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    Wyświetlanie 1-6 z 6
    Tytuł:
    Modelling of influence of turbulent transition on heat transfer conditions
    Autorzy:
    Bochon, K.
    Wróblewski, W.
    Dykas, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1943251.pdf
    Data publikacji:
    2008
    Wydawca:
    Politechnika Gdańska
    Tematy:
    laminar-turbulent transition
    Conjugate Heat Transfer (CHT)
    computational fluid dynamics CFD
    Opis:
    This article deals with the turbulent transition phenomenon modelling and its influence on heat transfer. The purpose of the analyses was to verify the transition modelling implemented in the ANSYS CFX 11 commercial code for popular test cases (low flow speed) described in literature, and then use it for verification of the in-house CFD code (created for compressible flows). The inhouse CFD code has been extended lately for the Conjugate Heat Transfer modelling (CHT) as well, taking into account important flow effects, especially the turbulent transition. A Wilcox k-omega turbulence model with the Low-Reynolds modification was used in the in-house code. The calculations in ANSYS CFX were made using an SST turbulence model and a gamma-theta transition model. A fully turbulent flow was modelled by means of both codes, and the results were compared with the available experimental data. Then, the turbulent transition for several test cases was analysed with ANSYS CFX. Afterwards, the in-house CFD code was verified by means of ANSYS CFX for a higher flow speed (Mach numbers). The CHT modelling was analysed by means of both codes and the results were compared and discussed. The conducted analyses show that the results obtained by means of both codes are comparable, but the turbulence model used in the in-house CFD code is simpler and requires less computation time. A modification of two equations turbulence models can be an alternative for design problems in more developed laminar/turbulent flows.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2008, 12, 3-4; 173-184
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermally Induced Polymorphic Transformation of Hexanitrohexaazaisowurtzitane (HNIW) Investigated by in-situ X-ray Powder Diffraction
    Autorzy:
    Liu, Y.
    Li, S.
    Wang, Z.
    Xu, J.
    Sun, J.
    Huang, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/358065.pdf
    Data publikacji:
    2016
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
    Tematy:
    HNIW
    polymorphism
    in situ X-ray diffraction
    phase transition
    heat stimulation
    Opis:
    The ε→γ phase transition of HNIW induced by heat was investigated with in situ X-ray powder diffraction (PXRD). The effects of purity, particle size, insensitive additives and the time of isothermal heat treatment on the phase transition were evaluated. It was found that the phase transition is irreversible with changes in temperature, and the two phases can coexist in a certain temperature range. Moreover, the initial phase transition temperature increases with increasing purity and decreasing particle size of HNIW, and thus with the approximate crystal density. The addition of graphite and paraffin wax to HNIW as insensitive additives leads to a decrease in the initial phase transition temperature, but the addition of TATB does not affect the initial phase transition temperature. Thus, TATB is a suitable insensitive additive. Moreover, at the critical temperature, the isothermal time determined the efficiency of the ε- to γ-phase transition. This work lays the foundations for the choice of molding technologies, performance test methods, ammunition storage options, as well as the manufacture of HNIW-based explosive formulations.
    Źródło:
    Central European Journal of Energetic Materials; 2016, 13, 4; 1023-1037
    1733-7178
    Pojawia się w:
    Central European Journal of Energetic Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The results of the experimental research of the heat transfer coefficient during steam condensation in the tubes of the diesel radiator sections
    Rezultaty ehksperimenthykh issledovanijj koehfficienta teplootdanykh pri kondensacii para v trubkakh teplovoznykh radiatornykh sekcijj
    Autorzy:
    Sklifus, Y.
    Mohyla, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/792234.pdf
    Data publikacji:
    2012
    Wydawca:
    Komisja Motoryzacji i Energetyki Rolnictwa
    Tematy:
    experimental research
    heat transfer coefficient
    heat transfer ratio
    diesel locomotive
    phase transition
    cooling system
    power plant
    steam condensation
    Źródło:
    Teka Komisji Motoryzacji i Energetyki Rolnictwa; 2012, 12, 4
    1641-7739
    Pojawia się w:
    Teka Komisji Motoryzacji i Energetyki Rolnictwa
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    NWA 6255 meteorite − Thermophysical properties of interior and the crust
    Autorzy:
    Łuszczek, K.
