Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

English (EN)·Polski (PL)·Yкраїнський (UK)
Przejdź do strony domowej biblioteki Centralna Biblioteka Wojskowa Link otwiera się w nowym oknie Logo biblioteki Prolib Integro - strona głównaCentralna Biblioteka Wojskowa

Wyszukujesz frazę "entropy generation" wg kryterium: Temat

  Lista filtrów
Wyrównaj
Wyświetlanie 1-25 z 26
Tytuł:
Second law optimization and parametric study of a solar air heater having artificially roughened absorber plate
Autorzy:
Sahu, Mukesh Kumar
Prasad, Radha Krishna
Powiązania:
https://bibliotekanauki.pl/articles/240023.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
artificial roughness
entropy generation
entropy generation minimization
augmentation entropy generation number
solar air heater
źródło entropii
minimalizacja
powietrzny kolektor słoneczny
Opis:
In present article a mathematical model of arc shape wire roughened solar air heater, on the basis of energy and exergy output rates, entropy generation rate and augmentation entropy generation number, has been developed. A parametric study leading to entropy generation minimization has also been performed. In the analysis the geometric and operating parameters which have been considered as variable are: inlet air temperature, duct depth, collector width to duct depth ratio, mass flow rate per unit collector area, and temperature rise parameter. Results have been presented to see the effects of these values on the energy and exergy output rates of the roughened solar air heater. Effect of different values of wire rib roughness parameters on entropy generation has also been presented. Finally, design curves and optimization for different rib roughness parameters on the basis of minimum entropy generation number with temperature rise parameter, have been presented and optimum values also have been found out 0.004 to 0.010 (Km2 )/W. The entropy generation rate obtained for the system, in the present work has been compared with those obtained for solar air heater with different roughness geometries on absorber plates available in the literature for common roughness parameters and operating parameters which validate the present results.
Źródło:
Archives of Thermodynamics; 2019, 40, 2; 107-135
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
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:
Entropy generation and thermodynamic analysis of solar air heaters with artificial roughness on absorber plate
Autorzy:
Prasad, R. K.
Sahu, M. K.
Powiązania:
https://bibliotekanauki.pl/articles/240173.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
entropy generation analysis
entropy generation number
irreversibility
Bejan number
analiza generowania entropii
liczba generacyjna entropii
nieodwracalność
liczba Bejana
Opis:
This paper presents mathematical modelling and numerical analysis to evaluate entropy generation analysis (EGA) by considering pressure drop and second law efficiency based on thermodynamics for forced convection heat transfer in rectangular duct of a solar air heater with wire as artificial roughness in the form of arc shape geometry on the absorber plate. The investigation includes evaluations of entropy generation, entropy generation number, Bejan number and irreversibilities of roughened as well as smooth absorber plate solar air heaters to compare the relative performances. Furthermore, effects of various roughness parameters and operating parameters on entropy generation have also been investigated. Entropy generation and irreversibilities (exergy destroyed) has its minimum value at relative roughness height of 0.0422 and relative angle of attack of 0.33, which leads to the maximum exergetic efficiency. Entropy generation and exergy based analyses can be adopted for the evaluation of the overall performance of solar air heaters.
Źródło:
Archives of Thermodynamics; 2017, 38, 3; 23-48
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation in a condenser and related correlations
Autorzy:
Laskowski, R.
Jaworski, M.
Smyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/240683.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
steam condenser
entropy generation
kondensator pary
generowanie entropii
Opis:
The paper presents an analysis of relations describing entropy generation in a condenser of a steam unit. Connections between entropy generation, condenser ratio, and heat exchanger effectiveness, as well as relations implied by them are shown. Theoretical considerations allowed to determine limits of individual parameters which describe the condenser operation. Various relations for average temperature of the cold fluid were compared. All the proposed relations were verified against data obtained using a simulator and actual measurement data from a 200 MW unit condenser. Based on data from a simulator it was examined how the sum of entropy rates, steam condenser effectiveness, terminal temperature difference and condenser ratio vary with the change in the inlet cooling water temperature, mass flow rate of steam and the cooling water mass flow rate.
Źródło:
Archives of Thermodynamics; 2015, 36, 2; 27-48
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Second law analysis of mhd forced convective nanoliquid flow through a two-dimensional channel
Autorzy:
Miri, Rached
Abbassi, Mohamed A.
