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    Wyświetlanie 1-17 z 17
    Tytuł:
    Vertical heat transport at infinite Prandtl number for micropolar fluid
    Autorzy:
    Caggio, M.
    Kalita, P.
    Łukaszewicz, G.
    Mizerski, K. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/38611128.pdf
    Data publikacji:
    2020
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    micropolar fluid
    Rayleigh–Benard convection
    heat transport
    Rayleigh number
    Prandtl number
    Nusselt number
    Opis:
    We investigate the upper bound on the vertical heat transport in the fully 3D Rayleigh–Bénard convection problem at the infinite Prandtl number for a micropolar fluid. We obtain a bound, given by the cube root of the Rayleigh number, with a logarithmic correction. The derived bound is compared with the optimal known one for the Newtonian fluid. It follows that the (optimal) upper bound for the micropolar fluid is less than the corresponding bound for the Newtonian fluid at the same Rayleigh number. Moreover, strong microrotational diffusion effects can entirely suppress the heat transfer. In the Newtonian limit our purely analytical findings fully agree with estimates and scaling laws obtained from previous theories significantly relying on phenomenology.
    Źródło:
    Archives of Mechanics; 2020, 72, 6; 525-553
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the onset of thermal instability of a porous medium layer saturating a Jeffrey nanofluid
    Autorzy:
    Rana, Gian C.
    Gautam, Poonam Kumari
    Powiązania:
    https://bibliotekanauki.pl/articles/38883772.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    nanofluid
    Jeffrey model
    Rayleigh number
    porous medium
    convection
    Opis:
    The onset of stationary convection in thermal instability of porous layer saturating a Jeffrey nanofluid is studied. The behaviour of nanofluid is described by a Jeffrey fluid model and the porous layer is assumed to follow Darcy’s law. Due to the presence of the Jeffrey parameter and nanoparticles, the momentum-balance equation of fluid is modified. The linear stability analysis and normal modes analysis method are utilised to derive the dispersion relation for the Rayleigh number in terms of various parameters for free-free boundaries. The effects of the Jeffrey parameter, Lewis number, modified diffusivity ratio, nanoparticles’ Rayleigh number and medium porosity on the physical system are discussed analytically and graphically.
    Źródło:
    Engineering Transactions; 2022, 70, 2; 123-139
    0867-888X
    Pojawia się w:
    Engineering Transactions
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Anisotropic turbulent viscosity and large-scale motive force in thermally driven turbulence at low Prandtl number
    Autorzy:
    Mizerski, K. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/38695701.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    thermal convection
    heat transport
    Rayleigh number
    Prandtl number
    random heat source
    Opis:
    The fully developed turbulent Boussinesq convection is known to form large-scale rolls, often termed the ‘large-scale circulation’ (LSC). It is an interesting question how such a large-scale flow is created, in particular in systems when the energy input occurs at small scales, when inverse cascade is required in order to transfer energy into the large-scale modes. Here, the small-scale driving is introduced through stochastic, randomly distributed heat source (say radiational). The mean flow equations are derived by means of simplified renormalization group technique, which can be termed a ‘weakly nonlinear renormalization procedure’ based on consideration of only the leading order terms at each step of the recursion procedure, as full renormalization in the studied anisotropic case turns out unattainable. The effective, anisotropic viscosity is obtained and it is shown that the inverse energy cascade occurs via an effective ‘motive force’ which takes the form of transient negative, vertical diffusion.
    Źródło:
    Archives of Mechanics; 2022, 74, 5; 409-436
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermal convection in a ferromagnetic fluid layer with magnetic field dependent viscosity: a correction applied
    Autorzy:
    Prakash, J.
    Kumar, R.
    Kumari, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/178325.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    ferromagnetic convection
    magnetic field dependent viscosity
    stationary convection
    Rayleigh number
    Opis:
    The effect of magnetic field dependent (MFD) viscosity on thermal convection in a horizontal ferromagnetic fluid layer has been investigated numerically. A correction is applied to Sunil et al. [24] which is very important in order to predict the correct behavior of MFD viscosity. Linear stability analysis has been carried out for stationary convection. The MFD viscosity parameter δ as well as the measure of nonlinearity of magnetization M3, both have a stabilizing effect on the system. Numerical results are also obtained for large values of magnetic parameter M1 and predicted graphically.
