Heat transfer simulation of annular elliptical fin-and-tube heat exchanger by transition SST model
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Heat transfer simulation of annular elliptical fin-and-tube heat exchanger by transition SST model H NEMATI1, A R RAHIMZADEH2, WANG Chi-chuan3 1. Department of Mechanics, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran; 2. Mechanical Engineering, Islamic Azad University, Bushehr branch, Bushehr, Iran; 3. Department of Mechanical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan, China © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: In this study, thermo-fluid characteristics of elliptical annular finned tube heat exchanger were numerically studied in detail. Transition SST model was utilized to simulate turbulent flow. Effects of air velocities, horizontal to vertical fin diameter ratios, and fin densities were examined in detail. The simulations indicate superior performance of elliptical fin layout. It was shown that pressure drop of annular elliptical fin can be only one half of that of a circular annular fin while containing comparable heat transfer performance. The vertical elliptical annular fin may even contain a higher heat transfer performance over circular fin. Correlations are proposed to estimate the Nu number and pressure drop based on the annular circular fin. The maximum deviations between the proposed correlations and simulations regarding pressure drop and heat transfer coefficient are 5.6% and 3.2%, respectively. For further elaboration of the superiority of the elliptical layout from the second law perspective, normalized entropy generation was also studied. In all cases, the entropy generation rate in circular fin was higher than that of an elliptical fin. Key words: annular fin; elliptical fin; entropy generation; transition SST model; tube bundle Cite this article as: H NEMATI, A R RAHIMZADEH, WANG Chi-chuan. Heat transfer simulation of annular elliptical fin-and-tube heat exchanger by transition SST model [J]. Journal of Central South University, 2020, 27(8): 2324−2337. DOI: https://doi.org/10.1007/s11771-020-4452-5.
1 Introduction Extended surface is used extensively to enhance heat transfer [1−3] and annular circular fin is a typical type of extended surfaces that is commonly used to augment heat transfer in air-cooled heat exchangers [4]. This type of fin is studied comprehensively both experimentally and numerically [5−14]. JANG et al [15] were the first people who worked numerically on annular finned tube bundle. They used both numerical and experimental methods to study heat transfer and fluid flow in a four-row annular circular finned tube heat exchanger. They assumed that the flow regime
is laminar. Later, MON et al [16] extended the modelling to turbulent fluid flow regime. The effects of fin spacing, arrangements (in-line or staggered) of the annular fins having four-row configuration were reported. NEMATI et al [17] studied different methods of turbulent flow modelling over a four-row annular finned tube and complex phenomena such as flow separation, horseshoe vortices, generated wakes were well ela
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