Ferhi, Mokhtar
Djebali, Ridha
Powiązania:
https://bibliotekanauki.pl/articles/2204682.pdf
Data publikacji:
2022
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
MHD
LBM
channel flow
nanoliquids
entropy generation
Brownian motion
Opis:
The present study deals with fluid flow, heat transfer and entropy generation in a two-dimensional channel filled with Cu–water nanoliquid and containing a hot block. The nanoliquid flow is driven along the channel by a constant velocity and a cold temperature at the inlet, and the partially heated horizontal walls. The aim of this work is to study the influence of the most important parameters such as nanoparticle volume fraction (0%≤ϕ≤4%), nanoparticle diameter (5 nm≤dp≤55 nm), Reynolds number (50≤Re≤200), Hartmann number (0≤Ha≤90), magnetic field inclination angle (0≤γ≤π) and Brownian motion on the hydrodynamic and thermal characteristics and entropy generation. We used the lattice Boltzmann method (LBM: SRT-BGK model) to solve the continuity, momentum and energy equations. The obtained results show that the maximum value of the average Nusselt number is found for case (3) when the hot block is placed between the two hot walls. The minimum value is calculated for case (2) when the hot block is placed between the two insulated walls. The increase in Reynolds and Hartmann numbers enhances the heat transfer and the total entropy generation. In addition, the nanoparticle diameter increase reduces the heat transfer and the irreversibility, the impact of the magnetic field inclination angle on the heat transfer and the total entropy generation is investigated, and the Brownian motion enhances the heat transfer and the total entropy generation.
Źródło:
Acta Mechanica et Automatica; 2022, 16, 4; 417--431
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation on mhd flow of Powell-Eyring fluid between radially stretching rotating disk with diffusion-thermo and thermo-diffusion effects
Autorzy:
Khan, N. A.
Aziz, S.
Ullah, S.
Powiązania:
https://bibliotekanauki.pl/articles/386796.pdf
Data publikacji:
2017
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
axisymmetric flow
entropy generation
stretching disk
Powell-Eyring fluid
diffusion
Opis:
An investigation is performed for an alyzing the effect of entropy generation on the steady, laminar, axisymmetric flow of an incompressible Powell-Eyring fluid. The flow is considered in the presence of vertically applied magnetic field between radially stretching rotating disks. The Energy and concentration equation is taking into account to investigate the heat dissipation, Soret, Dufour and Joule heating effects. To describe the considered flow non-dimensionalized equations, an exact similarity function is used to reduce a set of the partial differential equation into a system of non-linear coupled ordinary differential equation with the associated boundary conditions. Using homotopy analysis method (HAM), an analytic solution for velocity, temperature and concentration profiles are obtained over the entire range of the imperative parameters. The velocity components, concentration and temperature field are used to determine the entropy generation. Plots illustrate important results on the effect of physical flow parameters. Results obtained by means of HAM are then compared with the results obtained by using optimized homotopy analysis method (OHAM). They are in very good agreement.
Źródło:
Acta Mechanica et Automatica; 2017, 11, 1; 20-32
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Maximum entropy generation rate in a heat exchanger at constant inlet parameters
Autorzy:
Laskowski, R.
Jaworski, M.
Powiązania:
https://bibliotekanauki.pl/articles/95303.pdf
Data publikacji:
2017
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
maximum entropy generation rate
entropy
heat exchanger
maksymalna szybkość generowania entropii
entropia
wymiennik ciepła
Opis:
The main goal of the paper is to provide a condition for which a maximum entropy generation occurs in a heat exchanger at constant inlet parameters (temperatures and mass flow rates). Knowing this condition is essential during the design of the heat exchanger as it allows designers to avoid one of its most unfavourable operating conditions in terms of thermodynamics. Entropy generation resulting from the resistance of heat-transferring fluids to flow was not taken into account. Entropy generation was analysed as a function of a heat flow rate at constant parameters at the inlet of a condenser and a counter-flow double-pipe heat exchanger. The analysis showed that for the condenser the entropy generation rate increases with the increase in the heat flow rate. The maximum entropy generation rate occurs for the maximum flow rate of the heat that can be transferred according to the definition of heat transfer effectiveness. For the counter-flow heat exchanger, the entropy generation as a function of the heat flow rate reaches maximum at constant inlet parameters (temperatures and mass flow rates). It appeared that the peak entropy generation, or the largest exergy loss, occurs when the outlet temperatures of the fluids are equal. This assertion was verified against data obtained from a simulator of the counter-flow heat exchanger for two different relations between heat capacity rates.
