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Wyświetlanie 1-15 z 28
Tytuł:
Analysis of transient natural convective flow of a nanofluid in a vertical tube
Autorzy:
Jha, Basant K.
Chitumu, Ali J.
Oni, Michael O.
Powiązania:
https://bibliotekanauki.pl/articles/1839829.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
nanociecze
naturalna konwekcja
wymiana ciepła
nanofluid
transient
natural convection
heat transfer
vertical tube
Opis:
An analysis into the transient natural convective flow of a nanofluid in a vertical tube is made. The governing equations of momentum, heat transfer and nanoparticle volume fraction are deduced, and the influence of the thermophoresis parameter and Brownian motion is incorporated. By direct integration and variation of the parameter, analytical solutions are obtained for flow formation and heat/mass transfer at steady-state. On the other hand, due to the complexity of same problem at transient state, a numerical solution is used to solve the discretized equations of motion using the implicit finite difference technique. The influence of the thermophoresis parameter and Brownian motion is noted and well discussed. For accuracy check, a numerical comparison is made between the steady state and transient state solution at large time; this comparison gives an excellent agreement. The role of various principal parameters on velocity profile, temperature, concentration of nanoparticles, Sherwood and Nusselt numbers are presented graphically and well discussed. It is noted that the buoyancy ratio decreases the fluid velocity significantly.
Źródło:
International Journal of Applied Mechanics and Engineering; 2021, 26, 2; 31-46
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
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:
Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner
Autorzy:
Rożeń, A.
Powiązania:
https://bibliotekanauki.pl/articles/146233.pdf
Data publikacji:
2018
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
catalytic recombination
computational fluid dynamics
hydrogen safety
natural convection
rekombinacja katalityczna
obliczeniowa dynamika płynów
naturalna konwekcja
Opis:
Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear reactor (LWR). Inside a passive autocatalytic recombiner (PAR), hydrogen and oxygen molecules are adsorbed at catalyst active spots and they recombine to yield water. Heat released in this exothermic reaction creates natural convection of gas in the spaces between the elements supporting a catalyst. Hot and humid gas fl ows upwards into the PAR chimney, while fresh, hydrogen-rich gas enters the PAR from below. Catalytic recombination should start spontaneously at room temperature and low hydrogen concentration. Computational fl uid dynamics (CFD) has been used to study the dynamic behaviour of a plate-type Areva FR-380 recombiner in a quiescent environment for several test scenarios, including different rates of increase in hydrogen concentration and temporary catalyst deactivation. A method for the determination of pressure boundary conditions at the PAR exits was proposed and implemented into a CFD code. In this way, transient operation of PAR could be simulated without the need to model gas circulation outside the device. It was found that fi rst a slow downward fl ow of gas is developed, which may persist until the temperature of the catalyst foils rises. As soon as the gas inside the PAR absorbs enough heat to become lighter than the gas outside the PAR, it starts to fl ow upwards. Criteria for determining the start-up time of PAR were proposed. Model predictions were also compared with experimental data obtained in tests conducted at the THAI facility.
Źródło:
Nukleonika; 2018, 63, 2; 27-41
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal analysis of a fully wet porous radial fin with natural convection and radiation using the spectral collocation method
Autorzy:
Khani, F.
Darvishi, M. T.
Gorla, R. S. R.
Gireesha, B. J.
Powiązania:
https://bibliotekanauki.pl/articles/264453.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
porowatość
naturalna konwekcja
promieniowanie
analiza termiczna
wet porous radial fin
natural convection
radiation
thermal analysis
spectral collocation method
Opis:
Heat transfer with natural convection and radiation effect on a fully wet porous radial fin is considered. The radial velocity of the buoyancy driven flow at any radial location is obtained by applying Darcy’s law. The obtained non-dimensionalized ordinary differential equation involving three highly nonlinear terms is solved numerically with the spectral collocation method. In this approach, the dimensionless temperature is approximated by Chebyshev polynomials and discretized by Chebyshev-Gausse-Lobatto collocation points. A particular algorithm is used to reduce the nonlinearity of the conservation of energy equation. The present analysis characterizes the effect of ambient temperature in different ways and it provides a better picture regarding the effect of ambient temperature on the thermal performance of the fin. The profiles for temperature distributions and dimensionless base heat flow are obtained for different parameters which influence the heat transfer rate.
