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Wyszukujesz frazę "convection" wg kryterium: Wszystkie pola


Tytuł:
Mixed convection heat transfer in trapezoidal lid-driven cavity with uniformly heated inner circular cylinder
Autorzy:
Hussein, Asmaa Ali
Powiązania:
https://bibliotekanauki.pl/articles/27312211.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
cavity
heat transfer
mixed convection
lid-driven
Opis:
The present work comprises a numerical analysis using the Ansys program to solve the problem of combined free-forced convection around a circular cylinder located in a horizontal lid-driven trapezoidal enclosure. The enclosure is filled with water. The upper moving wall and lower fixed wall are cold at a constant temperature, whereas the inclined walls are adiabatically insulated. The uniformly heated cylinder is located at different positions in the cavity. The study covers three values of Richardson number (0.01, 1, and 10). The results show that the streamlines and isotherms in the enclosure, the Nusselt number and friction factor in the moving wall, hot wall and bottom wall are strongly dependent on the position of the inner hot cylinder. The results are validated with previous work, and the comparison gives good agreement.
Źródło:
Archives of Thermodynamics; 2023, 44, 3; 99--118
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
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:
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:
Boundary effects on electrothermal convection in a dielectric fluid layer
Autorzy:
Ravisha, M.
Raghunatha, K. R.
Mamatha, A. L.
Shivakumara, I. S.
Powiązania:
https://bibliotekanauki.pl/articles/240648.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
boundary effect
dielectric fluid
AC electric field
thermal convection
konwekcja termiczna
płyn dielektryczny
warunki brzegowe
Opis:
The instability characteristics of a dielectric fluid layer heated from below under the influence of a uniform vertical alternating current (AC) electric field is analyzed for different types of electric potential (constant electric potential/ electric current), velocity (rigid/free) and temperature boundary conditions (constant temperature/heat flux or a mixed condition at the upper boundary). The resulting eigenvalue problem is solved numerically using the shooting method for various boundary conditions and the solution is also found in a simple closed form when the perturbation heat flux is zero at the boundaries. The possibility of a more precise control of electrothermal convection (ETC) through various boundary conditions is emphasized. The effect of increasing AC electric Rayleigh number is to hasten while that of Biot number is to delay the onset of ETC. The system is more stable for rigid-rigid boundaries when compared to rigid-free and least stable for free-free boundaries. The change of electric potential boundary condition at the upper boundary from constant electric potential to constant electric current is found to instill more stability on the system.
Źródło:
Archives of Thermodynamics; 2019, 40, 1; 3-19
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mixed convection heat transfer of a nanofluid in a square ventilated cavity separated horizontally by a porous layer and discrete heat source
Autorzy:
Messaoud, Hamdi
Adel, Sahi
Ouerdia, Ourrad
Powiązania:
https://bibliotekanauki.pl/articles/27312228.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
mixed convection
vented cavity
porous layer
finite volume method
Opis:
Laminar mixed convection heat transfer in a vented square cavity separated by a porous layer filled with different nanofluids (Fe3O4, Cu, Ag and Al2O3) has been investigated numerically. The governing equations of mixed convection flow for a Newtonian nanofluid are assumed to be two-dimensional, steady and laminar. These equations are solved numerically by using the finite volume technique. The effects of significant parameters such as the Reynolds number (10 ≤ Re ≤ 1000), Grashof number (103 ≤ Gr ≤ 106 ), nanoparticle volume fraction (0.1 ≤ φ ≤ 0.6), porous layer thickness (0 ≤ γ ≤ 1) and porous layer position (0.1 ≤ δ ≤ 0.9) are studied. Numerical simulation details are visualized in terms of streamline, isotherm contours, and average Nusselt number along the heated source. It has been shown that variations in Reynolds and Darcy numbers have an impact on the flow pattern and heat transfer within a cavity. For higher Reynolds (Re > 100), Grashof (Gr > 105 ) numbers and nanoparticles volume fractions the heat transfer rate is enhanced and it is optimal at lower values of Darcy number (Da = 10−5 ). In addition, it is noticed that the porous layer thickness and location have a significant effect on the control of the heat transfer rate inside the cavity. Furthermore, it is worth noticing that Ag nanoparticles presented the largest heated transfer rate compared to other nanoparticles.
Źródło:
Archives of Thermodynamics; 2023, 44, 2; 87--114
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
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:
Unsteady natural convection in micropolar nanofluids
Autorzy:
Rup, K.
