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Appl. Sci. 2018, 8(2), 181; doi:10.3390/app8020181

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

1
Department of Energy and Environmental Engineering, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga-shi, Fukuoka 816-8580, Japan
2
Department of Mechanical Engineering, Faculty of Engineering, Sebelas Maret University, Jl. Ir. Sutami 36 A, Surakarta 57126, Indonesia
3
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)
View Full-Text   |   Download PDF [2885 KB, uploaded 26 January 2018]   |  

Abstract

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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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

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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