Źródło:
International Journal of Applied Mechanics and Engineering; 2016, 21, 2; 377-392
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie procesu suszenia konwekcyjnego pietruszki korzeniowej
Testing the convective-drying process of parsley root
Autorzy:
Skorupska, E.
Powiązania:
https://bibliotekanauki.pl/articles/291036.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Inżynierii Rolniczej
Tematy:
suszenie
konwekcja naturalna
pietruszka korzeniowa
drying
natural convection
root parsley
Opis:
Badano wpływ temperatury czynnika suszącego 50, 60 i 70°C i kształtu cząstek pietruszki korzeniowej na kinetykę procesu suszenia w warunkach konwekcji naturalnej. Doświadczalne krzywe suszenia i szybkości suszenia kinetyki suszenia pietruszki w cienkiej warstwie podzielono na dwa etapy, z których końcowy opisano modelem. Określono zakres zmian szybkości suszenia i średnią wartość szybkości suszenia w funkcji zawartości wody.
An influence of the drying-medium temperature 50, 60, 70°C and the shape of the parsley-root particles on the kinetics of the drying process under the conditions of natural convection was investigated. Experimental curves of drying and drying rate kinetics of parsley in a thin layer were divided into two stages, where the final one was determined using a model. The scope of changes in drying and the average drying rate were determined as a function of water content.
Źródło:
Inżynieria Rolnicza; 2005, R. 9, nr 9, 9; 313-320
1429-7264
Pojawia się w:
Inżynieria Rolnicza
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charakterystyka suszarnicza owoców bzu czarnego
Drying characteristics for elder fruits
Autorzy:
Peroń, S.
Surma, M.
Zdrojewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/290090.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Inżynierii Rolniczej
Tematy:
suszenie
owoc
bez czarny
konwekcja naturalna
drying
elder
fruit
natural convection
Opis:
Badano wpływ temperatury suszenia na dynamikę narastania temperatury wnętrza owoców bzu czarnego, szybkość ich wysychania a także ich skurcz suszarniczy i zdolność do rehydracji. Suszenie prowadzono w warunkach konwekcji naturalnej w temperaturach 50, 60, 70°C przy początkowej wilgotności surowca około 75%. Wyniki przedstawiono w postaci wykresów oraz równań korelacyjnych.
The research involved examination of drying temperature impact on the dynamics of temperature rise inside elder fruits, drying rate, and their drying shrinkage and ability to rehydration. Drying was carried out in natural convection conditions at temperatures: 50, 60, 70°C at initial material humidity.
Źródło:
Inżynieria Rolnicza; 2010, R. 14, nr 2, 2; 117-123
1429-7264
Pojawia się w:
Inżynieria Rolnicza
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:
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:
FEM simulation of triple diffusive natural convection along inclined plate in porous medium: prescribed surface heat, solute and nanoparticles flux
Autorzy:
Goyal, M.
Goyal, R
Bhargava, R.
Powiązania:
https://bibliotekanauki.pl/articles/266289.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
triple diffusive
natural convection
nanofluid
binary base fluid
porous medium
solutal concentration flux
nanoparticle concentration flux
inclined plate
naturalna konwekcja
płyn bazowy
nanocząstki
Opis:
In this paper, triple diffusive natural convection under Darcy flow over an inclined plate embedded in a porous medium saturated with a binary base fluid containing nanoparticles and two salts is studied. The model used for the nanofluid is the one which incorporates the effects of Brownian motion and thermophoresis. In addition, the thermal energy equations include regular diffusion and cross-diffusion terms. The vertical surface has the heat, mass and nanoparticle fluxes each prescribed as a power law function of the distance along the wall. The boundary layer equations are transformed into a set of ordinary differential equations with the help of group theory transformations. A wide range of parameter values are chosen to bring out the effect of buoyancy ratio, regular Lewis number and modified Dufour parameters of both salts and nanofluid parameters with varying angle of inclinations. The effects of parameters on the velocity, temperature, solutal and nanoparticles volume fraction profiles, as well as on the important parameters of heat and mass transfer, i.e., the reduced Nusselt, regular and nanofluid Sherwood numbers, are discussed. Such problems find application in extrusion of metals, polymers and ceramics, production of plastic films, insulation of wires and liquid packaging.
