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    Wyświetlanie 1-5 z 5
    Tytuł:
    Analysis of transient natural convective flow of a nanofluid in a vertical tube
    Autorzy:
    Jha, Basant K.
    Chitumu, Ali J.
    Oni, Michael O.
    Powiązania:
    https://bibliotekanauki.pl/articles/1839829.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    nanociecze
    naturalna konwekcja
    wymiana ciepła
    nanofluid
    transient
    natural convection
    heat transfer
    vertical tube
    Opis:
    An analysis into the transient natural convective flow of a nanofluid in a vertical tube is made. The governing equations of momentum, heat transfer and nanoparticle volume fraction are deduced, and the influence of the thermophoresis parameter and Brownian motion is incorporated. By direct integration and variation of the parameter, analytical solutions are obtained for flow formation and heat/mass transfer at steady-state. On the other hand, due to the complexity of same problem at transient state, a numerical solution is used to solve the discretized equations of motion using the implicit finite difference technique. The influence of the thermophoresis parameter and Brownian motion is noted and well discussed. For accuracy check, a numerical comparison is made between the steady state and transient state solution at large time; this comparison gives an excellent agreement. The role of various principal parameters on velocity profile, temperature, concentration of nanoparticles, Sherwood and Nusselt numbers are presented graphically and well discussed. It is noted that the buoyancy ratio decreases the fluid velocity significantly.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2021, 26, 2; 31-46
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner
    Autorzy:
    Rożeń, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/146233.pdf
    Data publikacji:
    2018
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    catalytic recombination
    computational fluid dynamics
    hydrogen safety
    natural convection
    rekombinacja katalityczna
    obliczeniowa dynamika płynów
    naturalna konwekcja
    Opis:
    Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear reactor (LWR). Inside a passive autocatalytic recombiner (PAR), hydrogen and oxygen molecules are adsorbed at catalyst active spots and they recombine to yield water. Heat released in this exothermic reaction creates natural convection of gas in the spaces between the elements supporting a catalyst. Hot and humid gas fl ows upwards into the PAR chimney, while fresh, hydrogen-rich gas enters the PAR from below. Catalytic recombination should start spontaneously at room temperature and low hydrogen concentration. Computational fl uid dynamics (CFD) has been used to study the dynamic behaviour of a plate-type Areva FR-380 recombiner in a quiescent environment for several test scenarios, including different rates of increase in hydrogen concentration and temporary catalyst deactivation. A method for the determination of pressure boundary conditions at the PAR exits was proposed and implemented into a CFD code. In this way, transient operation of PAR could be simulated without the need to model gas circulation outside the device. It was found that fi rst a slow downward fl ow of gas is developed, which may persist until the temperature of the catalyst foils rises. As soon as the gas inside the PAR absorbs enough heat to become lighter than the gas outside the PAR, it starts to fl ow upwards. Criteria for determining the start-up time of PAR were proposed. Model predictions were also compared with experimental data obtained in tests conducted at the THAI facility.
    Źródło:
    Nukleonika; 2018, 63, 2; 27-41
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermal analysis of a fully wet porous radial fin with natural convection and radiation using the spectral collocation method
    Autorzy:
    Khani, F.
    Darvishi, M. T.
    Gorla, R. S. R.
    Gireesha, B. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/264453.pdf
    Data publikacji:
    2016
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    porowatość
    naturalna konwekcja
    promieniowanie
    analiza termiczna
    wet porous radial fin
    natural convection
    radiation
    thermal analysis
    spectral collocation method
    Opis:
    Heat transfer with natural convection and radiation effect on a fully wet porous radial fin is considered. The radial velocity of the buoyancy driven flow at any radial location is obtained by applying Darcy’s law. The obtained non-dimensionalized ordinary differential equation involving three highly nonlinear terms is solved numerically with the spectral collocation method. In this approach, the dimensionless temperature is approximated by Chebyshev polynomials and discretized by Chebyshev-Gausse-Lobatto collocation points. A particular algorithm is used to reduce the nonlinearity of the conservation of energy equation. The present analysis characterizes the effect of ambient temperature in different ways and it provides a better picture regarding the effect of ambient temperature on the thermal performance of the fin. The profiles for temperature distributions and dimensionless base heat flow are obtained for different parameters which influence the heat transfer rate.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2016, 21, 2; 377-392
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of aspect ratio of enclosure on free convection from horizontal cylinders in Bingham plastic fluids
    Autorzy:
    Baranwal, Ashok Kumar
    Gupta, Anoop Kumar
    Tiwari, Anurag Kumar
    Melnik, Roderick
    Powiązania:
    https://bibliotekanauki.pl/articles/2173430.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Bingham plastic fluids
    aspect ratio
    Rayleigh number
    Nusselt number
    natural convection
    płyn plastikowy Bingham
    współczynnik proporcji
    liczba Rayleigha
    liczba Nusselta
    naturalna konwekcja
    Opis:
    Heat transfer in steady free convection from differentially heated cylinders enclosed in a rectangular duct filled with Bingham plastic fluids has been solved numerically for the ranges of the dimensionless groups as, Rayleigh number, 102 Ra 106; Prandtl number, 10 Pr 100 and, Bingham number, 0 Bn 50 for aspect ratios AR = 05, 0.6, 0.7, 0.8, 0.9 and 2. The streamlines, isotherm contours, yield surfaces, local and average Nusselt numbers were analysed and discussed. It is found that as the aspect ratio of the enclosure increases from 0.5 to 0.9, the average Nusselt number on the surface of the hot cylinder increases as a larger amount of fluid takes part in convection. Moreover, at sufficiently large Bingham numbers, yield stress forces dominate over buoyancy causing the flow to cease and thus the Nusselt number approaches its conduction limit. Finally, the Nusselt number approaches its conduction limit once the maximum Bingham number is reached.
    Źródło:
    Chemical and Process Engineering; 2022, 43, 2; 271--277
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    FEM simulation of triple diffusive natural convection along inclined plate in porous medium: prescribed surface heat, solute and nanoparticles flux
    Autorzy:
    Goyal, M.
    Goyal, R
    Bhargava, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/266289.pdf
    Data publikacji:
    2017
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    triple diffusive
    natural convection
    nanofluid
    binary base fluid
    porous medium
    solutal concentration flux
    nanoparticle concentration flux
    inclined plate
    naturalna konwekcja
    płyn bazowy
    nanocząstki
    Opis:
    In this paper, triple diffusive natural convection under Darcy flow over an inclined plate embedded in a porous medium saturated with a binary base fluid containing nanoparticles and two salts is studied. The model used for the nanofluid is the one which incorporates the effects of Brownian motion and thermophoresis. In addition, the thermal energy equations include regular diffusion and cross-diffusion terms. The vertical surface has the heat, mass and nanoparticle fluxes each prescribed as a power law function of the distance along the wall. The boundary layer equations are transformed into a set of ordinary differential equations with the help of group theory transformations. A wide range of parameter values are chosen to bring out the effect of buoyancy ratio, regular Lewis number and modified Dufour parameters of both salts and nanofluid parameters with varying angle of inclinations. The effects of parameters on the velocity, temperature, solutal and nanoparticles volume fraction profiles, as well as on the important parameters of heat and mass transfer, i.e., the reduced Nusselt, regular and nanofluid Sherwood numbers, are discussed. Such problems find application in extrusion of metals, polymers and ceramics, production of plastic films, insulation of wires and liquid packaging.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2017, 22, 4; 883--900
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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