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Wyszukujesz frazę "flow exchange" wg kryterium: Temat


Wyświetlanie 1-9 z 9
Tytuł:
Influence of morphology changes on flow and water exchange in the Odra Estuary
Autorzy:
Jasińska, E.
Powiązania:
https://bibliotekanauki.pl/articles/241071.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
morphology changes
flow exchange
water exchange
Odra estuary
Opis:
Knowledge of the hydrodynamic conditions and the exchange of water in estuaries is important for ecological, navigational and water management reasons. The morpho-logy, river flow, sea level and local winds constitute important factors that influence the water currents and rate and extent of the mixing of salt and fresh water. The influence of the morphology changes on flow conditions, on the penetration of salt into the estuary and on the water exchange in the estuaries in this paper are analysed on the example of the Odra Estuary. The morphology of the Odra Estuary, and specially the Świna Strait, has changed immensely since the beginning of the XVIII century. The analyses were performed on the basis of data from in situ measure-ments and results of calculations. For the calculation the three-dimensional model ESTURO was used, because of the complexity of the hydrodynamic regimes and their three-dimensional character. The calculations were performed for the three different hydro-meteorological conditions for each of the five analysed morphological situations of the Odra Estuary. Some results of calculations have been presented.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2001, 48, 3; 33-57
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the air flow in selected buildings
Autorzy:
Bullová, I.
Powiązania:
https://bibliotekanauki.pl/articles/104898.pdf
Data publikacji:
2018
Wydawca:
Politechnika Rzeszowska im. Ignacego Łukasiewicza. Oficyna Wydawnicza
Tematy:
air flow
aerodynamic coefficient
wind speed
air exchange rate
Opis:
Airflow properties are most apparent adjacent to the surface of the building, because there take place any reactions between liquid and solid object. Air exchange rate is associated with air flow through a building by natural - through small openings and cracks in the structure. Due to leakages in the building construction, opening and closing of windows, the air in the building shifts. The value of air exchange rate is hard to predict and depend of several variables - wind speed, difference between outside and inside temperatures, the quality of the building construction. The paper analyzed the air flow in selected buildings and quantified the value of air pressure differences and the air exchange rate with the emphasis on specification of aerodynamic coefficients.
Źródło:
Czasopismo Inżynierii Lądowej, Środowiska i Architektury; 2018, 65, 1; 161-166
2300-5130
2300-8903
Pojawia się w:
Czasopismo Inżynierii Lądowej, Środowiska i Architektury
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance evaluation of stocks valuation models at MSE
Ocena skuteczności modeli wyceny akcji na MSE
Autorzy:
Ivanovski, Z.
Narasanov, Z.
Ivanovska, N.
Powiązania:
https://bibliotekanauki.pl/articles/2051656.pdf
Data publikacji:
2018
Wydawca:
Akademia Bialska Nauk Stosowanych im. Jana Pawła II w Białej Podlaskiej
Tematy:
stock
cash flow
valuation
discounting
divident
Macedonian Stock Exchange
Opis:
Subject and purpose of work: The main task of this paper is to examine the proximity of valuations generated by different valuation models to stock prices in order to investigate their reliability at Macedonian Stock Exchange (MSE) and to present alternative “scenario” methodology for discounted free cash flow to firm valuation. Materials and methods: By using publicly available data from MSE we are calculating stock prices with three stock valuation models: Discounted Free Cash Flow, Dividend Discount and Relative Valuation. Results: The evaluation of performance of three stock valuation models at the MSE identified that model of Price Multiplies (P/E and other profitability ratios) offer reliable stock values determination and lower level of price errors compared with the average stocks market prices. Conclusions: The Discounted Free Cash Flow (DCF) model provides values close to average market prices, while Dividend Discount (DDM) valuation model generally mispriced stocks at MSE. We suggest the use of DCF model combined with relative valuation models for accurate stocks’ values calculation at MSE.
Przedmiot i cel pracy: Głównym zadaniem tego artykułu jest zbadanie trafności wycen generowanych przez różne modele wyceny cen akcji w celu zbadania ich wiarygodności na Giełdzie Papierów Wartościowych w Macedonii (MSE) oraz przedstawienie alternatywnej metodologii „scenariuszowej” zdyskontowanych wolnych przepływów pieniężnych do wyceny przedsiębiorstw. Materiały i metody: Korzystając z publicznie dostępnych danych z MSE, obliczamy ceny akcji za pomocą trzech modeli wyceny akcji: Zdyskontowanych Przepływów Pieniężnych, Zdyskontowanej Dywidendy i Wyceny Porównawczej. Wyniki: Ocena wydajności trzech modeli wyceny akcji na MSE wykazała, że model Mnożników Cen (P/E i inne wskaźniki rentowności) oferuje rzetelną ocenę wartości akcji i niższy poziom błędów cenowych w porównaniu do średnich cen rynkowych akcji. Wnioski: Model Zdyskontowanych Wolnych Przepływów Pieniężnych (DCF) zapewnia wartości zbliżone do średnich cen rynkowych, podczas gdy model wyceny Zdyskontowanej Dywidendy (DDM) zasadniczo nieprawidłowo wycenia akcje na MSE. Sugerujemy zastosowanie modelu DCF w połączeniu z modelem wyceny porównawczej w celu dokładnego obliczenia wartości akcji na MSE.
