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Wyświetlanie 1-10 z 226
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:
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 Analysis of Convective Heat Transfer for Selected Geometric System
Autorzy:
Orłowska, Magdalena
Powiązania:
https://bibliotekanauki.pl/articles/2174927.pdf
Data publikacji:
2022
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
convection
intensification
protect
environment
Opis:
The contemporary problems and issues of environmental protection refer to a large extent to problems related – generally speaking – to energy. Currently, the production processes mainly concern the combustion of energy fuels, transport – over long distances, and their use for utility purposes, e.g. engine drive or heating. These processes significantly negatively impact the environment and are magnified by their enormous intensity and size. While energy production and transport processes have been studied for many years, and their results are widely published, the issues related to the application and operation of heating devices are little known and require much observation and research. The operating indicators of heating devices are generally characterized by low values (natural convection), and their artificial increase (intensity) cannot be used due to the acoustic effects and additional (significant) investment costs. The article presents some research results on the intensification of heat flow – i.e. the thermal efficiency of flat heaters placed in a room with a specific temperature. Physical phenomena were investigated numerically by shaping the heat exchange space. The tested systems concerned a room with a free-standing heater, a heater with a vertical panel mounted in parallel, and a system with a curved bottom plate forming the so-called de Laval nozzle. Interesting results of air velocity and temperature fields and values of the heat transfer coefficient along the height of the heater were obtained. Based on the presented research, it can be concluded that the creation of convection surfaces around the heater is advisable because it affects the intensity of heat exchange, which can be increased without energy-intensive energy expenditure, i.e. in a non-mechanical way. Undoubtedly contributes positively to investment and operating costs, which is essential in environmental protection issues.
Źródło:
Rocznik Ochrona Środowiska; 2022, 24; 163--171
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rotating Rayleigh-Benard convection
Autorzy:
Majchrowski, W.
Tuliszka-Sznitko, E.
Powiązania:
https://bibliotekanauki.pl/articles/1943236.pdf
Data publikacji:
2008
Wydawca:
Politechnika Gdańska
Tematy:
DNS
Rayleigh-Benard convection
Opis:
In the this paper our results on the natural convection in an enclosed rotating cavity are presented. We have focused our attention on the influence of the Rayleigh and Taylor numbers on the flow structure. DNS computations have been performed for the geometry of aspect ratio L=9 and curvature parameter Rm=1.5.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2008, 12, 3-4; 267-272
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Behaviour of a non-newtonian fluid in a helical tube under the influence of thermal buoyancy
Autorzy:
Ramla, Mohamed
Laidoudi, Houssem
Bouzit, Mohamed
Powiązania:
https://bibliotekanauki.pl/articles/2105993.pdf
Data publikacji:
2022
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
helical heat exchanger
mixed convection
forced convection
power-law fluids
Nusselt number
Opis:
This work is an evaluative study of heat transfer in the helical-type heat exchanger. The fluid used is non-Newtonian in nature and is defined by Oswald’s model. The work was performed numerically by solving each of the Navier–Stokes equations and the energy equation using the package ANSYS-CFX. Following are the aspects that have been dealt with in this paper: the effects of thermal buoyan-cy, fluid nature and the tube shape on the heat transfer, and the fluid comportment. The interpretation of the obtained results was done by analyzing the isotherms and the streamlines. The mean values of the Nusselt number were also obtained in terms of the studied parame-ters. The results of this research enabled us to arrive at the following conclusion: the intensity of thermal buoyancy and the nature of the fluid affect the heat transfer distribution but keep the overall rate of heat transfer the same.
Źródło:
Acta Mechanica et Automatica; 2022, 16, 2; 111--118
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Global stability for thermal convection in a couple-stress fluid with temperature and pressure dependent viscosity
Autorzy:
Choudhary, S. S.
Bharti, P. K.