    Źródło:
    Studia Geotechnica et Mechanica; 2017, 39, 3; 39-46
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental tests for the occurence of convective heat transfer within the bed of rectangular steel profiles
    Autorzy:
    Wyczółkowski, R.
    Musiał, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/239990.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    konwekcja swobodna
    liczbia Rayleigha
    free convection
    Rayleigh number
    rectangular sections
    Opis:
    The paper describes tests intended to examine the occurrence of natural convection within the space occupied by 40x20 mm rectangular steel sections. Within these tests the bed of four layers of section was heated by the electric palate heater. Depending on the manner in which the heater was positioned, the tests were divided into two series. In the case of heating from above, the heat flowing through the bed is transferred only by conduction and radiation. When heating the bed from below, in addition to conduction and radiation, also a convective heat transfer will occur. Should this be the case, it will result in the intensification of the heat exchange. The results of measurements carried out have not demonstrated that the occurrence of any possible natural convection would influence the development of a temperature field in this type of charge.
    Źródło:
    Archives of Thermodynamics; 2012, 33, 3; 89-100
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The heat transfer and flow structure analyses of low concentration copper nanofluids in a strong magnetic field
    Autorzy:
    Roszko, A.
    Fornalik-Wajs, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/175547.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    nanofluids
    heat transfer
    flow structure
    fast Fourier transform
    Nusselt number ratio
    thermomagnetic Rayleigh number
    Opis:
    Main aim of this paper was to analyze the influence of strong magnetic field on the enhancement or suppression of nanofluids transport processes. The second objective was to determine how the flow structure changed under the influence of a magnetic field. Analyzed diamagnetic nanofluids composed of distilled water and the copper nanoparticles of 40–60 nm size in three different concentrations (50, 500, and 1000 ppm). The experimental enclosure position in the magnet test section caused the most intricate interaction of the acting forces: the gravitational and magnetic buoyancy ones, and made the interpretation of results very difficult. The Nusselt number ratio and the thermomagnetic Rayleigh number were determined for heat transfer analysis, while the fast Fourier transform was performed for the nanofluid flow structure analysis. Spectral analysis for all examined nanofluids was presented. Influence of nanoparticles concentration was clearly visible, while the direct impact of magnetic field on the heat transfer and flow structure should be still investigated.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2015, 128; 29-42
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electro-hydrodynamic convection in a rotating dielectric micropolar fluid layer
    Autorzy:
    Kaur, H.
    Verma, G. N.
    Powiązania:
    https://bibliotekanauki.pl/articles/264654.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    konwekcja
    liczba Rayleigha
    liczba Taylora
    convection
    rotation
    electric
    Rayleigh number
    Taylor number
    normal mode
    Opis:
    Thermal convection of a rotating dielectric micropolar fluid layer under the action of an electric field and temperature gradient has been investigated. The dispersion relation has been derived using normal mode analysis. The effects of the electric Rayleigh number, micropolar viscosity, Taylor number and Prandtl number on stability and over stability criteria are discussed. It is found that rotation postpones the instability in the fluid layer, while the Prandtl number and rotation both have a stabilizing effect. It is also observed that the micropolar fluid additives have a stabilizing effect, whereas the electric field has a destabilizing effect on the onset of convection stability.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2019, 24, 4; 106-124
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical solution of natural convective heat transfer under magnetic field effect
    Autorzy:
    Şahin, Serpil
    Demir, Hüseyin
    Powiązania:
    https://bibliotekanauki.pl/articles/387646.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
    Tematy:
    natural convection heat transfer
    rayleigh number
    chandrasekhar number
    pseudo time derivative
    newtonian fluid
    pseudoplastic fluid
    Opis:
    In this study, non-Newtonian pseudoplastic fluid flow equations for 2-D steady, incompressible, the natural convective heat transfer are solved numerically by pseudo time derivative. The stability properties of natural convective heat transfer in an enclosed cavity region heated from below under magnetic field effect are investigated depending on the Rayleigh and Chandrasekhar numbers. Stability properties are studied, in particular, for the Rayleigh number from 10[indeks górny]4 to 10[indeks górny]6 and for the Chandrasekhar number 3, 5 and 10. As a result, when Rayleigh number is bigger than 10[indeks górny]6 and Chandrasekhar number is bigger than 10, the instability occurs in the flow domain. The results obtained for natural convective heat transfer problem are shown in the figures for Newtonian and pseudoplastic fluids. Finally, the local Nusselt number is evaluated along the bottom wall.