Źródło:
Journal of Mechanical and Energy Engineering; 2017, 1, 1; 79-86
2544-0780
2544-1671
Pojawia się w:
Journal of Mechanical and Energy Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wpływ parametrów procesu na optymalne warunki pracy nośników katalizatorów stosowanych w procesach selektywnego utleniania i dopalania węglowodorów
Influences of process parameters on optimal working conditions for catalyst carriers in the selective oxidation or incineration of hydrocarbons
Autorzy:
Krajewski, W.
Kalinowski, K.
Najzarek, Z.
Powiązania:
https://bibliotekanauki.pl/articles/357102.pdf
Data publikacji:
2012
Wydawca:
Politechnika Śląska
Tematy:
przepływ ciepła
liczba Bejana
generacja entropii
heat transfer
Bejan number
entropy generation
Opis:
Podano charakterystyki cieplno–przepływowe dla 11 nośników katalizatora. Dla tych nośników wyznaczono optymalne wartości liczb Bejana, przy których stosunek liczb Nusselta do bezwymiarowej szybkości generacji entropii osiąga wartość maksymalną. Te liczby wyznaczono zmieniając kolejno długość złoża, ciśnienie na wylocie ze złoża, temperaturę wlotowa powietrza na złoże i temperaturę ścianki. Podano korelacje na optymalne liczby Bejana w zależności od parametrów procesu. Przedstawiono również takie korelacje na optymalne liczby Reynoldsa oraz wartości maksymalne stosunku liczb Nusselta do bezwymiarowej szybkości generacji entropii.
Heat-flow characteristics for the eleven catalyst carriers are presented. Within these carriers, optimal values of Bejan number were determined for which the maximal ratio of Nusselt number to the dimensionless entropy generation rate attained its maximum. These number values were determined under sequential changing of the bed length, the bed outlet pressure, the air temperature at the bed inlet, and the wall temperature. Correlations are given for the optimal Bejan number, depending on these process parameters. Such correlations are also presented for the optimal Reynolds number, as well as for the maximal ratio of Nusselt number to the dimensionless entropy generation rate.
Źródło:
Archiwum Gospodarki Odpadami i Ochrony Środowiska; 2012, 14, 2; 51-61
1733-4381
Pojawia się w:
Archiwum Gospodarki Odpadami i Ochrony Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exergy balances and entropy generation rates as the mathematical models falsification method Applied for aluminium electrolysis processes
Falsyfikacja modeli matematycznych na podstawie intensywności źródeł entropii na przykładzie procesu elektrolizy aluminium
Autorzy:
Hołda, A.
Kolenda, Z.
Powiązania:
https://bibliotekanauki.pl/articles/355650.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
energy
entropy generation rate
mathematical modeling
energia
szybkość generowania entropii
modelowanie matematyczne
Opis:
A new method of falsification of the mathematical model of the processes taking place inside the aluminium electrolysis cell has been proposed. The method is based on the comparison of the calculation results of the entropy generation rates obtained in theoretical way with the exergy losses estimated from global exergy balance equation. Following irreversible processes have been analyzed - electric current flow, diffusion at the cathode, heat and electric current flow through the anode and cathode, irreversible carbon combustion, heat transfer from electrolyser to the surroundings and convection inside the electrolyte. Exergy balance calculations have been based on the experimental results from industry. The proposed procedure shows good accuracy between mathematical model and experimental data.
W artykule zaproponowano metodę falsyfikacji modelu matematycznego procesów jednostkowych zachodzących w elektrolizerze aluminium poprzez porównanie wartości sumarycznego źródła entropii z wartością strat egzergii wynikającą z zamknięcia globalnego bilansu egzergii. Wiarygodność porównania uścislono poprzez uzgodnienie bilansów substancji i energii. Wyniki obliczeń oparto na bezpośrednich pomiarach przemysłowych. Stwierdzono dobra zgodność modelu matematycznego z wynikami pomiarów.
Źródło:
Archives of Metallurgy and Materials; 2013, 58, 3; 677-682
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimizing Natural Gas Fueling Station Reservoirs Pressure Based on Ideal Gas Model
Autorzy:
Farzaneh-Gord, M.
Deymi-Dashtebayaz, M.
