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    Wyświetlanie 1-9 z 9
    Tytuł:
    Heat conduction in a finite medium using the fractional single-phase-lag model
    Autorzy:
    Siedlecka, Urszula
    Powiązania:
    https://bibliotekanauki.pl/articles/200748.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    single-phase-lagging heat conduction
    Caputo derivative
    fractional heat conduction
    przewodzenie ciepła
    Pochodna Caputo
    Opis:
    In the paper, a solution of the time-fractional single-phase-lagging heat conduction problem in finite regions is presented. The heat conduction equation with the Caputo time-derivative is complemented by the Robin boundary conditions. The Laplace transform with respect to the time variable and an expansion in the eigenfunctions series with respect to the space variable was applied. A method for the numerical inversion of the Laplace transforms was used. Formulation and solution of the problem cover the heat conduction in a finite slab, hollow cylinder and hollow sphere. The effect of the fractional order of the Caputo derivative and the phase-lag parameter on the temperature distribution in a slab has been numerically investigated.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 2; 401-407
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An analytical solution to the problem of time-fractional heat conduction in a composite sphere
    Autorzy:
    Kukla, S.
    Siedlecka, U.
    Powiązania:
    https://bibliotekanauki.pl/articles/202020.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat conduction
    multilayered sphere
    Caputo fractional derivative
    przewodzenie ciepła
    powłoka wielowarstwowa
    pochodna ułamkowego rzędu Caputo
    Opis:
    An analytical solution to the problem of time-fractional heat conduction in a sphere consisting of an inner solid sphere and concentric spherical layers is presented. In the heat conduction equation, the Caputo time-derivative of fractional order and the Robin boundary condition at the outer surface of the sphere are assumed. The spherical layers are characterized by different material properties and perfect thermal contact is assumed between the layers. The analytical solution to the problem of heat conduction in the sphere for time-dependent surrounding temperature and for time-space-dependent volumetric heat source is derived. Numerical examples are presented to show the effect of the harmonically varying intensity of the heat source and the harmonically varying surrounding temperature on the temperature in the sphere for different orders of the Caputo time-derivative.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2017, 65, 2; 179-186
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of non-Fourier thermal waves interaction in a solid material
    Autorzy:
    Lenarczyk, Marcin
    Domański, Roman
    Powiązania:
    https://bibliotekanauki.pl/articles/240472.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    non-Fourier equation
    heat waves
    hyperbolic heat conduction
    thermal wave interaction
    fale cieplne
    przewodzenie ciepła
    Opis:
    In this paper, effects of non-Fourier thermal wave interactions in a thin film have been investigated. The non-Fourier, hyperbolic heat conduction equation is solved, using finite difference method with an implicit scheme. Calculations have been carried out for three geometrical configurations with various film thicknesses. The boundary condition of a symmetrical temperature step-change on both sides has been used. Time history for the temperature distribution for each investigated case is presented. Processes of thermal wave propagation, temperature peak build-up and reverse wave front creation have been described. It has been shown that (i) significant temperature overshoot can appear in the film subjected to symmetric thermal load (which can be potentially dangerous for reallife application), and (ii) effect of temperature amplification decreases with increased film thickness.
    Źródło:
    Archives of Thermodynamics; 2019, 40, 1; 115-126
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes
    Autorzy:
    Taler, D.
    Taler, J.
    Kowal, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/240076.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    kotło parowe
    odwrotne przewodzenie ciepła
    strumień ciepła
    żużel
    heat flux meter
    inverse heat conduction problem
    slagging
    steam boiler
    Opis:
    The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surface of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.
    Źródło:
    Archives of Thermodynamics; 2011, 32, 1; 77-88
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A study on power losses of the 50 kVA SiC converter including reverse conduction phenomenon
    Autorzy:
    Rąbkowski, J.