    Źródło:
    Acta Mechanica et Automatica; 2019, 13, 1; 23-29
    1898-4088
    2300-5319
    Pojawia się w:
    Acta Mechanica et Automatica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Variable gravity effects on thermal instability of nanofluid in anisotropic porous medium
    Autorzy:
    Chand, R.
    Rana, G. C.
    Kumar, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/265426.pdf
    Data publikacji:
    2013
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    porowatość
    liczba Rayleigha
    zmienna grawitacja
    nanofluid
    anisotropic porous medium
    Rayleigh number
    variable gravity
    Opis:
    In this paper, we study the effects of variable gravity on thermal instability in a horizontal layer of a nanofluid in an anisotropic porous medium. Darcy model been used for the porous medium. Also, it incorporates the effect of Brownian motion along with thermophoresis. The normal mode technique is used to find the confinement between two free boundaries. The expression of the Rayleigh number has been derived, and the effects of variable gravity and anisotropic parameters on the Rayleigh number have been presented graphically.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2013, 18, 3; 631-642
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Heat transfer by natural convection from a heated square inner cylinder to its elliptical outer enclosure utilizing nanofluids
    Autorzy:
    Bouras, Abdelkrim
    Taloub, Djedid
    Driss, Zied
    Debka, Siham
    Powiązania:
    https://bibliotekanauki.pl/articles/2174195.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    konwekcja naturalna
    nanociecz
    ułamek objętościowy
    natural convection
    Rayleigh number
    nanofluid
    volume fraction
    square elliptical
    Opis:
    In this paper a numerical study of natural convection of stationary laminar heat transfers in a horizontal ring between a heated square inner cylinder and a cold elliptical outer cylinder is presented. A Cu-water nanofluid flows through this annular space. Different values of the Rayleigh number and volume fraction of nanoparticles are studied. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method and on the Boussinesq approximation. The interior and exterior surfaces are kept at constant temperature. The study is carried out for Rayleigh numbers ranging from 310 to 510. We have studied the effects of different Rayleigh numbers and volume fraction of nanoparticles on natural convection. The results are presented as isotherms, isocurrents, and local and mean Nusselt numbers. The aim of this study is to study the influence of the thermal Rayleigh number and volume fraction of nanoparticles on the heat transfer rate.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2022, 27, 2; 22--34
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The onset of convection in a rotating multicomponent fluid layer
    Autorzy:
    Prakash, J.
    Singh, V.
    Kumar, R.
    Kumari, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/281283.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    multicomponent convection
    principle of exchange of stabilities
    oscillatory motions
    complex growth rate
    concentration Rayleigh number
    Lewis number
    Opis:
    The onset of convective instability is analysed in a rotating multicomponent fluid layer in which density depends on n stratifying agents (one of them is heat) having different diffusivities. Two problems have been analysed mathematically. In the first problem, a sufficient condition is derived for the validity of the principle of the exchange of stabilities. Further, when the complement of this condition holds good, oscillatory motions of neutral or growing amplitude can exist, and thus it is important to derive upper bounds for the complex growth rate of such motions when at least one of the bounding surfaces is rigid so that exact solutions of the problem in closed form are not obtainable. Thus, as the second problem, bounds for the complex growth rates are also obtained. Above results are uniformly valid for quite general nature of the bounding surfaces.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2016, 54, 2; 477-488
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of the Rayleigh number in the area of steel rectangular sections in the conditions of stedy and unstedy heat flow
    Analiza liczby Rayleigha w obszarze stalowych profili prostokątnych w warunkach ustalonego i nieustalonego przepływu ciepła
    Autorzy:
    Wyczółkowski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/395913.pdf
    Data publikacji:
    2014
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    Rayleigh number
    free convection
    steel section
    heat treatment
    liczba Rayleigha
    konwekcja swobodna
    profile stalowe
    obróbka cieplna
    Opis:
    The paper presents the experimental measurements dedicated to the research for the Rayleigh number (Ra) in the area of rectangular steel sections. This problem is associated with the analysis of the free convection which takes place in the heating of sections bundles during the heat treatment. The study was conducted for both steady and transient heat transfer. The values of the Ra number obtained for the tested sections allow to describe the phenomenon of convection on the basis of a very simple criterial dependence. It greatly simplifies the mathematical description of the heat transfer phenomenon in the concerned charges.
