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Wyświetlanie 1-15 z 41
Tytuł:
Natural and mixed convection of a nanofluid in porous cavities: critical analysis using buongiorno’s model
Autorzy:
Zahmatkesh, Iman
Habibi, Mohammad Reza
Powiązania:
https://bibliotekanauki.pl/articles/279435.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
natural convection
mixed convection
nanofluid
porous media
Buongiorno’s model
Opis:
In this paper, Buongiorno’s mathematical model is adopted to simulate both natural convection and mixed convection of a nanofluid in square porous cavities. The model takes into account the Brownian diffusion and thermophoresis effects. Both constant and variable temperatures are prescribed at the side walls while the remaining walls are maintained adiabatic. Moreover, all boundaries are assumed to be impermeable to the base fluid and the nanoparticles. The governing equations are transformed to a form of dimensionless equations and then solved numerically using the finite-volume method. Thereafter, effects of the Brownian diffusion parameter, the thermophoresis number, and the buoyancy ratio on the flow strength and the average Nusselt number as well as distributions of isocontours of the stream function, temperature, and nanoparticles fraction are presented and discussed.
Źródło:
Journal of Theoretical and Applied Mechanics; 2019, 57, 1; 221-233
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
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:
Natural convection in a partially heated cylinder: A numerical study
Autorzy:
Núñez, José
Beltrán, Alberto
Rivero, Michel
Powiązania:
https://bibliotekanauki.pl/articles/2055060.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
bifurcations
natural convection
partially heated cylinder
switching modes solutions
Opis:
This work presents a numerical study on a natural convective flow in a cylindrical container heated from below, cooled from above, and partially heated from the lateral wall. Mass, momentum and energy equations were solved with a developed hybrid Fourier-finite volume code and validated with the commercial software COMSOL Multiphysics for steady-state solutions. The primary solutions correspond to steady-states Cm with azimuthal wavenumbers m. The results show mode competition between different states leading to many flow solutions including steady axisymmetric, steady non-axisymmetric, time-dependent pulsating wave solutions, and other flow states with a variety of spatiotemporal symmetries.
Źródło:
Journal of Theoretical and Applied Mechanics; 2021, 59, 4; 623--636
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Natural convection from four circular cylinders in across arrangement within horizontal annular space
Autorzy:
Laidoudi, Houssem
Powiązania:
https://bibliotekanauki.pl/articles/387589.pdf
Data publikacji:
2020
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
natural convection
multiple cylinders
annular space
heat transfer
numerical simulation
Opis:
Numerical investigation is accomplished to study the roles of governing parameters of natural convection on the fluid motion and heat transfer rate of four heated circular cylinders placed inside a circular enclosure of cold surface. The cylinders are positioned in across arrangement. The representative results are obtained within the ranges of initial conditions as: Prandtl number (Pr = 7.1 to 1000) and Rayleigh number (Ra = 103 to 105). The average Nusselt number of each inner cylinder is computed. The effects of thermal buoyancy strength on the fluid motion and temperature are also illustrated. It was found that the heat transfer rate of cylinders depends significantly on the position inside the enclosure. Moreover, the role of Prandtl number on flow and thermal patterns is negligible. The values of Nusselt number are also given, which can be useful for some engineering applications.
Źródło:
Acta Mechanica et Automatica; 2020, 14, 2; 98-102
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The modified XFEM for solving problems of a phase change with natural convection
Autorzy:
Stąpór, Paweł
Powiązania:
https://bibliotekanauki.pl/articles/139838.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
phase change
natural convection
extended finite element method
level set method
Opis:
This paper presents an extended finite element method applied to solve phase change problems taking into account natural convection in the liquid phase. It is assumed that the transition from one state to another, e.g., during the solidification of pure metals, is discontinuous and that the physical properties of the phases vary across the interface. According to the classical Stefan condition, the location, topology and rate of the interface changes are determined by the jump in the heat flux. The incompressible Navier–Stokes equations with the Boussinesq approximation of the natural convection flow are solved for the liquid phase. The no-slip condition for velocity and the melting/freezing condition for temperature are imposed on the interface using penalty method. The fractional four-step method is employed for analysing conjugate heat transfer and unsteady viscous flow. The phase interface is tracked by the level set method defined on the same finite element mesh. A new combination of extended basis functions is proposed to approximate the discontinuity in the derivative of the temperature, velocity and the pressure fields. The single-mesh approach is demonstrated using three two-dimensional benchmark problems. The results are compared with the numerical and experimental data obtained by other authors.