Powiązania:
https://bibliotekanauki.pl/articles/779242.pdf
Data publikacji:
2013
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
compressed natural gas
CNG cylinder
fast filling process
Cascade Reservoirs
thermodynamic analysis
entropy generation
Opis:
At CNG fuelling station, natural gas is usually stored in a cascade storage system to utilize the station more efficient. The cascade storage system is generally divided into three reservoirs, commonly termed low, medium and high-pressure reservoirs. The pressures within these three reservoirs have huge effects on the performance of a CNG fuelling station and a fast filling process of natural gas vehicle’s (NGV) cylinder. A theoretical analysis is developed to study the effects of the reservoirs pressures and temperatures on the performance of the CNG station. The analysis is based on the first and the second law of thermodynamics, conservation of mass and ideal gas assumptions. The results show that as the reservoir temperature decreases, the fill ratio increases and the pressure within the filling station reservoirs has no effects on the fill ratio. The non-dimensional entropy generation and filling time profiles have opposite trends and as entropy generation decreases, the filling time increases. The optimized non-dimensional low and medium pressure-reservoir pressures are found to be as 0.24 and 0.58 respectively in thermodynamic point of view.
Źródło:
Polish Journal of Chemical Technology; 2013, 15, 1; 88-96
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
CuO–water mhd mixed convection analysis and entropy generation minimization in double-lid–driven u-shaped enclosure with discrete heating
Autorzy:
Mliki, Bouchmel
Miri, Rached
Djebali, Ridha
Abbassi, Mohamed A.
Powiązania:
https://bibliotekanauki.pl/articles/2204647.pdf
Data publikacji:
2023
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
U-shaped enclosure
MHD mixed convection
nanoliquids
double lid-driven cavity
entropy generation
LBM
Opis:
The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped enclosure with discrete heat-ing using the lattice Boltzmann method (LBM) numerical method. The nanoliquid thermal conductivity and viscosity are calculated using the Maxwell and Brinkman models respectively. Nanoliquid magnetohydrodynamics (MHD) and mixed convection are analyzed and entropy generation minimisation has been studied. The presented results for isotherms, stream isolines and entropy generation describe the interaction between the various physical phenomena inherent to the problem including the buoyancy, magnetic and shear forces. The operating parameters’ ranges are: Reynolds number (Re: 1–100), Hartman number (Ha: 0–80), magnetic field inclination (γ: 0°–90°), nanoparticles volume fraction (ϕ: 0–0.04) and inclination angle (α: 0°–90°). It was found that the and the total entropy generation augment by increasing Re, ϕ: and γ. conversely, an opposite effect was obtained by increasing Ha and α. The optimum magnetic field and cavity inclination angles to maximum heat transfer are γ = 90° and α = 0.
Źródło:
Acta Mechanica et Automatica; 2023, 17, 1; 112--123
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ocena konstrukcji skraplacza na podstawie minimum strumienia generacji entropii
The condenser design assessment on the basis of the minimum entropy generation
Autorzy:
Laskowski, R.
Rusowicz, A.
Grzebielec, A.
Jaworski, M.
Powiązania:
https://bibliotekanauki.pl/articles/271317.pdf
Data publikacji:
2016
Wydawca:
Centralny Ośrodek Badawczo-Rozwojowy Aparatury Badawczej i Dydaktycznej, COBRABiD
Tematy:
skraplacz
minimum generacji strumienia entropii
ocena konstrukcji skraplacza
condenser
minimum entropy generation
condenser design assessment
Opis:
W skraplaczach energetycznych generowane są jedne z największych strat strumienia entropii w instalacji energetycznej. Celowe jest obniżanie tej straty, aby uzyskać poprawę całkowitej sprawności instalacji. W artykule podano warunek dla minimum generacji strumienia entropii, z którego wynika, że minimum to jest osiągnięte, gdy podgrzew wody w rurkach skraplacza ma równomierny rozkład (przyjmuje taką samą wartość dla wszystkich rurek). Poprawność tego warunku sprawdzono na podstawie danych uzyskanych z symulatora 2D skraplacza dla jednego z krajowych bloków o mocy 50 MW. Na podstawie otrzymanych z symulatora przyrostów temperatur oraz odpowiadających im ciśnień pary dla 30 rurek dokonano oceny poprawności konstrukcji skraplacza.
The losses in power plants condensers are some of the biggest losses in the entropy generation in whole power plant system. It is advisable to decrease the loss for improving the overall efficiency of the system. The article presents the condition for the minimum entropy generation, which states that the minimum is achieved when the heating of the water in the tubes of the condenser has a uniform distribution (takes the same value for all tubes). The correctness of this condition was verified on the basis of data obtained from the 2D condenser simulator for one of the national units with a 50 MW electric capacity. On the basis of the simulator increases temperatures and steam pressures corresponding to 30 tubes assesses the correctness of the construction of the condenser.
