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    Wyświetlanie 1-8 z 8
    Tytuł:
    Augmentation in heat transfer and friction of three sides over one side dimple roughened solar duct
    Autorzy:
    Kumar, Vikash
    Powiązania:
    https://bibliotekanauki.pl/articles/240256.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    dimple roughened
    relative roughness pitch
    relative roughness height
    dimple depth to diameter ratio
    nusselt number
    friction factor
    Opis:
    Providing roughness is an effective method to heat fluids to high temperature. Present paper make use of concave dimple roughness on one and three sides of roughened ducts aimed at determining rise in heat transfer and friction of three sides over one side roughened duct. Three sides roughened duct produces high heat transfer compared to one side roughened. Results are shown as a rise in Nusselt number and friction factor of three sides over one side roughened duct. Experimental investigation was conducted under actual outdoor condition at National Institute of Technology Jamshedpur, India to test various sets of roughened collectors. Roughness parameter varied as relative roughness pitch 8–15, relative roughness height 0.018–0.045, dimple depth to diameter ratio 1–2, Reynolds number 2500– 13500 at fixed aspect ratio (width/hight) 8. Highest enhancement in Nusselt number for varying relative roughness pitch, height, and diameter ratio was respectively found as 2.6 to 3.55 times, 1.91 to 3.42 times and 3.09 to 3.94 times compared to one side dimple roughened duct. Highest rise in friction for three sides over one side roughened duct for these varying parameters was respectively found as 1.62 to 2.79 times, 1.52 to 2.34 times and 2.21 to 2.56 times. To visualize the effect of roughness parameter on heat transfer and friction factor, variation in Nusselt number and friction factor for varying roughness parameters with Reynolds number is shown.
    Źródło:
    Archives of Thermodynamics; 2020, 41, 3; 57-89
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of the tool surface texture on friction and the surface layers properties of formed component
    Autorzy:
    Šugárová, Jana
    Šugár, Peter
    Frnčík, Martin
    Necpal, Martin
    Moravčíková, Jana
    Kusý, Martin
    Powiązania:
    https://bibliotekanauki.pl/articles/102207.pdf
    Data publikacji:
    2018
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    laser surface texture
    dimple shape
    dimple arrangement
    friction coefficient
    surface integrity
    tekstura powierzchni lasera
    kształt wgłębienia
    rozmieszczenie wgłębne
    współczynnik tarcia
    integralność powierzchni
    Opis:
    The morphological texturing of forming tool surfaces has a high potential to reduce friction and tool wear and also has an impact on the surface layers properties of formed material. In order to understand the effect of different types of tool textures, produced by nanosecond fibre laser, on the tribological conditions at the interface tool-formed material and on the integrity of formed part surface layers, the series of experimental investigations have been carried out. The coefficient of friction for different texture parameters (individual feature shape, including the depth profile of the cavities and orientation of the features relative to the material flow) was evaluated via a Ring Test and the surface layers integrity of the formed material (surface roughness and subsurface micro hardness) was also experimentally analysed. The results showed a positive effect of surface texturing on the friction coefficients and the strain hardening of test samples material. Application of surface texture consisting of dimple-like depressions arranged in radial layout contributed to the most significant friction reduction of about 40%. On the other hand, this surface texture contributed to the increase of surface roughness parameters, Ra parameter increased from 0.49 μm to 2.19 μm and the Rz parameter increased from 0.99 μm to 16.79 μm.
    Źródło:
    Advances in Science and Technology. Research Journal; 2018, 12, 1; 181-193
    2299-8624
    Pojawia się w:
    Advances in Science and Technology. Research Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Friction evaluation of laser textured tool steel surfaces
    Autorzy:
    Šugárová, J.
    Šugár, P.
    Frnčík, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/386955.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
    Tematy:
    laser surface texturing
    dimple-like depressions
    friction coefficient
    lubrication
    ring test
    Opis:
    Surface textures can be defined as a regularly arranged micro-depressions or grooves with defined shape and dimensions. These textures, if they are manufactured by laser ablation process, contribute to a significant improvement of the tribological, optical or various biological properties. The aim of this paper is to analyze the influence of the surface textures prepared by laser surface texturing (LST) at the friction coefficient value measured on the tool (90MnCrV8 steel) – workpiece (S235JRG1 steel) interface. Planar frontal surfaces of compression platens have been covered by parabolic dimple-like depressions with different dimensions. The morphological analysis of such manufactured depressions has been performed by laser scanning microscopy. Influence of such created textures on the tribological properties of the contact pair has been analyzed by the ring compression test method in the terms of hydrodynamic lubrication regime. The experimental research shown that by applying of surface textures with defined shape and dimensions and using an appropriate liquid lubricant at the same time, the coefficient of contact friction can be reduced nearly to the half of its original value.
    Źródło:
    Acta Mechanica et Automatica; 2017, 11, 2; 129-134
    1898-4088
    2300-5319
    Pojawia się w:
    Acta Mechanica et Automatica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fast Fourier Transform detection and reduction of high-frequency errors from the results of surface topography profile measurements of honed textures
    Autorzy:
    Podulka, Przemysław
    Powiązania:
    https://bibliotekanauki.pl/articles/1841821.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
    Tematy:
    surface topography
    measurement
    measurement errors
    measurement noise
    cylinder liner
    oil pockets
    dimple
    valley
    texture features
    Opis:
    In this paper, various type of noise detection procedures with surface topography profile analysis were proposed, compared (studied) and suggested. The honed cylinder liner surface textures with additionally burnished oil pockets were measured with a stylus or optical approaches. Measurement errors, defined as high-frequency measurement noise, were taken into sufficient consideration. It was proposed to select the noise detection methods more with profile (2D) than areal (3D) assessments; some-frequency noise was much easier to observe in profile than surface analysis. Moreover, applications of various type of regular filtration methods, mostly based on Gaussian functions, were compared with Fast Fourier Transform filtration for detection or reduction of some (high) frequency-defined measurement errors.