Źródło:
Archive of Mechanical Engineering; 2019, LXVI, 3; 273-294
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Mechanistic Model of a Passive Autocatalytic Hydrogen Recombiner
Autorzy:
Rożeń, A.
Powiązania:
https://bibliotekanauki.pl/articles/184900.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
hydrogen
catalysis
laminar flow
natural convection
forced convection
wodór
kataliza
przepływ laminarny
konwekcja naturalna
konwekcja wymuszona
Opis:
A passive autocatalytic hydrogen recombiner (PAR) is a self-starting device, without operator action or external power input, installed in nuclear power plants to remove hydrogen from the containment building of a nuclear reactor. A new mechanistic model of PAR has been presented and validated by experimental data and results of Computational Fluid Dynamics (CFD) simulations. The model allows to quickly and accurately predict gas temperature and composition, catalyst temperature and hydrogen recombination rate. It is assumed in the model that an exothermic recombination reaction of hydrogen and oxygen proceeds at the catalyst surface only, while processes of heat and mass transport occur by assisted natural and forced convection in non-isothermal and laminar gas flow conditions in vertical channels between catalyst plates. The model accounts for heat radiation from a hot catalyst surface and has no adjustable parameters. It can be combined with an equation of chimney draft and become a useful engineering tool for selection and optimisation of catalytic recombiner geometry.
Źródło:
Chemical and Process Engineering; 2015, 36, 1; 3-19
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Open-Source CFD analysis of multi-domain unsteady heating with natural convection
Autorzy:
Sosnowski, P.
Pozorski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1943189.pdf
Data publikacji:
2009
Wydawca:
Politechnika Gdańska
Tematy:
CFD
open source software
unsteady heating
natural convection
multi-domain heat transfer
Opis:
The paper presents the capabilities of open-source programs used for numerical simulation of fluid flow and heat transfer phenomena. These tools are applied for unsteady problems with natural convection and, in particular, the heating of an automotive headlight. To perform these studies, a solver was created using an open-source C++ library OpenFOAM. The implementation problems encountered were, inter alia, dealing with multi-domain computation and coupling of sub-domains. The presented simulation results clearly show that open-source software can readily be applied also to engineering problems and can compete with commercial packages.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2009, 13, 4; 403-414
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intensification of free-convection heat transfer in magnetically assisted bioreactor
Autorzy:
Konopacki, Maciej
Kordas, Marian
Rakoczy, Rafał
Powiązania:
https://bibliotekanauki.pl/articles/185473.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
natural convection
rotating magnetic field
magnetically assisted bioreactor
Naturalna konwekcja
wirujące pole magnetyczne
bioreaktor wspomagany magnetycznie
Opis:
The effect of rotating magnetic field on the heat transfer process in a magnetically assisted bioreactor was studied experimentally. Experimental investigations are provided for the explanation of the influence of the rotating magnetic field on natural convection. The heat transfer coefficients and the Nusselt numbers were determined as a function of the product of Grashof and Prandtl dimensionless numbers. Moreover, the comparison of the thermal performance between the tested set-up and a vertical cylinder was carried out. The relative enhancement of heat transfer was characterized by the rate of the relative heat transfer intensification. The study showed that along with the intensity of the magnetic field the heat transfer increased.
Źródło:
Chemical and Process Engineering; 2019, 40, 3; 293--304
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Artificial neural network to predict the natural convection from vertical and inclined arrays of horizontal cylinders
Autorzy:
Amiri, A.
Karami, A.
Yousefi, T.
Zanjani, M.