    W artykule przedstawiono wyniki badań eksperymentalnych, których celem było określonie liczby Rayleigha (Ra) dla profili prostokątnch, nagrzewanych w warunkach ustalonej i nieustalonej wymiany ciepła. Analizie poddano trzy rodzaje profili: 40x20 mm, 60x60 mm oraz 80x80 mm. Badania dla warunków ustalonych przeprowadzono w komorze grzewczej stanowiska do pomiarów efektywnej przewodności cieplnej wsadów porowatych. Natomiast badania w warunkach nieustalonych przeprowadzono w elektrycznym piecu komorowym. Charakter zmian liczby Ra w funkcji temperatury, dla obu sposobów nagrzewania jest podobny. W każdym z przypadków, maksymalną wartość parametr Ra uzyskuje w przedziale temperatury około 100200oC. Dla profili 80x80 mm parametr ten jest około sześciokrotnie większy w porównaniu z profilami 60x60 mm. W przypadku nieustalonego przepływu ciepła, bezwzględne wartości parametru Ra są o rząd wielkości większe od wartości uzyskanych dla warunków ustalonych. Odnotowane liczby Ra nie przekroczyły wartości 107. Maksymalna wartość tego parametru wyniosła około 1,2x106. Zatem przy nagrzewaniu analizowanych profili, występujacą w ich wnętrzu konwekcję, można traktować jako intensyfikację przewodzenia w wypełniającym je powietrzu. Wyniki przedstawionych badań posłużą do analizy wpływu występującej wewnątrz profili konwekcji, na proces nagrzewania wiązek tych elementów. Ostatecznym wynikiem prowadzonych w tym zakresie analiz, będzie opracowanie modelu do wyznaczania efektywnej przewodności cieplnej tego wsadu.
    Źródło:
    Civil and Environmental Engineering Reports; 2014, 14; 107-118
    2080-5187
    2450-8594
    Pojawia się w:
    Civil and Environmental Engineering Reports
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Rayleigh number on internal eccentricity in a heated horizontal elliptical cylinder to its coaxial square enclosure
    Autorzy:
    Bouras, Abdelkrim
    Taloub, Djedid
    Driss, Zied
    Powiązania:
    https://bibliotekanauki.pl/articles/1839785.pdf
    Data publikacji:
    2020
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    konwekcja naturalna
    płyn Newtona
    liczba Rayleigha
    natural convection
    newtonian fluid
    geometry ratio
    Rayleigh number
    elliptical cylinder
    Opis:
    This paper deals with numerical investigation of a natural convective flow in a horizontal annular space between a heated square inner cylinder and a cold elliptical outer cylinder with a Newtonian fluid. Uniform temperatures are imposed along walls of the enclosure. The governing equations of the problem were solved numerically by the commercial code Fluent, based on the finite volume method and the Boussinesq approximation. The effects of Geometry Ratio GR and Rayleigh numbers on fluid flow and heat transfer performance are investigated. The Rayleigh number is varied from 103 to 106. Throughout the study the relevant results are presented in terms of isotherms, and streamlines. From the results, we found that the increase in the Geometry Ratio B leads to an increase of the heat transfer coefficient. The heat transfer rate in the annulus is translated in terms of the average Nusselt numbers along the enclosure's sides. Tecplot 7 program was used to plot the curves which cleared these relations and isotherms and streamlines which illustrate the behavior of air through the channel and its variation with other parameters. The results for the streamlines, isotherms, local and average Nusselt numbers average Nusselt numbers are compared with previous works and show good agreement.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2020, 25, 3; 17-29
    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:
    A Numerical Study of Combined Natural and Marangoni Convection in a Square Cavity
    Autorzy:
    Cicek, K.
