Heat transfer characteristics and entropy generation for wing-shaped-tubes with longitudinal external fins in cross-flow

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• 作者：Sayed Ahmed E. Sayed Ahmed ; Osama M. Mesalhy…
• 刊名：Journal of Mechanical Science and Technology
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：30
• 期：6
• 页码：2849-2863
• 全文大小：5,213 KB
• 刊物类别：Engineering
• 刊物主题：Mechanical Engineering
  Structural Mechanics
  Control Engineering
  Industrial and Production Engineering
  
• 出版者：The Korean Society of Mechanical Engineers
• ISSN：1976-3824
• 卷排序：30

文摘

A numerical study is conducted to clarify heat transfer characteristics, effectiveness and entropy generation for a bundle of wingshaped-tubes attached to Longitudinal fins (LF) at downstream side. The air-side Rea ranged from 1.8 x 103 to 9.7 x 103. The fin height (h_f) and fin thickness (δ) have been changed as: (2 mm ≤ h_f ≤ 12 mm) and (1.5 mm ≤ δ ≤ 3.5 mm). The analysis of entropy generation is based on the principle of minimizing the rate of total entropy generation that includes the generation of entropy due to heat transfer and friction losses. The temperature field around the wing-shaped-tubes with (LF) is predicted using commercial CFD FLUENT 6.3.26 software package. Correlations of Nu_a, St_a, and Bejan number (Be), as well as the irreversibility distribution ratio (Φ) in terms of Re_a and design parameters for the studied bundle are presented. Results indicated that, installing fins with heights from 2 to 12 mm results in an increase in Nua from 11 to 36% comparing with that of wing-shaped tubes without fins (NOF). The highest and lowest values of effectiveness (ε) at every value of the considered Re_a range are occurred at h_f = 6 mm and (NOF), respectively. The wing-shaped-tubes heat exchanger with h_f = 6 mm has the highest values of (ε), efficiency index (η) and area goodness factor (G_a) and also the lowest values of Φ and hence the best performance comparing with other arrangements. The minimum values of Φ are occurred at h_f = 6 mm. (Be) decreases with increasing Re_a for all studied h_f. The heat transfer irreversibility predominates for (1800 ≤ Re_a ≤ 4200) while the opposite is true for (6950 < Re_a ≤ 9700). δ has negligible effect on Nu_a and heat transfer irreversibility. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.KeywordsLongitudinal finsEntropy generationHeat transfer characteristicsFluentCross-flowWing-shaped-tubes