Nering, K.
Powiązania:
https://bibliotekanauki.pl/articles/240090.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
micropolar fluid
nanofluid
heat transfer enhancement
płyn mikropolarny
nanopłyn
intensyfikacja wymiany ciepła
Opis:
This paper presents the analysis of momentum, angular momentum and heat transfer during unsteady natural convection in micropolar nanofluids. Selected nanofluids treated as single phase fluids contain small particles with diameter size 10-38.4 nm. In particular three water-based nanofluids were analyzed. Volume fraction of these solutions was 6%. The first of the analyzed nanofluids contained TiO2 nanoparticles, the second one contained Al2O3 nanoparticles, and the third one the Cu nanoparticles.
Źródło:
Archives of Thermodynamics; 2014, 35, 3; 155-170
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
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 effect of reduced heat transfer in a micropolar fluid in natural convection
Autorzy:
Rup, K.
Dróżdż, A.
Powiązania:
https://bibliotekanauki.pl/articles/240722.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
micropolar fluid
microrotation
boundary layer theory
Local Nusselt number
teoria warstwy przyściennej
Liczba Nusselta
Opis:
This paper presents the numerical solution to the unsteady natural convection problem in micropolar fluid in the vicinity of a vertical plate, heat flux of which rises suddenly at a given moment. In order to solve this problem the method of finite differences was applied. The numerical results have been presented for a range of values of the dimensionless material properties and fluid Prandtl number. The analysis of the results shows that the intensity of the heat transfer in micropolar fluid is lower compared to the Newtonian fluid.
Źródło:
Archives of Thermodynamics; 2013, 34, 3; 45-59
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of forced convection of nanofluid around a circular cylinder
Autorzy:
Korib, Kamel
Ihaddadene, Nabila
Bouakkaz, Rafik
Khelili, Yacine
Powiązania:
https://bibliotekanauki.pl/articles/240282.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
copper nanoparticles
heat transfer
circular cylinder
steady regime
walec kołowy
wymiana ciepła
nanocząstki miedzi
Opis:
In this study a steady flow-field and heat transfer through a copper-water nanofluid around a circular cylinder, under the influence of both the standard thermal boundary conditions, i.e., uniform heat flux and constant wall temperature) was investigated numerically by using a finitevolume method for Reynolds numbers from the range 10–40. Furthermore, the range of nanoparticle volume fractions considered is 0–5%. The variation of the local and the average Nusselt numbers with Reynolds number, and volume fractions are presented for the range of conditions. The average Nusselt number is found to increase with increasing the nanoparticle volume fractions.
Źródło:
Archives of Thermodynamics; 2019, 40, 2; 3-16
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of hall currents on thermal instability of dusty couple stress fluid
Autorzy:
Aggarwal, A. K.
Verma, A.
Powiązania:
https://bibliotekanauki.pl/articles/240229.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
couple-stress fluid
dust particles
hall currents
stationary convection
oscillatory modes
magnetic field
ziarna pyłu
konwekcja
pole magnetyczne
Opis:
In this paper, effect of Hall currents on the thermal instability of couple-stress fluid permeated with dust particles has been considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For the case of stationary convection, dust particles and Hall currents are found to have destabilizing effect while couple stresses have stabilizing effect on the system. Magnetic field induced by Hall currents has stabilizing/destabilizing effect under certain conditions. It is found that due to the presence of Hall currents (hence magnetic field), oscillatory modes are produced which were non-existent in their absence.
Źródło:
Archives of Thermodynamics; 2016, 37, 3; 3-18
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical study of an air plane solar collector with the baffle in zigzag form
Autorzy:
Guendouz, N.
Bibi-Triki, N.
Didi, F.
Zidani, C.
