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Flow and heat transfer characteristics of a novel airfoil-based tube with dimples

Pei Houju, Liu Meinan, Yang Kaijie, Zhimao Li, Liu Chao

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 4

art. no. e141984

EN

The performance of a novel airfoil-based tube with dimples is numerically studied in the present work. The effect of Reynolds number Re, dimples number N, relative depth H/D, and cross-distribution angle α on flow and heat transfer characteristics are discussed for Re in the range between 7,753 and 21,736. The velocity contour, temperature contour, and local streamlines are also presented to get an insight into the heat transfer enhancement mechanisms. The results show that both the velocity magnitude and flow direction change, and fluid dynamic vortexes are generated around the dimples, which intensify the flow mixing and interrupt the boundary layer, resulting in a better heat transfer performance accompanied by a certain pressure loss compared with the plain tube. The Nusselt number Nu of the airfoil-based tube increases with the increase of dimples number, relative depth, and Reynolds numbers, but the effect of cross-distribution angle can be ignored. Under geometric parameters considered, the airfoil-based tube with N = 6, H/D = 0.1, α = 0° and Re = 7,753 can obtain the largest average PEC value 1.23. Further, the empirical formulas for Nusselt number Nu and friction factor f are fitted in terms of dimple number N, relative depth H/D, and Reynolds number Re, respectively, with the errors within ± 5%. It is found that the airfoil-based tube with dimples has a good comprehensive performance.

2

Fretting-Wear Mechanism of Textured Surfaces

Pashechko Mykhaylo, Marchuk Volodymyr, Kindrachuk Myroslav, Tisov Oleksandr, Kornienko Anatolii, Dukhota Oleksandr

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 3

186--191

EN

The wear mechanism of textured dimpled in conditions of lubricated fretting-wear is established, which, in contrast to others, takes into account possibility of removing deterioration products out of tribo-contact areas into dimples, preventing their action as abrasive material. Selection of optimal structural parameters of selectively dimpled areas allows to reduce duration of tribological couple running-in time. Depending on texture type, friction coefficient was reduced from 0.27 (for untreated furface) to 0.18, and wear loss – from 7.8 ×10–3g to 3.3 ×10–3g.

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Sound Absorption Properties Of Single-Hole Hollow Polyester Fiber Reinforced Hydrogenated Carboxyl Nitrile Rubber Composites

Jie H., Sheng J., Xiong Y.

Autex Research Journal

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2017

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Vol. 17, no. 3

263--267

EN

A series of single-hole hollow polyester fiber (SHHPF) reinforced hydrogenated carboxyl nitrile rubber (HXNBR) composites were fabricated. In this study, the sound absorption property of the HXNBR/SHHPF composite was tested in an impedance tube, the composite morphology was characterized by scanning electron microscope (SEM), and the tensile mechanical property was measured by strength tester. The results demonstrated that a remarkable change in sound absorption can be observed by increasing the SHHPF content from 0% to 40%. In the composite with 40% SHHPF in 1 mm thickness, the sound absorption coefficient reached 0.671 at 2,500 Hz; the effective bandwidth was 1,800-2,500 Hz for sound absorption coefficient larger than 0.2. But the sound absorption property of the composite deteriorated when the SHHPF content increased to 50% in 1 mm thickness. While with 20% SHHPF proportion, the sound absorption property was improved by increasing the thickness of composites from 1 to 5 mm. Compared with the pure HXNBR of the same thickness, the tensile mechanical property of the composite improved significantly by increasing the SHHPF proportion. As a lightweight composite with excellent sound absorption property, the HXNBR/SHHPF composite has potential practical application value in the fields of engineering.

4

Porównawcza miara dynamicznej twardości metali

Kolenda J., Kyzioł L.

Zeszyty Naukowe Akademii Marynarki Wojennej

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2007

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R. 48 nr 3 (170)

39-45

PL

Artykuł dotyczy oszacowania dynamicznej twardości metali na podstawie badań przy użyciu wgłębnika. Jako porównawczą miarę tej właściwości zaproponowano wartości ilorazu energii kinetycznej młota i objętości wgłębienia. Zdefiniowano warunki pomiarów.

EN

A comparative measure of dynamic hardness of metalsThe paper deals with the assessment of dynamic hardness of metals on the basis of tests conducted with an indenter. As a comparative measure of this property, the dynamic indentation hardness is proposed which can be evaluated as the ratio of kinetic energy of the hammer and the indentation volume. The conditions of reliable measurements are defined.

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Analiza cech geometrycznych nasion gryki pod kątem określenia kształtu i wymiarów wgłębień tryjera cylindrycznego

Kaliniewicz Z., Rawa T.

Problemy Inżynierii Rolniczej

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2001

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R. 9, nr 1

21-28

PL

Z analizy wynika, że modelem geometrycznym nasion gryki, może być symetryczna trójścienna bryła o jednakowym zaokrągleniu i jednakowej szerokości ścian. Geometria i wymiary w podstawowej wersji wgłębień, dostosowanej do czyszczenia całego zakresu wymiarowego nasion gryki, mogą być prostym odwzorowaniem przepołowionego wzdłuż modelu nasiona o wymiarach odpowiadających malsymalnym wymiarom nasion gryki. Nowe wgłębienia wykonane w płaszczu cylindra, odwzorowane od cech geometrycznych nasion frakcji krótkiej, powinny przyczynić się do poprawy skuteczności czyszczenia.

EN

A complex analysis of geometrical traits of buckwheat seeds was carried out. The analysis showed that the geometrical model of buckwheat seeds may be a symmetrical trihedral solid characterized by an equal rounding and equal width of all its walls. The geometry and dimensions in the primary version of pits adapted to the whole dimensional range of buckwheat seeds can be a simple projection of a grain model halved lengthwise. the projection of the pits from geometrical traits of short fraction seeds should conrtibute to improving the efficiency of buckwheat seed cleaning.