Powiązania:
https://bibliotekanauki.pl/articles/779019.pdf
Data publikacji:
2012
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
natural convection
Inclined Array
Vertical Array
modeling
artificial neural network
Opis:
The main focus of the present study is to utilize the artifi cial neural network (ANN) in predicting the natural convection from horizontal isothermal cylinders arranged in vertical and inclined arrays. The effects of the vertical separation spacing to the cylinder diameter ratio (Py/d), horizontal separation spacing to the cylinder diameter ratio (Px/d) and Rayleigh number (Ra) variation on the average heat transfer from the arrays are considered via this prediction. The training data for optimizing the ANN structure is based on available experimental data. The Levenberg-Marquardt back propagation algorithm is used for ANN training. The proposed ANN is developed using MATLAB functions. For the best ANN structure obtained in this investigation, the mean relative errors of 0.027% and 0.482% were reached for the training and test data, respectively. The results show that the predicted values are very close to the experimental ones.
Źródło:
Polish Journal of Chemical Technology; 2012, 14, 4; 46-52
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie konwekcji swobodnej z powierzchni pionowego walca w środowisku hiperbarycznym
Experimental investigation of natural convection from vertical cylinder in the hyperbaric environment
Autorzy:
Majchrzycka, A.
Powiązania:
https://bibliotekanauki.pl/articles/366405.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Medycyny i Techniki Hiperbarycznej
Tematy:
konwekcja swobodna
pionowy walec
hel
natural convection
vertical cylinder
helium
Opis:
W pracy przedstawiono badania, dotyczące konwekcji swobodnej z powierzchni pionowego walca odwzorowującego sylwetkę nurka o zmiennym wydatku energetycznym. Badania wykonano w helu o ciśnieniu p = 0,5-5MPa, a wyniki przedstawiono postaci równania kryterialnego Nu = f(Ra) oraz korelacji, która umożliwia obliczenie współczynnika przejmowania ciepła w funkcji ciśnienia gazu i symulowanego wydatku energetycznego nurka.
The paper reports experimental investigation of natural convection from vertical cylinder that simulates the diver’s body of the different activity level. Experiments were carried out in the hyperbaric helium at absolute pressure range of p=0,5-5 MPa. The results are given as the correlation Nu = f(Ra) and correlation between convective heat transfer coefficient from the outer surface of vertical cylinder, pressure and simulated activity level.
Źródło:
Polish Hyperbaric Research; 2010, 1(30); 13-24
1734-7009
2084-0535
Pojawia się w:
Polish Hyperbaric Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the occurrence of natural convection in a bed of bars in vertical temperature gradient conditions
Autorzy:
Wyczółkowski, R.
Musiał, D.
Powiązania:
https://bibliotekanauki.pl/articles/239971.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
natural convection
bed of bars
porous material
konwekcja naturalna
złoża prętów
materiały porowate
Opis:
The reason for undertaking this study was to determine the possible involvement of natural convection in the global heat transfer, that occurs in the heated steel rods bed. This problem is related to the setting of the effective thermal conductivity of the bars bed. This value is one of the boundary conditions for heating modeling of steel rods bundles during heat treatment. The aim of this study was to determine for which geometry of the bed bars, there will be no free convection. To analyze the problem the Rayleigh criterion was used. It was assumed that for the value of the number Ra < 1700 convection in the bed bars does not occur. For analysis, the results of measurements of the temperature distribution in the unidirectionally heated beds of bars were used. It has been shown, that for obtained, during the test, differences of temperature between the surfaces of adjacent rods, convection can occur only when the diameter of the rod exceeds 18 mm.
Źródło:
Archives of Thermodynamics; 2013, 34, 1; 71-83
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of radial fins on natural convection between horizontal circular and square cylinders
Autorzy:
Jafari, I.
Mahdavy-Moghadam, H.
Taeibi-Rahni, M.
Dayyan, M.
Seyyedi, S. M.