Powiązania:
https://bibliotekanauki.pl/articles/240592.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
turbulent flow
forced convection
rectangular pipe
baffle
heat transfer
przepływ turbulentny
konwekcja wymuszona
przegroda
wymiana ciepła
Opis:
The production of thermal energy from solar energy by flat collectors finds nowadays many applications due to their innumerable economic and environmental interests. Currently, conservation of energy resources has become a global priority. On the other hand, given the dizzying demand for energy, has led specialists to find new techniques, such as renewable energies (solar, wind and geothermal). The present work is a contribution, by numerical simulation, to the study of heat transfer in flat solar collectors. On the basis of some experimental data, several simulation calculations have been carried out in order to determine the influencing parameters allowing better performance of the sensors and ensuring a good homogeneity of the temperature distributions. Based on the observation that, due to the low thermophysical properties of the air used as heat transfer fluid, solar air collectors rather give poor yields. It has been found very useful to have ‘baffling’ obstacles of various shapes and forms in the solar collector duct. This increases the thermal transfer of a coolant, which clearly improves the thermal efficiency of the solar air collector. This article consists mainly of studying the effects on heat transfer of turbulent forced convection by baffles of zigzag shapes, placed in a rectangular channel, using the finite volume method. The pressure-velocity coupling has been processed by the SIMPLEC algorithm. The results are presented in terms of the average Nusselt number and temperature field for different positions.
Źródło:
Archives of Thermodynamics; 2018, 39, 4; 141--156
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unconfined laminar nanofluid flow and heat transfer around a rotating circular cylinder in the steady regime
Autorzy:
Bouakkaz, R.
Salhi, F.
Khelili, Y.
Quazzazi, M.
Talbi, K.
Powiązania:
https://bibliotekanauki.pl/articles/240108.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nanofluid
rotating circular cylinder
forced convection
steady regime
obracanie
cylinder okrągły
konwekcja wymuszona
Opis:
In this work, steady flow-field and heat transfer through a copper-water nanofluid around a rotating circular cylinder with a constant nondimensional rotation rate α varying from 0 to 5 was investigated for Reynolds numbers of 5–40. Furthermore, the range of nanoparticle volume fractions considered is 0–5%. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are carried out by using a finite-volume method based commercial computational fluid dynamics solver. The variation of the local and the average Nusselt numbers with Reynolds number, volume fractions, and rotation rate are presented for the range of conditions. The average Nusselt number is found to decrease with increasing value of the rotation rate for the fixed value of the Reynolds number and volume fraction of nanoparticles. In addition, rotation can be used as a drag reduction technique.
Źródło:
Archives of Thermodynamics; 2017, 38, 2; 3-20
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
Autorzy:
Muszyński, T.
Kozieł, S. M.
Powiązania:
https://bibliotekanauki.pl/articles/240658.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchangers
heat transfer intensification
CFD
convection
air source heat pump
wymienniki ciepła
intensyfikacja wymiany ciepła
konwekcja
powietrzne pompy ciepła
Opis:
Two-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evaporator. The transferred heat and the pressure drop predicted by simulation have been compared with the corresponding experimental data taken from the literature. Two dimensional analyses of the louvered fins with varying geometry have been conducted. Simulations have been performed for different geometries with varying louver pitch, louver angle and different louver blade number. Constant inlet air temperature and varying velocity ranging from 2 to 8 m/s was assumed in the numerical experiments. The air-side performance is evaluated by calculating the temperature and the pressure drop ratio. Efficiency curves are obtained that can be used to select optimum louver geometry for the selected inlet parameters. A total of 363 different cases of various fin geometry for 7 different air velocities were investigated. The maximum heat transfer improvement interpreted in terms of the maximum efficiency has been obtained for the louver angle of 16° and the louver pitch of 1.35 mm. The presented results indicate that varying louver geometry might be a convenient way of enhancing performance of heat exchangers.
Źródło:
Archives of Thermodynamics; 2016, 37, 3; 45-62
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of variable viscosity on free flow of non-Newtonian power-law fluids along a vertical surface with thermal stratification
Autorzy:
Moorthy, M.
Senthilvadivu, K.
Powiązania:
https://bibliotekanauki.pl/articles/240778.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ośrodek porowaty
stratyfikacja termiczna
swobodna konwekcja
zmienna lepkość
free convection
non-Newtonian
porous medium
thermal stratification
variable viscosity
Opis:
The aim of this paper is to investigate the effect of thermal stratification together with variable viscosity on free convection flow of non-Newtonian fluids along a nonisothermal semi infinite vertical plate embedded in a saturated porous medium. The governing equations of continuity, momentum and energy are transformed into nonlinear ordinary differential equations using similarity transformations and then solved by using the Runge-Kutta-Gill method along with shooting technique. Governing parameters for the problem under study are the variable viscosity, thermal stratification parameter, non-Newtonian parameter and the power-law index parameter.The velocity and temperature distributions are presented and discussed. The Nusselt number is also derived and discussed numerically.
Źródło:
Archives of Thermodynamics; 2012, 33, 4; 109-121
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł

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