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Wyświetlanie 1-15 z 41
Tytuł:
Optimization of heat transfer oriented surfaces by thermovision and using CFD method
Autorzy:
Kapjor, A.
Smatanová, H.
Hužvár, J.
Greššak, T.
Jandačka, J.
Powiązania:
https://bibliotekanauki.pl/articles/402248.pdf
Data publikacji:
2013
Wydawca:
Politechnika Świętokrzyska w Kielcach. Wydawnictwo PŚw
Tematy:
heat transfer
natural convection
CFD method
Opis:
The paper presents applications of infrared measurements. It discusses the use of thermovision and CFD method in the analysis of heat transfer in experimental measurement with natural convection.
Źródło:
Structure and Environment; 2013, 5, 4; 41-44
2081-1500
Pojawia się w:
Structure and Environment
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy production due to conjugate natural convection in a nanofluid-filled enclosure with a stepped wall
Autorzy:
Bouchoucha, Abd el
Oztop, Hakan F.
Bessaih, Rachid
Abu-Hamdeh, Nidal
Powiązania:
https://bibliotekanauki.pl/articles/38894787.pdf
Data publikacji:
2023
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
entropy generation
natural convection
nanofluids
cavity
wall
Opis:
The main aim of this paper is to improve the heat transfer in a square cavity with a body at the left wall filled with a Al2O3/water nanofluid for different geometries. Numerous simulation experiments are conducted. A relative temperature is maintained at the vertical and top horizontal walls while the bottom wall is warm. The finite volume approach is considered to resolve the equations governing the thermal transfer flow in the physical domain based on the SIMPLER algorithm. In this study, different values of the following parameters are considered: Rayleigh number (104 ≤ Ra ≤ 105) and solid volume fraction (0 ≤ φ ≤ 0.1) of nanoparticles (NPs). Parameters, such as the Rayleigh (Ra) and Bejan (Be) numbers, thermal conductivity, body’s dimensions, and NPs volume fraction, which directly affect the entropy generation and heat transfer rate, are studied in a particular way. The obtained results show that entropy generation goes ahead with the Ra increase and inverse to the solid volume fraction increase. One can notice that the heat transfer has a proportional relation with φ and Ra.
Źródło:
Engineering Transactions; 2023, 71, 2; 161-183
0867-888X
Pojawia się w:
Engineering Transactions
Dostawca treści:
Biblioteka Nauki
Artykuł
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:
Numerical modelling and analysis of cooling system of electrical transformer dipped into polymerised resin
Autorzy:
Smołka, J.
Nowak, A. J.
Wrobel, L. C.
Powiązania:
https://bibliotekanauki.pl/articles/1955729.pdf
Data publikacji:
2003
Wydawca:
Politechnika Gdańska
Tematy:
dry electrical transformer
heat transfer
natural convection
coupled analysis
Opis:
This paper discusses a numerical model of the heat dissipation processes in an electrical transformer dipped into polymerised resin. The transformer is cooled by both natural convection (via the ambient air) and forced convection (via the water cooling system attached to one of the transformer casing walls). Two cases have been compared, i.e. the cooler connected to the bottom or the top wall of the transformer container, respectively. In order to improve the modelling of the natural convection problem, an independent geometrical model of the surrounding air was created and considered separately. The continuity of temperature and heat flux along the interface between the transformer and air was enforced by an iterative procedure. This procedure allowed one to calculate and then prescribe local heat fluxes to the external walls of the transformer. The numerical results obtained in this project have yielded information on the efficiency of the analysed cooling system.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2003, 7, 3; 439-448
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mathematical modeling of large floating roof reservoir temperature arena
Autorzy:
Liu, Y.
Fan, J.
Cheng, Q.
Powiązania:
https://bibliotekanauki.pl/articles/778000.pdf
Data publikacji:
2018
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
floating roof tank
temperature field
natural convection
numerical simulation
Opis:
The current study is a simplification of related components of large floating roof tank and modeling for three dimensional temperature field of large floating roof tank. The heat transfer involves its transfer between the hot fluid in the oil tank, between the hot fluid and the tank wall and between the tank wall and the external environment. The mathematical model of heat transfer and flow of oil in the tank simulates the temperature field of oil in tank. Oil temperature field of large floating roof tank is obtained by numerical simulation, map the curve of central temperature dynamics with time and analyze axial and radial temperature of storage tank. It determines the distribution of low temperature storage tank location based on the thickness of the reservoir temperature. Finally, it compared the calculated results and the field test data; eventually validated the calculated results based on the experimental results.
Źródło:
Polish Journal of Chemical Technology; 2018, 20, 1; 67-74
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
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:
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:
Natural convection flow in semi-trapezoidal porous enclosure filled with alumina-water nanofluid using Tiwari and Das’ nanofluid model
Autorzy:
Vedavathi, Nallapati
Venkatadri, Kothuru
Fazuruddin, Syed
Raju, G. Sankara Sekhar
Powiązania:
https://bibliotekanauki.pl/articles/38889212.pdf
Data publikacji:
2022
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
natural convection
laminar flow
porous medium
nanofluid
semi-trapezoidal enclosure
Opis:
Nowadays, optimal parameters are necessary for heat transfer enhancement in different practical applications. A numerical simulation of natural convection in a semi-trapezoidal enclosure embedded with porous medium is presented. Stream function and temperature using the Darcy–Boussinesq approximation and Tiwari and Das’ nanofluid model with new more realistic empirical correlations for the physical properties of the nanofluids are formulated. The developed partial differential equations are employed with the help of the stream function approach. The in-house developed computational MATLAB code is validated with the previously published work. The impact of a wide range of governing parameters on fluid flow patterns and temperature gradient variations is presented. The thermal Rayleigh number (Ra) can be a control key parameter for heat and convective flow. Thermal dispersion effects are also examined in this study. An increase in the Rayleigh number leads to an increase in heat transfer, where one can find a reduction of convective heat transfer with φ.
Źródło:
Engineering Transactions; 2022, 70, 4; 303-318
0867-888X
Pojawia się w:
Engineering Transactions
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:
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:
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:
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:
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:
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
Wyświetlanie 1-15 z 41

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