Źródło:
Aparatura Badawcza i Dydaktyczna; 2016, 21, 2; 76-84
2392-1765
Pojawia się w:
Aparatura Badawcza i Dydaktyczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Estimation of a tube diameter in a ‘church window’ condenser based on entropy generation minimization
Autorzy:
Laskowski, R.
Rusowicz, A.
Grzebielec, A.
Powiązania:
https://bibliotekanauki.pl/articles/240523.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
entropy generation minimization
power plant condenser
tube diameter
minimalizacja entropii generacji
skraplacz energetyczny
średnica rurek
Opis:
The internal diameter of a tube in a ‘church window’ condenser was estimated using an entropy generation minimization approach. The adopted model took into account the entropy generation due to heat transfer and flow resistance from the cooling-water side. Calculations were performed considering two equations for the flow resistance coefficient for four different roughness values of a condenser tube. Following the analysis, the internal diameter of the tube was obtained in the range of 17.5 mm to 20 mm (the current internal diameter of the condenser tube is 22 mm). The calculated diameter depends on and is positively related to the roughness assumed in the model.
Źródło:
Archives of Thermodynamics; 2015, 36, 3; 49-59
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemically reacting Jeffrey fluid flow over a deformable porous layer with entropy generation analysis
Autorzy:
Das, Utpal Jyoti
Powiązania:
https://bibliotekanauki.pl/articles/2174171.pdf
Data publikacji:
2022
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
odkształcenie
warstwa porowata
dyfuzja termiczna
deformable porous layer
Jeffrey fluid
entropy generation
Bejan number
thermal diffusion
Opis:
Entropy generation of a steady Jeffrey fluid flow over a deformable vertical porous layer is analysed with consideration of a first-order chemical reaction and thermal diffusion. The porous material is modelled as a homogeneous binary mixture of fluid and solid phases where each point in the binary mixture is occupied concurrently by the fluid and solid. The combined phenomenon of solid deformation and fluid movement is taken into account. The impact of relevant parameters on the fluid velocity, solid displacement, temperature and concentration profiles is discussed. It is noticed that the Jeffrey fluid parameter enhances the entropy generation number, fluid velocity and solid displacement profiles, but a reverse effect is seen for the Bejan number. Further, entropy generation, fluid velocity and solid displacement reduce due to the higher estimates of the chemical reaction parameter, while the Bejan number enhances.
Źródło:
International Journal of Applied Mechanics and Engineering; 2022, 27, 3; 36--48
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A study of the local entropy generation rate in a porous media burner
Autorzy:
Mohammadi, I.
Esfahani, J. A.
Kim, K. C.
Powiązania:
https://bibliotekanauki.pl/articles/38597672.pdf
Data publikacji:
2020
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
porous media burner
chemical kinetics
volumetric heat transfer
axisymmetric combustion
local entropy generation
excess air ratio
Opis:
In this paper, the work and performance of the premixed methane-air porous axisymmetrical burner have firstly been simulated numerically using the CFD tools. For this purpose the set of governing equations has been enriched by an additional energy equation in porous solid, and the chemical species transport has been extended onto the multi-step mechanism (GRI-2-11). This numerical model has been verified on the base of available benchmark experiments. Next, we have studied the local entropy generation problem taking into account not only classical contributions like viscous and turbulent dissipation but also, the porous combustion of gases. The results showed that the greatest portion of entropy generation in the porous medium burner is related to chemical reactions, followed by heat transfer, mass diffusion (mixing) and friction (viscous dissipation), respectively. According to the results, as the excess air ratio increases, the local entropy generation rate due to heat transfer and friction increases and the local entropy generation rate due to chemical reactions is decreased. Also, by increasing the volumetric heat transfer coefficient, the local entropy generation rate due to heat transfer decreases and the local entropy generation rate due to friction and chemical reactions increases. Also, the local entropy generation rate due to mixing does not show a significant change with the changing excess air ratio and volumetric heat transfer coefficient.
Źródło:
Archives of Mechanics; 2020, 72, 3; 257-279
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation due to non-Newtonian fluid flow in annular pipe with relative rotation: constant viscosity case
Generacja entropii przy przepływie indukowanym względnym ruchem obrotowym ścian pierścieniowego przewodu - przypadek przepływu o stałej lepkości
Autorzy:
Kahraman, A.
Yurusoy, M.