    Wach, R. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/411502.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Meteorytowe
    Tematy:
    NWA 6255
    DSC
    thermophysical properties of meteorite
    specific heat capacity
    troilite phase transition
    troilite cosmothermometer
    Opis:
    Differences in the thermophysical properties of NWA 6255 meteorite samples obtained from various locations with respect o the distance from the surface of the meteorite were evaluated by a differential scanning calorimetry (DSC). DSC is a perfect tool to experimentally verify theoretically predicted thermophysical properties of extraterrestrial matter. The specific heat capacity of the crust and the interior of meteorite were determined to be in the temperature range of 223‒823 K. Measured Cp values at room temperature for crust and for the interior of this meteorite were 602 and 668 J·kg–1·K–1, respectively. In addition, the phase transition of troilite from: (a) the fusion crust samples, (b) the edge part of the meteorite (1‒2 mm below the crust), and (c) the interior (over 10 mm below the fusion crust) was examined. It is shown that the shift of α/β transition peak of the troilite exhibits the temperature gradient evolved during atmospheric passage of a meteoroid. Moreover, the enthalpy changes of α/β transition were used to determine the troilite content in the meteorite samples (3.6 wt.%). Obtained data are in agreement with previous Leco method’s results, since NWA 6255 is relatively fresh find (W1) and troilite tends to oxidized quickly.
    Źródło:
    Meteorites; 2014, 3, No. 1-2; 33-44
    2299-0313
    2299-1220
    Pojawia się w:
    Meteorites
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of turbulence model, turbulence length scale and wall roughness on the laminar-turbulence transition and temperature distribution of a convectively cooled C3X turbine vane
    Autorzy:
    Banaś, K.
    Badur, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/175460.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    laminar-turbulent transition
    conjugate heat transfer analysis of turbine
    C3X turbine vane
    roughness correction
    Opis:
    Our paper demonstrates the ability of Favre-averaged Navier–Stokes (FANS) turbulence models to predict the laminar-turbulent transition and shows the influence of the models on the wall temperature distribution. The investigations were based on conjugate heat transfer analyses of a convectively cooled C3X turbine vane, which were performed using commercial flow simulation software. We compared several eddy-viscosity models: shear stress transport (SST), γ-Reθ SSTtransition, v2-f, k-ε, realizable, k-kl-ω transition, and second-order closure ε-based Reynolds stress model (RSM) with a linear pressure-strain model. The turbulence length scale (TLS) was not measured during the experiment, so its influence on the location of the transition onset and wall temperature distribution is presented. We also examined the influence of the roughness of the airfoil wall on the location of turbulence initialization and the wall temperature distribution.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2017, 138; 13-32
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical investigation on the transition of fluid flow characteristics through a rotating curved duct
    Autorzy:
    Hasan, Mohammad Sanjeed
    Islam, MD. Sirajul
    Badsha, MD. Faisal
    Mondal, Rabindra Nath
    Lorenzini, Giulio
    Powiązania:
    https://bibliotekanauki.pl/articles/1839803.pdf
    Data publikacji:
    2020
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    wymiana ciepła
    przepływ wtórny
    liczba Taylora
    rotating curved duct
    Taylor number
    flow transition
    secondary flow
    heat transfer
    Opis:
    Time-dependent flow investigation through rotating curved ducts is utilized immensely in rotating machinery and metal industry. In the ongoing exploration, time-dependent solutions with flow transition through a rotating curved square duct of curvature ratio 0.009 have been performed. Numerical calculations are carried out for constant pressure gradient force, the Dean number Dn = 1000 and the Grashof number Gr = 100 over a wide range of the Taylor number values […] for both positive and negative rotation of the duct. The software Code:Blocks has been employed as the second programming tool to obtain numerical solutions. First, time evolution calculations of the unsteady solutions have been performed for positive rotation. To clearly understand the characteristics of regular and irregular oscillations, phase spaces of the time evolution results have been enumerated. Then the calculations have been further attempted for negative rotation and it is found that the unsteady flow shows different flow instabilities if Tr is increased or decreased in the positive or in the negative direction. Two types of flow velocities such as axial flow and secondary flow and temperature profiles have been exposed, and it is found that there appear two- to four-vortex asymmetric solutions for the oscillating flows for both positive and negative rotation whereas only two-vortex for the steady-state solution for positive rotation but four-vortex for negative rotation. From the axial flow pattern, it is observed that two high-velocity regions have been created for the oscillating flows. As a consequence of the change of flow velocity with respect to time, the fluid flow is mixed up in a great deal which enhances heat transfer in the fluid.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2020, 25, 3; 45-63
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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