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    Wyświetlanie 1-4 z 4
    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:
    Experimental and theoretical investigation of an evacuated tube solar water heater incorporating wickless heat pipes
    Autorzy:
    Al-Joboory, Hassan Naji Salman
    Powiązania:
    https://bibliotekanauki.pl/articles/240588.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    wickless heat pipe
    fill charge
    electrical analogy
    evacuated tube solar collector
    water heater
    performance
    Opis:
    The present work involved an extensive outdoor performance testing program of a solar water heating system that consists of four evacuated tube solar collectors incorporating four wickless heat pipes integrated to a storage tank. Tests were conducted under the weather conditions of Baghdad, Iraq. The heat pipes were of 22 mm diameter, 1800 mm evaporator length and 200 mm condenser length. Three heat pipe working fluids were employed, ethanol, methanol, and acetone at an inventory of 50% by volume of the heat pipe evaporator sections. The system was tested outdoors with various load conditions. Results showed that the system performance was not sensitive to the type of heat pipe working fluid employed here. Improved overall efficiency of the solar system was obtained with hot water withdrawal (load conditions) by 14%. A theoretical analysis was formulated for the solar system performance using an energy balance based iterative electrical analogy formulation to compare the experimental temperature behavior and energy output with theoretical predictions. Good agreement of 8% was obtained between theoretical and experimental values.
    Źródło:
    Archives of Thermodynamics; 2020, 41, 3; 3-31
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental research on separation efficiency of aerosol particles in vortex tube separators with electric field
    Autorzy:
    Dziubak, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/202024.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    vortex tube separator
    electric fields
    separation efficiency and filtration performance
    pressure drop across the cyclone separator
    experimental research
    Opis:
    A comparative analysis of filtration performance of tangential and axial inlet reverse-flow cyclone separators and vortex tube separators is presented. The study showed that vortex tube separators are characterized by a quality factor q several time higher than tangential inlet reverse-flow cyclone separators. The cyclone separators yield low separation efficiency and low filtration performance at low air flow rates at low air volumes aspired by the engine at low speed. One of the well-known and not commonly used methods to improve separation efficiency is to apply electric field. An original design of a vortex tube separator with insulators generating electric field in the area of aerosol flow is presented. High voltage was applied to the cyclone separator housing and its swirl vane. A special method and test conditions were developed for cyclone separators with electric field. Separation efficiency, filtration performance and pressure drop across the cyclone separator in two different variants were determined. The tests were carried out at five inlet velocity of cyclones υ0 = 1.75; 3.5; 7.0; 10.5; 14 m/s at an extraction rate of m0 = 10%, and at an average dust concentration in the inlet air of s = 1 g/m3. Using the electric field in the area of a swirling aerosol stream resulted in an increase (over 12% – φ c = 96.3%) in separation efficiency at inlet velocity of cyclone ranging from 1.75 to 3.5 m/s. An increase in separation efficiency at other inlet velocity of cyclone is minor and does not exceed 3‒4%.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2020, 68, 3; 503-516
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fractional order tube model reference adaptive control for a class of fractional order linear systems
    Autorzy:
    Balaska, Hanane
    Ladaci, Samir
    Djouambi, Abdelbaki
    Schulte, Horst
    Bourouba, Bachir
    Powiązania:
    https://bibliotekanauki.pl/articles/330930.pdf
    Data publikacji:
    2020
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    fractional order system
    linear system
    model reference adaptive control
    fractional adaptive control
    performance tube
    fractional order TMRAC
    system ułamkowego rzędu
    system liniowy
    sterowanie adaptacyjne
    Opis:
    We introduce a novel fractional order adaptive control design based on the tube model reference adaptive control (TMRAC) scheme for a class of fractional order linear systems. By considering an adaptive state feedback control configuration, the main idea is to replace the classical reference model with a single predetermined trajectory by a fractional order performance tube guidance model allowing a set of admissible trajectories. Besides, an optimization problem is formulated to compute an on-line correction control signal within specified bounds in order to update the system performance while minimizing a control cost criterion. The asymptotic stability of the closed loop fractional order control system is demonstrated using an extension of the Lyapunov direct method. The dynamical performance of the fractional order tube model reference adaptive control (FOTMRAC) is compared with the standard fractional order model reference adaptive control (FOMRAC) strategy, and the simulation results show the effectiveness of the proposed control method.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2020, 30, 3; 501-515
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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