    Źródło:
    Eksploatacja i Niezawodność; 2021, 23, 1; 84-93
    1507-2711
    Pojawia się w:
    Eksploatacja i Niezawodność
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fretting-Wear Mechanism of Textured Surfaces
    Autorzy:
    Pashechko, Mykhaylo
    Marchuk, Volodymyr
    Kindrachuk, Myroslav
    Tisov, Oleksandr
    Kornienko, Anatolii
    Dukhota, Oleksandr
    Powiązania:
    https://bibliotekanauki.pl/articles/101973.pdf
    Data publikacji:
    2019
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    wear mechanism
    fretting
    wear products
    textured surface
    dimple
    mechanizm noszenia
    produkty noszenia
    teksturowane powierzchnie
    wgłębienie
    Opis:
    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.
    Źródło:
    Advances in Science and Technology. Research Journal; 2019, 13, 3; 186-191
    2299-8624
    Pojawia się w:
    Advances in Science and Technology. Research Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Flow and heat transfer characteristics of a novel airfoil-based tube with dimples
    Autorzy:
    Pei, Houju
    Liu, Meinan
    Yang, Kaijie
    Zhimao, Li
    Liu, Chao
    Powiązania:
    https://bibliotekanauki.pl/articles/2173696.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat transfer enhancement
    airfoil-based tube
    dimple
    comprehensive performance
    wzmocnienie wymiany ciepła
    rura
    wgłębienie
    wykonanie kompleksowe
    Opis:
    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.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2022, 70, 4; art. no. e141984
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical investigation of root canal irrigation adopting innovative needles with dimple and protrusion
    Autorzy:
    Li, P.
    Zhang, D.
    Xie, Y.
    Lan, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/307257.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dimple
    protrusion
    innovative needles
    numerical simulation
    passive flow control methods
    root canal irrigation
    wychylenie zębów
    symulacja komputerowa
    kanał zębowy
    Opis:
    As important passive flow control methods, dimples and protrusions have been successfully implemented via geometric modifications to manipulate flow fields to get a desired flow parameters enhancement. In this research, two novel needles were proposed based on a prototype by means of the dimple and protrusion, and flow patterns within a root canal during final irrigation with these needles were numerically investigated. The calculation cases consistent with the clinically realistic irrigant flow rates, which are 0.02, 0.16 and 0.26 mL s–1 are marked as case A, B and C, respectively. The characteristic parameters to estimate irrigation efficiency, such as shearing effect, mean apical pressure, irrigation replacement and fluid agitation, were compared and the optimal geometry in every calculation case was obtained. As shown from the results, flow rates and needle geometries were the causes of irrigation parameters variations. The sum of shear stress, irrigation replacement and fluid agitation were equal in the low flow rate case A, however, the needle with a protrusion on its tip had advantages in the three irrigation characteristic parameters above in calculation case B, and the needle with a dimple on its tip had advantages in calculation case C. Furthermore, the needles proposed did not give rise to the risk of irrigant extrusion. These needles can be better choices at larger flow rates. Therefore, needle geometry optimizations utilizing passive flow control methods are worthy to be investigated in the root canal irrigation enhancement.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2013, 15, 1; 43-50
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Development of measurement apparatus of piston assembly friction in a small motorcycle engine
    Autorzy:
    Nakashima, Kohei
    Matsunaga, Kota
    Uchiyama, Yosuke
    Yoshida, Masao
    Powiązania:
    https://bibliotekanauki.pl/articles/24202471.pdf
    Data publikacji:
    2023
    Wydawca:
    Polskie Towarzystwo Naukowe Silników Spalinowych
    Tematy:
    piston assembly friction
    floating cylinder liner
    piston
    fine particle bombarding
    micro dimple
    tarcie układu korbowego
    pływające tuleje cylindrowe
    tłok
    bombardowanie cząsteczkami
    Opis:
    This study developed a friction measurement apparatus with a floating cylinder liner in a small motorcycle engine. In this measurement apparatus, joint plates were installed in the grooves on the outer periphery of the floating liner, and then the plates, as well as load washers of piezo type, were mounted in the cylinder block at both the thrust and the anti-thrust sides. A stepped ring, protruding inward, was mounted on the top of the floating liner so that cylinder pressure acting on the stepped portion was balanced in the vertical direction. Thus, it was possible to measure the friction in the sliding directions of the piston. Using this apparatus, the effect of the engine operating period on friction was investigated in a piston micro-dimpled with a fine particle bombarding process. Results indicated that, at low engine speeds, friction decreased with the operating period, but at high engine speeds, friction decreased after 10 hours of operation, and then increased after 20 hours of operation.
    Źródło:
    Combustion Engines; 2023, 62, 3; 32--37
    2300-9896
    2658-1442
    Pojawia się w:
    Combustion Engines
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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