Powiązania:
https://bibliotekanauki.pl/articles/281786.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
nieniutonowskie ciecze
płyny trzeciego stopnia
liczba generacyjna entropii
non-Newtonian fluid
third grade fluid
entropy generation number
Opis:
Entropy generation due non-Newtonian fluid flow in an annular pipe with relative rotation is investigated. A third grade fluid with constant viscosity is accommodated in the analysis. Relative rotational motion is present between inner and outer cylinders, which induces the flow. Analytical solutions for velocity and temperature distributions are presented, and entropy generation number is computed for different dimensionless values of non-Newtonian viscosity, Brinkman’s number and velocity ratio. It is found that the increasing of dimensionless non-Newtonian viscosity lowers the number entropy generation. This is more pronounced in the region close to the annular pipe inner wall. The increasing of Brinkman’s number enhances the number entropy generation, particularly in the vicinity of the annular pipe inner wall.
W pracy zbadano zagadnienie generacji entropii obserwowanej podczas przepływu nieniutonowskiej cieczy przez przewód pierścieniowy, którego ścianki obracają się względem siebie. Do analizy przyjęto płyn trzeciego stopnia o stałej lepkości. Przepływ czynnika jest indukowany względnym ruchem obrotowym zewnętrznego i wewnętrznego cylindra tworzącego ścianki przewodu. Rozwiązania analityczne zaprezentowano dla rozkładu prędkości i temperatury płynu, a liczbę generacyjną entropii wyznaczono dla różnych wartości lepkości nieniutonowskiej cieczy, liczby Birnkmana i stosunku prędkości obwodowej cylindrów. Potwierdzono, że zwiększenie bezwymiarowej lepkości obniża liczbę generacyjną entropii. Ten efekt jest szczególnie wyraźny w obszarze bliskim ściany wewnętrznego cylindra. Wzrost liczby Birnkmana powiększa liczbę generacyjną entropii, także w pobliżu ściany wewnętrznej przewodu.
Źródło:
Journal of Theoretical and Applied Mechanics; 2008, 46, 1; 69-83
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation minimization in transient heat conduction processes PART II – Transient heat conduction in solids
Autorzy:
Kolenda, Z. S.
Szmyd, J. S.
Powiązania:
https://bibliotekanauki.pl/articles/201936.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
transient heat conduction
initial boundary value problem
entropy generation minimization
przewodzenia ciepła
początkowa wartość graniczna
minimalizacja entropii generacji
Opis:
Formulation and solution of the initial boundary-value problem of heat conduction in solids have been presented when an entropy generation minimization principle is imposed as the arbitrary constraint. Using an entropy balance equation and the Euler-Lagrange variational approach a new form of the heat conduction equation (non-linear partial difference equation) is derived.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2014, 62, 4; 883-887
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical analysis of structure, stability and entropy generation in biogas coflow diffusion flames
Autorzy:
Kumar, R. Nivethana
Kumaran, S. Muthu
Raghavan, Vasudevan
Powiązania:
https://bibliotekanauki.pl/articles/2065757.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
biogas
flame stability
entropy generation
coflow air
hydrogen injection
preheated reactant
biogaz
stabilność płomienia
generowanie entropii
wtrysk wodoru
Opis:
Biogas is a gaseous biofuel predominantly composed of methane and carbon-dioxide. Stability of biogas flames strongly depend upon the amount of carbon-dioxide present in biogas, which varies with the source of biomass and reactor. In this paper, a comprehensive study on the stability and flame characteristics of coflow biogas diffusion flames is reported. Numerical simulations are carried out using reactive flow module in OpenFOAM, incorporated with variable thermophysical properties, Fick’s and Soret diffusion, and short chemical kinetics mechanism. Effects of carbon-dioxide content in the biogas, temperatures of the fuel or coflowing air streams (preheated reactant) and hydrogen addition to fuel or air streams are analyzed. Entropy generation in these flames is also predicted. Results show that the flame temperature increases with the degree of preheat of reactants and the flames show better stability with the preheated air stream. Preheating the air contributes to increased flame stability and also to a significant decrease in entropy generation. Hydrogen addition, contributing to the same power rating, is seen to be relatively more effective in increasing the flame stability when added to the fuel stream. Results in terms of flow, temperature, species and entropy fields, are used to describe the stability and flame characteristics.
Źródło:
Archive of Mechanical Engineering; 2022, LXIX, 1; 99--128
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal and hydraulic phenomena in boundary layer of minijets impingement on curved surfaces
Autorzy:
Kura, T.
Fornalik-Wajs, E.
Wajs, J.