Źródło:
International Journal of Applied Mechanics and Engineering; 2017, 22, 4; 883--900
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charakterystyka suszarnicza owoców rokitnika pospolitego poddanych wstępnym zabiegom przygotowawczym
Drying characteristic of common sea-buckthorn subjected to initial preparation treatments
Autorzy:
Peroń, S.
Surma, M.
Zdrojewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/288877.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Inżynierii Rolniczej
Tematy:
suszenie
owoc
rokitnik zwyczajny
konwekcja naturalna
drying
common sea-buckthorn
natural convection
Opis:
Celem pracy było zbadanie dynamiki wysychania owoców rokitnika w warunkach konwekcji naturalnej. Do badań użyto świeżych owoców rokitnika pospolitego o wilgotności ok. 79% - przygotowanych na 3 sposoby - to jest gniecionych, nakłuwanych oraz całych. Suszenie prowadzono w suszarce laboratoryjnej w nieruchomej warstwie przy jej wysokości 3cm i temperaturze 50°C. Wyniki przedstawiono w postaci wykresów oraz równań korelacyjnych.
The purpose of the study was to investigate drying dynamics of the sea-buckthorn fruit in condition of natural convection. Fresh fruit of common sea-buckthorn of 79% moisture content were used for research. They were prepared in three forms- mashed, pricked and whole fruit. Drying process was carried out in a laboratory drier in a motionless layer at 3 cm height and temperature at 50°C. The results were presented in the form of schemes and correlation equations.
Źródło:
Inżynieria Rolnicza; 2011, R. 15, nr 9, 9; 169-176
1429-7264
Pojawia się w:
Inżynieria Rolnicza
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
Tytuł:
Effects of pressure work over a semi-infinite vertical oscillating cylinder
Autorzy:
Sarojini, A.
Palani, G.
Powiązania:
https://bibliotekanauki.pl/articles/1839892.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
cylinder
konwekcja naturalna
metoda Cranka-Nicolsona
finite difference
pressure work
oscillating
skin friction
Opis:
An arithmetical methodology is used to study natural convection with properties of pressure work over a semi-infinite vertical oscillating cylinder. The governing partial differential equations are set up and the resulting equations are changed into a non-dimensional form using the proper non-dimensional quantities. The set of non-dimensional partial differential equations is solved arithmetically using a well-organized method known as the Crank-Nicolson method. The velocity, as well as temperature profiles for different values of parameters are studied with the assistance of graphs.
Źródło:
International Journal of Applied Mechanics and Engineering; 2021, 26, 1; 215-225
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:
Performance of four different nanoparticles in boundary layer flow over a stretching sheet in porous medium driven by buoyancy force
Autorzy:
Ammani Kuttan, B.
Manjunatha, S.
Jayanthi, S.
Gireesha, B. J.
Powiązania:
https://bibliotekanauki.pl/articles/264960.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
konwekcja naturalna
nanociecze
rozwiązania numeryczne
natural convection
porous parameter
nanofluid
numerical solutions
volume fraction
Opis:
This contemporary work explores the theoretical analysis of energy transfer performance of distinct nanoparticles (silver, copper, aluminium oxide and titanium oxide) adjacent to a moving surface under the influence of a porous medium which is driven by the buoyancy force. A mathematical model is presented which is converted to similarity equations by employing similarity transformation. The condensed nonlinear equations were approximated by the iterative method called RKF 45th-order. The flow and energy transference characteristics are explained through graphs and tabulated values. The notable findings are: silver- water is an appropriate nanofluid for enhancing the thermal conductivity of the base fluid. Titanium oxide – water shows a lower fluid flow movement due to porosity.
Źródło:
International Journal of Applied Mechanics and Engineering; 2020, 25, 2; 1-10
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
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