Powiązania:
https://bibliotekanauki.pl/articles/279844.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
radial fins
natural convection
lattice Boltzmann method
horizontal annulus
Opis:
In this paper, the effects of the number and arrangement of radial fins on laminar natural co- nvection between horizontal circular and square cylinders has been investigated numerically with the lattice Boltzmann method. The Rayleigh number is varied from Ra = 10³ − 10⁶), the number of fins (N = 2 − 8) and the Prandtl number (Pr = 0.7). The local Nusselt number profiles over the outer and inner cylinders and the average Nusselt number over the top, bottom and side walls of the outer cold square cylinder are obtained. The temperature and streamline contours are also depicted to investigate the heat and fluid flow behavior inside the computational domain.
Źródło:
Journal of Theoretical and Applied Mechanics; 2014, 52, 3; 827-837
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The natural convection inside a 3D triangular cross section cavity filled with nanofluid and included cylinder with different arrangements
Autorzy:
Ghoben, Zainab Kareem
Hussein, Ahmed Kadhim
Powiązania:
https://bibliotekanauki.pl/articles/2096184.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
natural convection
triangular cavity
inner cylinder
nanofluid
3D
konwekcja naturalna
Opis:
In this paper the laminar unsteady natural convection heat transfer of (Al2O3-water) nanofluid inside 3D triangular cross section cavity was investigated. The cavity was heated differentially, the vertical walls were kept at different constant temperatures. The left hot and the right cold. The effect of the solid volume fraction was examined for two values and compared with the pure water results. The (Ra) range studied was (103≤Ra≤106). Inserting cylindrical body inside the cavity also investigated in three cases. One concentric cylinder has radius (15%) of the cavity side length. The other cases were of two cylinders having radius (7.5%) of the cavity side length, aligned vertically or nonaligned. The results show that the higher solid volume fraction gives the maximum enhancement of the average (Nu) and this enhancement increases with (Ra) increase. For the cases with inner cylinders, the average (Nu) enhanced for the case of double cylinders over single cylinder. On other hand, the nonaligned position of the cylinders giving more enhancement than other position. As like as, the location of maximum horizontal or vertical velocities were varied with the cylinders position while (Ra) has no effect.
Źródło:
Diagnostyka; 2022, 23, 2; no. art. 2022205
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Natural convection heat transfer in heated vertical tubes with internal rings
Autorzy:
Nayak, R. C.
Roul, M. K.
Sarangi, S. K.
Powiązania:
https://bibliotekanauki.pl/articles/240303.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat flux
heat transfer
natural convection
ring spacing
ring thickness
strumień cieplny
wymiana ciepła
konwekcja naturalna
pierścień
Opis:
Experimental investigation of natural convection heat transfer in heated vertical tubes dissipating heat from the internal surface is presented. The test section is electrically heated and constant wall heat flux is maintained both circumferentially and axially. Four different test sections are taken having 45 mm internal diameter and 3.8 mm thickness. The length of the test sections are 450 mm, 550 mm, 700 mm and 850 mm. Ratios of length to diameter of the test sections are taken as 10, 12.22, 15.56, and 18.89. Wall heat fluxes are maintained at 250–3341 W/m2 . Experiments are also conducted on channels with internal rings of rectangular section placed at various distances. Thickness of the rings are taken as 4 mm, 6 mm, and 8 mm. The step size of the rings varies from 75 mm to 283.3 mm. The nondimensional ring spacing, expressed as the ratios of step size to diameter, are taken from 1.67 to 6.29 and the non-dimensional ring thickness, expressed as the ratios of ring thickness to diameter are taken from 0.089 to 0.178. The ratios of ring spacing to its thickness are taken as 9.375 to 70.82. The effects of various parameters such as length to diameter ratio, wall heat flux, ring thickness and ring spacing on local steady-state heat transfer behavior are observed. From the experimental data a correlation is developed for average Nusselt number and modified Rayleigh number. Another correlation is also developed for modified Rayleigh number and modified Reynolds number. These correlations can predict the data accurately within ±10% error.
Źródło:
Archives of Thermodynamics; 2018, 39, 4; 85--111
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
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
Wyświetlanie 1-15 z 41

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