Powiązania:
https://bibliotekanauki.pl/articles/240656.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
jet impingement
minijets array
boundary layer
entropy generation
Nusselt number
uderzenie
strumień
warstwa przyścienna
generowanie entropii
liczby Nusselta
Opis:
Presented work considers flow and thermal phenomena occurring during the single minijet impingement on curved surfaces, heated with a constant heat flux, as well as the array of minijets. Numerical analyses, based on the mass, momentum and energy conservation laws, were conducted, regarding single phase and two-phase simulations. Focus was placed on the proper model construction, in which turbulence and boundary layer modeling was crucial. Calculations were done for various inlet parameters. Initial single minijet results served as the basis for the main calculations, which were conducted for two jet arrays, with flat and curved heated surfaces. Such complex geometries came from the cooling systems of electrical devices, and the geometry of cylindrical heat exchanger. The results, regarding Nusselt number, heated surface temperature, turbulence kinetic energy, production of entropy and vorticity, were presented and discussed. For assumed geometrical parameters similar results were obtained.
Źródło:
Archives of Thermodynamics; 2018, 39, 1; 147-166
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neuro-genetic optimization of ribbed heat exchanger using entropy augmentation generation number
Autorzy:
Konchada, Pavan K.
Sukhvinder, Bhatti
Relangi, Siddhardha
Chekuri, Rambhadriraju
Powiązania:
https://bibliotekanauki.pl/articles/240035.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
rib
square duct
entropy augmentation generation number
artificial neural network
micro genetic algorithm
Opis:
Numerical predictions of heat transfer under laminar conditions in a square duct with ribs are presented in this paper. Ribs are provided on top and bottom walls in a square duct in a staggered manner. The flow rates have been varied between Reynolds number 200 and 600. Various configurations of ribs by varying length, width and depth have been investigated for their effect on heat transfer, friction factor and entropy augmentation generation number. Further artificial neural network integrated with genetic algorithm was used to minimize the entropy augmentation generation number (performance factor) by selecting the optimum rib dimensions in a selected range. Genetic algorithm is compared with microgenetic algorithm to examine the reduction in computational time for outlay of solution accuracy.
Źródło:
Archives of Thermodynamics; 2020, 41, 2; 169-184
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transient velocity and steady state entropy generation in a microfluidic Couette flow containing charged nano particles
Autorzy:
Gorla, R. S. R.
Gireesha, B. J.
Powiązania:
https://bibliotekanauki.pl/articles/264851.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
transient velocity
steady state entropy generation
microfluidic Couette flow
charged nanoparticles
Bejan number and Brinkman number
przepływ Couette'a
liczba Brinkmana
nanocząsteczki
Opis:
An analysis has been provided to determine the transient velocity and steady state entropy generation in a microfluidic Couette flow influenced by electro-kinetic effect of charged nanoparticles. The equation for calculating the Couette flow velocity profile is derived for transient flow. The solutions for momentum and energy equations are used to get the exact solution for the dimensionless velocity ratio and dimensionless entropy generation number. The effects of the dimensionless entropy generation number, Bejan number, irreversibility ratio, entropy generation due to fluid friction and due to heat transfer on dimensionless time, relative channel height, Brinkman number, dimensionless temperature ratio, nanoparticle volume fraction are analyzed.
Źródło:
International Journal of Applied Mechanics and Engineering; 2015, 20, 4; 787-804
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical analysis of entropy generation in longitudinally finned tube heat exchanger with shell side nanofluid by a single phase approach
Autorzy:
Konchada, P. K.
Pv, V.
Bhemuni, V.
Powiązania:
https://bibliotekanauki.pl/articles/240513.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
longitudinal finned tube heat exchanger
user functions and CEL Expressions
ANSYS CFX
Taguchi
entropy generation
wymiennik ciepła
rury żebrowane
funkcje użytkownika
generowanie entropii
Opis:
The presence of nanoparticles in heat exchangers ascertained increment in heat transfer. The present work focuses on heat transfer in a longitudinal finned tube heat exchanger. Experimentation is done on longitudinal finned tube heat exchanger with pure water as working fluid and the outcome is compared numerically using computational fluid dynamics (CFD) package based on finite volume method for different flow rates. Further 0.8% volume fraction of aluminum oxide (Al2O3) nanofluid is considered on shell side. The simulated nanofluid analysis has been carried out using single phase approach in CFD by updating the user-defined functions and expressions with thermophysical properties of the selected nanofluid. These results are thereafter compared against the results obtained for pure water as shell side fluid. Entropy generated due to heat transfer and fluid flow is calculated for the nanofluid. Analysis of entropy generation is carried out using the Taguchi technique. Analysis of variance (ANOVA) results show that the inlet temperature on shell side has more pronounced effect on entropy generation.
