finned tubes have received considerable attention because of the fact that they havebeen used widely in industrial applications. Internally finned tube has found extensive use in heat exchangers. When improvement in the process of heating or cooling is required, then better design of fin compactness and spatial geometry is very essential. Several studies have been conducted to investigate the effect of fin characteristics on heat transfer. Most of the relevant previous workshave focused on limited cases of the number and length of the internal fin shown in Fig. 1. Masliyah and Nandakumar
B

Communicated by J.P. Hartnett and W.J. Minkowycz. * Corresponding author. Tel.: +962 591 6600; fax: +962 591 6613. E-mail address: alsarkh@hu.edu.jo (A. Al-Sarkhi).

0735-1933/$ - see front matter D 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.icheatmasstransfer.2004.03.015

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A. Al-Sarkhi, E. Abu-Nada / Int. Commun. Heat and Mass Transf. 32 (2005) 557–564

Fig. 1. Schematic of radial fins and the calculation domain.

[1] have studied the heat transfer in internally finned tube. The internal fins were of triangular shape and the number of fins was changed up to 24 fins and the length up to 0.8 of the tube radius. Finite element method was used toanalyze a laminar fully developed flow in an internally finned circular tube with uniform axial heat flux around the wall. They conclude that the Nusselt number based on the inside diameter was higher than that for a smooth tube without fins and also they found that for maximum heat transfer there exists an optimum fin number for a given fin configuration. The influence of the buoyancy force incombined free and forced convection in vertical tubes with internal fins was studied by Patankar and Prakash [2]. A laminar fully developed flow was solved for the velocity and temperature using finite difference technique. Straight radial fin configurations were analyzed for a range of Rayleigh number and for various values of fin height up to 0.8 of the tube radius and number of fins up to 25 fins.In their result they found that the buoyancy force increases the friction and heat transfer. The effect of buoyancy is more significant when the number of fins is small and the fins are short. For smooth finless circular tube, the fully developed combined forced and free convection has been solved analytically by Morton [3] and also by Tao [4] and investigated numerically by Kemeny and Somers [5].Numerous studies have been focused on studying different shapes and arrangement of longitudinal shrouded fin array [6–13]. The problem of laminar fully developed flow in circular tube with internal radial fins has been studied numerically by Masiliyah and Nandakumar [1] and analytically by Hu and Chang [14]. However, detailed studies for a wide range of fin number practically encountered in the...