    Płatek, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/201547.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    power losses
    three-phase converter
    MOSFET
    Schottky diode
    reverse conduction
    straty mocy
    konwerter trójfazowy
    dioda Schottky'ego
    odwrotne przewodzenie ciepła
    Opis:
    This paper deals with performance of the 50 kVA three-phase converter built with switches based on SiC MOSFET and anti-parallel Schottky diodes. In contrast to popular IGBT converters, a negative switch current is capable of flowing through the reverse conducting transistor, which results in different distribution of power losses among the devices. Thus, equations describing the conduction power losses of the transistor and diode are improved and verified by means of circuit simulations in Saber. Moreover, a comparison of power losses calculated with the use of standard and new equations is also shown. Total power losses in three SiC MOSFET modules of a 50 kVA converter operating at 20 kHz are up to 30% lower when reverse conduction is taken into account. This shows the importance of the discussed problem and proves that much better accuracy in the estimation of power losses and junction temperatures of SiC devices may be obtained with the proposed approach.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 4; 907-914
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of the possibility of determining the internal structure of composite material by estimating its thermal diffusivity
    Autorzy:
    Kucypera, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/240948.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    mathematical model
    direct problem
    inverse heat conduction problem
    composite material
    test stand
    model matematyczny
    zagadnienie proste
    odwrotne przewodzenie ciepła
    materiał kompozytowy
    stanowisko badawcze
    Opis:
    The aim of this paper is analysis of the possibility of determining the internal structure of the fibrous composite material by estimating its thermal diffusivity. A thermal diffusivity of the composite material was determined by applying inverse heat conduction method and measurement data. The idea of the proposed method depends on measuring the timedependent temperature distribution at selected points of the sample and identification of the thermal diffusivity by solving a transient inverse heat conduction problem. The investigated system which was used for the identification of thermal parameters consists of two cylindrical samples, in which transient temperature field is forced by the electric heater located between them. The temperature response of the system is measured in the chosen point of sample. One dimensional discrete mathematical model of the transient heat conduction within the investigated sample has been formulated based on the control volume method. The optimal dynamic filtration method as solution of the inverse problem has been applied to identify unknown diffusivity of multi-layered fibrous composite material. Next using this thermal diffusivity of the composite material its internal structure was determined. The chosen results have been presented in the paper.
    Źródło:
    Archives of Thermodynamics; 2014, 35, 1; 3-15
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical simulation of thermal phenomena and phase transformations in laser-arc hybrid welded joints
    Analiza numeryczna zjawisk cieplnych i przemian fazowych w połączeniach spawanych hybrydowo laser-łuk elektryczny
    Autorzy:
    Piekarska, W.
    Kubiak, M.
    Bokota, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/351334.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    spawanie laserowe
    przewodzenie ciepła
    przepływ płynów
    przemiany fazowe
    skład struktury
    analiza numeryczna
    laser-arc hybrid welding
    heat transfer
    fluid flow
    phase transformations
    structure composition
    numerical modeling
    Opis:
    The paper concerns mathematical and numerical modelling of temperature field with convective motion of liquid metal in the melted zone taken into account and numerical estimation of structure composition of a plate made of S355 steel, butt-welded by laser-arc hybrid welding technique. Coupled transport phenomena, including heat transfer and fluid flow in the melted zone, were described respectively by transient heat transfer equation with convective term and Navier-Stokes equation. Latent heat associated with the material's state changes and latent heat of phase transformations in solid state were taken into consideration in the solution algorithm. The kinetics of phase transformations and volumetric fractions of arising phases were calculated on the basis of the Johnson-Mehl-Avrami (JMA) and Koistinen-Marburger (KM) classic mathematical models. In modelling of phase transformations during heating continuous heating transformation (CHT) diagram was used, whereas continuous cooling transformation (CCT) diagram was used in modelling of phase transformations during cooling of welded steel. Transient heat transfer equation was solved using finite element method in Petrov-Galerkin formulation and Navier-Stokes equation was solved in Chorin's projection method. The solution algorithms were implemented in ObjectPascal programming language.
    Praca zawiera numeryczne modelowanie pola temperatury oraz prognozowanie numeryczne składu strukturalnego płaskownika wykonanego ze stali S355, spawanego doczołowo techniką hybrydową laser-łuk elektryczny. Model pola temperatury uwzględnia ruch ciekłego metalu w jeziorku spawalniczym. Sprzężone zjawiska transportu ciepła i cieczy w strefie przetopienia opisywane są rónaniem nieustalonego przewodzenia ciepła z członem konwekcyjnym i równaniem Naviera-Stokesa. W algorytmie numerycznym uwzględniono ciepła związane ze zmianą stanu skupienia materiału i ciepła przemian fazowych w stanie stałym. Kinetykę przemian fazowych w stanie stałym oraz algorytmy numeryczne wyznaczania ułamków objętościowych powstających faz oparto na równaniach Johnsona-Mehla-Avramiego (JMA) i Koistinena-Marburgera (KM). W modelowaniu przemian nagrzewania wykorzystano wykres ciągłego nagrzewania (CTPcA), natomiast w modelowaniu przemian chłodzenia wykorzystano spawalniczy wykres przemian austenitu (CTPc-S) spawanej stali. Do rozwiązania równania nieustalonego przewodzenia ciepła zastosowano metodę elementów skończonych w sformułowaniu Petrov-Galerkina, a równanie Naviera-Stokesa rozwiązano metodą projekcji Chorina. Algorytmy analizy rozważanych zagadnień zaimplementowano w języku programowania ObjectPascal.
