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Applied Thermal Engineering 51 (2013) 539e550

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Applied Thermal Engineering
journal homepage: www.elsevier.com/locate/apthermeng

New method for designing an effective finned heat exchanger
Diala Karmo a, *, Salman Ajib b, Ayman Al Khateeb c
Institute of Thermodynamics and Fluid Mechanics, Ilmenau University of Technology, Helmholtzring1, 98693 Ilmenau, Germany Department for Environmental Engineering and Applied Informatics, Section Renewable Energies and Decentralized Energy Supplying, Hochschule Ostwestfalen-Lippe, Wilhelmshöhe 44, 37671 Höxter, Germany c Department for Industrial Engineering, Faculty of Mechanical Engineering, Ilmenau University of Technology, Gustav-Kirchhoff-Platz 2, 98693 Ilmenau, Germany
b a

h i g h li g h t s
< We develop a method for designing an effective finned heat exchanger. < This new design characterize by smaller dimensions of the heat exchanger. < The tubes bend in a zigzag shape. Consequently, the fin block forms a zigzag shape. < The new design leads to significant increase in the heat transfer.

a r t i c l e i n f o
Article history: Received 10 May 2012 Accepted 28 September2012 Available online 8 October 2012 Keywords: Zigzag shape Corrugated fin-tube exchangers Heat transfer enhancement Pressure drop Numerical simulation CFD

a b s t r a c t
This paper presents a computational analysis of the heat transfer and pressure drop in a finned tube heat exchanger. The main objectives are to develop a method for designing an effective finned heat exchanger through changingthe arrangement of the fins and tubes so that the tubes can be bent in a zigzag shape. Thus, they present an angle of less than 90 to the vertical fins. Consequently, the fin block forms a zigzag shape. The construction and the dimensions of the developed alternative heat exchanger are comprehensively presented. This new design is characterized by smaller dimensions of the heat exchanger and allows anincrease of the heat transfer on the surface of the fins. Furthermore, a slight increase in the fan and pump power can result, which is very small compared with the recovered heat transfer. However, an effective model is analyzed by means of the computational fluid dynamics (CFD), FLUENT code, which is used to solve the equation for the heat transfer and pressure drop. The major results of the workshow an increase in the heat transfer value of 59.13% in comparison to the existing old model. This increase is also accompanied by an increase in the ratio between the total power consumption and the amount of heat transfer obtained of 3.84% compared to 0.8% in the old model. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction and problem description Finned tube heat exchangers arewidely used in thermal engineering applications. Due to their fins, a large total heat transfer area can be provided. In this case, many studies have been carried out in order to enhance the convective heat transfer of finned tube heat exchangers. Therefore, many investigations into heat transfer performance characteristics of the finned tube exchangers have been experimentally and numerically executed.Most of these focus on the change of the geometrical parameters of tubes and fins and, accordingly, their shape. For example, the diameter of the tubes, their arrangement and forms have been investigated under various

* Corresponding author. Tel.: þ49 3677 69 2414; fax: þ49 3677 69 2411. E-mail address: diala.karmo@tu-ilmenau.de (D. Karmo). 1359-4311/$ e see front matter Ó 2012 Elsevier Ltd. Allrights reserved. http://dx.doi.org/10.1016/j.applthermaleng.2012.09.042

conditions by Kaminski and Groß [1], István [2] and Lu et al. [3]. The effect of the number of tube rows on the efficiency of finned tube heat exchangers has numerically been investigated by Kaminski [4]. He showed that increasing the number of tube rows causes a decrease in the heat transfer coefficient and an increase in...