    Baytas, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/116928.pdf
    Data publikacji:
    2009
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    Numerical Study
    Square Cavity
    natural convection
    Marangoni Convection
    Buoyancy-Driven Flow
    Thermo Capillary Flow
    Navier-Stokes Equations
    Rayleigh Number
    Opis:
    Through the aim of this study, the effects of combined buoyancy-driven flows and thermo capillary flows, which are emerged from temperature differences, on fluid flow and heat transfer numerically investigated with differentially heated side walls in a free surface square cavity. The study has been accomplished with three milestones to achieve the right solutions. For every milestone Navier-Stokes, continuity and energy equations are discretized by using finite volume method and grids with 52 x 52 control volumes. Results are presented Pr=1, Pr=7 and Pr=100. The effect of positive and negative Marangoni number on fluid flow and heat transfer at different Rayleigh number are considered and discussed.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2009, 3, 2; 173-178
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of components effecting free convection intensity in steel rectangular sections
    Autorzy:
    Wyczółkowski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/240388.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    free convection
    Rayleigh number
    section bundles
    effective thermal conductivity
    heat treatment
    konwekcja swobodna
    liczbia Rayleigha
    efektywna przewodność cieplna
    obróbka cieplna
    Opis:
    Free convection is one of the heat transfer modes which occurs within the heat-treated bundles of steel rectangular section. A comprehensive study of this phenomenon is necessary for optimizing the heating process of this type of charge. The free convection intensity is represented by the Rayleigh number Ra. The value of this criterion depends on the following parameters: the mean section temperature, temperature difference within the section, kinematic coefficient of viscosity, volume expansion coefficient and the Prandtl number. The paper presents the analysis of the impact of these factors on free convection in steel rectangular sections. The starting point for this analysis were the results of experimental examinations. It was found that the highest intensity of this process occurs for the temperature of 100°C. This is mainly caused by changes in the temperature difference observed in the area of sections and changes in kinematic coefficient of viscosity of air. The increase in the value of the Rayleigh number criterion at the initial stage is attributable to changes in the parameter of temperature difference within the section. After exceeding 100°C, the main effect on convection is from changes in air viscosity. Thus, with further increase in temperature, the Rayleigh number starts to decline rapidly despite further rise in the difference in temperature.
    Źródło:
    Archives of Thermodynamics; 2015, 36, 3; 105-121
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Stability of Micropolar Fluid in a Porous Medium Provoked by Heat Function and Radiation
    Autorzy:
    Nwabuzor, P. O.
    Ngiangia, A. T.
    Chukwuocha, E. O.
    Powiązania:
    https://bibliotekanauki.pl/articles/1076558.pdf
    Data publikacji:
    2019
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Electroconductivity
    Heat Function
    Micropolar Fluid
    Rayleigh
    Stability
    Wave Number
    Opis:
    The stability of micropolar fluid flow in a channel under the influence of heat function, magnetic field and radiation was investigated. Using the similarity solution and non-dimensionalizing, the governing partial differential equations (PDEs) where transformed to a set of non-linear differential equations (ODEs). We therefore perturbed the system and determined the stability of the system. Wolfram 9 software (Mathematica) was used to analyze the various stability effect of the material parameters on the fluid flow. The graphical results reflects the expected physical behavior of the flow configuration under consideration. The study reveals that the Prandtl (Pr), wave (a), Radiation (R) and heat function parameters at a certain critical value of the wave number hastens the onset of stability. While the Electroconductivity (σ), Magnetic field (M), Micropolar (K) and Microrotational (λ) parameters delays the onset of stability. The result are in agreement with the works of other literature sited.
    Źródło:
    World Scientific News; 2019, 115; 174-192
    2392-2192
    Pojawia się w:
    World Scientific News
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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