    Źródło:
    Archives of Metallurgy and Materials; 2011, 56, 2; 409-421
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical study of heat conduction in the multi-disc brake integrated into the drive wheel AGV during braking
    Autorzy:
    Varecha, Daniel
    Kohár, Róbert
    Lukáč, Michal
    Powiązania:
    https://bibliotekanauki.pl/articles/2090734.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    simulation
    braking systems
    one-dimensional heat conduction
    multidisc brakes
    AGV
    organic brake pad
    ceramic brake pad
    symulacja
    układy hamulcowe
    przewodzenie ciepła jednowymiarowe
    hamulec wielotarczowy
    klocki hamulcowe ceramiczne
    klocki hamulcowe organiczne
    Opis:
    This paper is focused on the theoretical study of heat conduction in the multi-brake system of the automated guided vehicle (AGV). The study aims to compare the amount of heat generated during braking from 10 m/s until a stop in a brake system based on organic and ceramic friction material. The theoretical study of heat conduction is solved in Matlab computational software using a derived Fourier partial differential equation for nonstationary heat conduction. The results of the simulation of the heat conduction are shown in the diagrams and indicate not only the temperature dependence in the period during braking from a speed of 10 m/s to a stop but also the amount of heat accumulated in the steel disc during braking. The simulation results show that braking in both brake systems generates approximately the same amount of heat. The difference occurs in the period of thermal activity, which was influenced by the length of the braking distance. This is caused by a coefficient of friction that significantly affects the final braking result. Finally, it can be stated that the brake system based on organic material must be equipped with a steel disc with a minimum thickness of 8 mm. This is because the brake system based on organic friction material has a set temperature limit of 160 degrees Celsius. The results presented in this study will help an engineer constructor to choose the right procedures and parameters of geometry for designing the mentioned braking system for the considered AGV.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 2; e136718, 1--10
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical study of heat conduction in the multi-disc brake integrated into the drive wheel AGV during braking
    Autorzy:
    Varecha, Daniel
    Kohár, Róbert
    Lukáč, Michal
    Powiązania:
    https://bibliotekanauki.pl/articles/2173589.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    simulation
    braking systems
    one-dimensional heat conduction
    multidisc brakes
    AGV
    organic brake pad
    ceramic brake pad
    symulacja
    układy hamulcowe
    przewodzenie ciepła jednowymiarowe
    hamulec wielotarczowy
    klocki hamulcowe ceramiczne
    klocki hamulcowe organiczne
    Opis:
    This paper is focused on the theoretical study of heat conduction in the multi-brake system of the automated guided vehicle (AGV). The study aims to compare the amount of heat generated during braking from 10 m/s until a stop in a brake system based on organic and ceramic friction material. The theoretical study of heat conduction is solved in Matlab computational software using a derived Fourier partial differential equation for nonstationary heat conduction. The results of the simulation of the heat conduction are shown in the diagrams and indicate not only the temperature dependence in the period during braking from a speed of 10 m/s to a stop but also the amount of heat accumulated in the steel disc during braking. The simulation results show that braking in both brake systems generates approximately the same amount of heat. The difference occurs in the period of thermal activity, which was influenced by the length of the braking distance. This is caused by a coefficient of friction that significantly affects the final braking result. Finally, it can be stated that the brake system based on organic material must be equipped with a steel disc with a minimum thickness of 8 mm. This is because the brake system based on organic friction material has a set temperature limit of 160 degrees Celsius. The results presented in this study will help an engineer constructor to choose the right procedures and parameters of geometry for designing the mentioned braking system for the considered AGV.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 2; art. no. e136718
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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