Powiązania:
https://bibliotekanauki.pl/articles/178230.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
konwekcja
konwekcja cieplna
stabilność
płyn nieniutonowski
convection
thermal convection
stability
non-Newtonian fluid
Opis:
We show that the global nonlinear stability threshold for convection in a couple-stress fluid with temperature and pressure dependent viscosity is exactly the same as the linear instability boundary. This optimal result is important because it shows that linearized instability theory has captured completely the physics of the onset of convection. It has also been found that the couplestress fluid is more stable than the ordinary viscous fluid and then the effect of couple-stress parameter (F) and variable dependent viscosity (Γ) on the onset of convection is also analyzed.
Źródło:
Studia Geotechnica et Mechanica; 2013, 35, 3; 85-102
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sensitivities of the Tiedtke and Kain-Fritsch Convection Schemes for RegCM4.5 over West Africa
Autorzy:
Adeniyi, Mojisola Oluwayemisi
Powiązania:
https://bibliotekanauki.pl/articles/108457.pdf
Data publikacji:
2019
Wydawca:
Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy
Tematy:
convective precipitation
West African monsoon
Kain-Fritsch convection scheme
Tiedtke convection scheme
African easterly jet
Opis:
Realistic simulation of weather and climate parameters over West Africa is daunting, so the performance of the Tiedtke and Kain-Fritsch convection schemes within version 4.5 of the Regional Climate Model (RegCM4.5) of the International Centre for Theoretical Physics, Trieste is evaluated over West Africa for improved simulation. The two schemes are compared to two traditional mixture schemes (Grell on land and Emanuel on Ocean), outperforming the mixture schemes with reduced magnitude and spatial coverage of dry bias. Both schemes simulate precipitation over West Africa with a low dry bias, however, the Kain-Fritsch convection scheme simulates more realistic precipitation in the West African convective environment. This is associated with the inclusion of a variable cloud radius and the convective available potential energy closure for the Kain-Fritsch in contrast to a fixed cloud radius and moisture convergence of the of the Tiedtke scheme. The simulated outgoing longwave radiation and omega lend support to the spatial variations and amount of simulated precipitation in the different areas by the schemes. The spatial variation of simulated temperature over the target region shows lower bias than precipitation by all the convection schemes. Soil moisture is more accurately simulated (correlation coefficient ~1) in the savannah (8-10°N) and Sahel (22-28°N) environments by all the convection schemes. Tiedtke performs the most accurate simulations of the pattern and profile of zonal wind which controls climate circulation, with slightly weaker simulations of the Africa easterly jet with core magnitude less than 10 m·s-1. The accuracy of the KF and Tiedtke in RegCM4.5 in simulating the climate of West Africa is documented for the first time for application in future studies over the region.
Źródło:
Meteorology Hydrology and Water Management. Research and Operational Applications; 2019, 7, 2; 27-37
2299-3835
2353-5652
Pojawia się w:
Meteorology Hydrology and Water Management. Research and Operational Applications
Dostawca treści:
Biblioteka Nauki
Artykuł
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:
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:
Rayleigh-Bénard convection in an elastico-viscous Walters’ (model B’) nanofluid layer
Autorzy:
Rana, G. C.
Chand, R.
Powiązania:
https://bibliotekanauki.pl/articles/202036.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nanofluid
oscillatory convection
Rayleigh-Benard convection
viscoelasticity
Walters' (model B') fluid
oscylacyjna konwekcyjna
komórki Bénarda
lepkosprężystość
Opis:
In this study, the onset of convection in an elastico-viscous Walters’ (model B’) nanofluid horizontal layer heated from below is considered. The Walters’ (model B’) fluid model is employed to describe the rheological behavior of the nanofluid. By applying the linear stability theory and a normal mode analysis method, the dispersion relation has been derived. For the case of stationary convection, it is observed that the Walters’ (model B’) elastico-viscous nanofluid behaves like an ordinary Newtonian nanofluid. The effects of the various physical parameters of the system, namely, the concentration Rayleigh number, Prandtl number, capacity ratio, Lewis number and kinematics visco-elasticity coefficient on the stability of the system has been numerically investigated. In addition, sufficient conditions for the non-existence of oscillatory convection are also derived.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2015, 63, 1; 235-244
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 226

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