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    Wyświetlanie 1-13 z 13
    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 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:
    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:
    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:
    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:
    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 1-13 z 13

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