Źródło:
Archives of Thermodynamics; 2016, 37, 2; 3-22
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation minimization in steady-state and transient diffusional heat conduction processes Part I – Steady-state boundary value problem
Autorzy:
Kolenda, Z. S.
Szmyd, J. S.
Huber, J.
Powiązania:
https://bibliotekanauki.pl/articles/200901.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat conduction
entropy generation
boundary value problems
Euler-Lagrange variational equation
przewodzenia ciepła
generacja entropii
problemy granica -wartość
wariacyjne równanie Eulera-Lagrange'a
Opis:
An application of the Entropy Generation Minimization principle allows new formulation of the boundary and initial boundaryvalue problems. Applying Euler-Lagrange variational formalism new mathematical form of heat conduction equation describing steady-state processes have been derived. Mathematical method presented in the paper can also be used for any diffusion heat and mass transfer process. Linear and non-linear problems with internal heat sources have been analyzed.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2014, 62, 4; 875-882
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation and squeezing flow past a Riga plate with Cattaneo-Christov heat flux
Autorzy:
Atlas, M.
Hussain, S.
Sagheer, M.
Powiązania:
https://bibliotekanauki.pl/articles/202419.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nanowłókna
konwekcyjne warunki brzegowe
strumień ciepła Cattaneo-Christova
generowanie entropii
squeezing flow
Riga plate
nanofluids
convective boundary conditions
Cattaneo-Christov heat flux
entropy generation
Opis:
In this article, we investigate the convective heat transfer of the two-dimensional unsteady squeezing flow past a Riga plate. To examine the heat transfer, Cattaneo-Christov heat flux model is used. Influence of entropy generation on heat transfer has been investigated numerically. With the help of suitable similarity transformation, the governing partial differential equations (PDEs) are converted into ordinary differential equations (ODEs). The obtained system of non-linear ordinary differential equations subject to the convective boundary conditions is solved by the shooting method using the computational software MATLAB. To strengthen the reliability of the results obtained by the shooting method, the MATLAB built-in function bvp4c has been used. The graphs show the effect of different physical parameters for velocity, temperature, concentration and tables are presented to observe the behaviour of skin friction and sherwood number under the influence of certain physical parameters. It is observed that for increasing values of thermal relaxation parameter, the temperature profile increases and an opposite behaviour is shown for the concentration profile. Moreover, with an increase in the Brinkman number, the entropy generation increases.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2018, 66, 3; 291-300
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy analysis of third-grade MHD convection flows from a horizontal cylinder with slip
Autorzy:
Madhavi, K.
Prasad, V. R.
Gaffar, S. A.
Venkatadri, K.
Powiązania:
https://bibliotekanauki.pl/articles/139843.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
third-grade viscoelastic fluid model
thermal jump
entropy generation
Bejan number
Hartmann number
lepkosprężysty model cieczy trzeciego stopnia
skok termiczny
generowanie entropii
liczba Bejana
liczba Hartmanna
Opis:
In thermos fluid dynamics, free convection flows external to different geometries, such as cylinders, ellipses, spheres, curved walls, wavy plates, cones, etc., play major role in various industrial and process engineering systems. The thermal buoyancy force associated with natural convection flows can play a critical role in determining skin friction and heat transfer rates at the boundary. In thermal engineering, natural convection flows from cylindrical bodies has gained exceptional interest. In this article, we mathematically evaluate an entropy analysis of magnetohydrodynamic third-grade convection flows from permeable cylinder considering velocity and thermal slip effects. The resulting non-linear coupled partial differential conservation equations with associated boundary conditions are solved with an efficient unconditionally stable implicit finite difference Keller-Box technique. The impacts of momentum and heat transport coefficients, entropy generation and Bejan number are computed for several values of non-dimensional parameters arising in the flow equations. Streamlines are plotted to analyze the heat transport process in a two-dimensional domain. Furthermore, the deviations of the flow variables are compared with those computed for a Newtonian fluid and this has important implications in industrial thermal material processing operations, aviation technology, different enterprises, energy systems and thermal enhancement of industrial flow processes.
Źródło:
Archive of Mechanical Engineering; 2018, LXV, 3; 417-440
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-25 z 26

Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies