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Appl. Sci. 2018, 8(2), 181;

Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators

Department of Energy and Environmental Engineering, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga-shi, Fukuoka 816-8580, Japan
Department of Mechanical Engineering, Faculty of Engineering, Sebelas Maret University, Jl. Ir. Sutami 36 A, Surakarta 57126, Indonesia
Thermal Science and Engineering Division, International Institute of Carbon-Neutral Energy Research (I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
Authors to whom correspondence should be addressed.
Received: 29 December 2017 / Revised: 22 January 2018 / Accepted: 24 January 2018 / Published: 26 January 2018
(This article belongs to the Special Issue Sciences in Heat Pump and Refrigeration)
Full-Text   |   PDF [2885 KB, uploaded 26 January 2018]   |  


The impact of double-sided delta-winglet tape (DWTs) inserts on convective heat transfer and friction behaviors in a tube was experimentally investigated. Three DWTs with ratios of winglet-height (b) to inner tube diameter (di) called blockage ratio (Rb) of 0.28, 0.35 and 0.42 were tested and their performance was compared to that of a longitudinal strip and plain tube under similar test flow conditions. Experiments were conducted over a wide range of flow rates, 3.35 × 10−5–8.33 × 10−5 m3/s, which correspond to 5500 ≤ Reynolds number (Re) ≤ 14,500 in the 14.3 mm i.d. tube. The results revealed that using DWTs dramatically increased the Nusselt number (Nu) by as much as 364.3% and the friction factor (f) by 15.5 times compared with those of a plain tube. Thermal performance (η) increased with a corresponding increase in Rb. The highest thermal performance (η) obtained was 1.4. Showing a notable improvement on the thermal performance of the system, DWTs are proposed as a favorable insert device. View Full-Text
Keywords: blockage ratio; delta winglet; vortex generator; friction factor; Nusselt number blockage ratio; delta winglet; vortex generator; friction factor; Nusselt number

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Yaningsih, I.; Wijayanta, A.T.; Miyazaki, T.; Koyama, S. Impact of Blockage Ratio on Thermal Performance of Delta-Winglet Vortex Generators. Appl. Sci. 2018, 8, 181.

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