Źródło:
Economic and Regional Studies; 2018, 11, 2; 7-23
2083-3725
2451-182X
Pojawia się w:
Economic and Regional Studies
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reactive solute transport in blood flow through a permeable capillary
Autorzy:
Debnath, S.
Roy, A. K.
Bég, O. A.
Powiązania:
https://bibliotekanauki.pl/articles/38695392.pdf
Data publikacji:
2022
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
capillary
axial flow
radial flow
solute dispersion
Gill decomposition
filtration coefficient
exchange coefficient
advection coefficient
Opis:
The present analysis discusses the solute transport process in a steady 2D (axial and radial) laminar flow of blood through a permeable, finite length capillary. Blood is treated as a homogeneous Newtonian fluid and the solute is absorbed at the capillary wall with a linear irreversible reaction rate. The velocity profile is obtained by a regular perturbation technique, whereas the transport coefficients depicted by the Gill generalized dispersion model are solved numerically. A number of different scenarios are considered, namely transport with no-reaction, weak absorption, strong absorption, low filtration or high filtration, etc. In the initial stages, the temporal behaviour of the dispersion coefficient is identical to those cases when there is no radial velocity. For the combined effect of radial and axial velocities, however, the dispersion coefficient is lower for a high absorption rate than for a weak absorption rate. Diffusion is accelerated with higher values of filtration coefficient. Owing to the opposite effects of radial diffusion and radial velocity, the solute particles require more time to reach the steady state. The analysis finds applications in, for example, reactive nutrient and pharmacological transport in capillary hemodynamics.
Źródło:
Archives of Mechanics; 2022, 74, 2-3; 173-200
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of valve-seat angles to operation values and emissions of medium-speed diesel engines
Autorzy:
Marquardt, Leander
Kate, Heiner Joachim
Reinke, Andreas
Kockskämper, Niklas
Powiązania:
https://bibliotekanauki.pl/articles/2204626.pdf
Data publikacji:
2023
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
medium speed engines
gas exchange
valve-seat angle
flow coefficient
thermal load
Opis:
For the development of gas exchange for large diesel engines, a compromise has to be found between efficient valve-flow and the time between overhauls. On the one hand, large effective flow areas, especially during valve-overlap, are demanded. On the other hand, there are limitations of cylinder bore regarding the maximum diameter of inlet and outlet valves and the minimum distance (dead space) between valves and piston, as well as wear-related smaller seat angles. For large medium-speed diesel engines, a valve-seat angle of = ° for inlet and outlet valves is a standard application. For engine-operation with clean fuels, a valve-seat lubrication (gasoil) or smaller seat angles (natural gas) need to be applied. With this presentation, the basic influence of different valve-seat angles on the operation values and emissions will be considered for the example of the single-cylinder research engine FM16/24. Using a self-developed testbed, experimental investigations into effective flow areas as a function of valve-lift at inlet and outlet valves have to be executed. With this input, different cycle calculations including T/C have to be carried out to determine deviances in specific fuel-oil consumption, exhaust-gas temperatures, NOx emissions and air/fuel ratio. The results will be discussed critically.
Źródło:
Acta Mechanica et Automatica; 2023, 17, 2; 173--179
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distribution of heat exchange coefficient and vertical two-phase cross-flow structures examination over tube bundles, using DPIV and electrochemical methods
Badanie nierównomierności rozkładu współczynnika wnikania ciepła na powierzchni rur oraz niejednorodności struktur wokół rur, przy przepływie mieszaniny dwufazowej z wykorzystaniem metody elektrochemicznej i DPIV
Autorzy:
Karaś, M
Zając, D.
Ulbrich, R.
Powiązania:
https://bibliotekanauki.pl/articles/2073407.pdf
Data publikacji:
2013
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
wymiana ciepła
DPIV
elektrochemiczna
przepływ dwufazowy
heat exchange
electrochemical method
two-phase flow
Opis:
Przeprowadzono badania nad przepływem dwufazowym wznoszącym przez przestawny i równoległy pęk rur. Za pomocą cyfrowej anemometrii obrazowej DPIV dokonano wizualizacji przepływu. Do określenia nierównomierności wymiany ciepła na powierzchni rurek wykorzystano elektrochemiczną metodę opartą na analogii wymiany ciepła i masy. Wyniki otrzymane dwiema metodami zestawiono badając wpływ rozkładu pola prędkości wokół rur na intensywność wymiany ciepła na jej powierzchni.
Two-phase vertical flow over a tube bundle was examined. To calculate the heat transfer coefficient on tubes' surface, the electrochemical technique based on heat and mass transfer analogy was used. The Digital Particle Image Velocimetry (DPIV) technique was applied to create velocity fields around tubes. The results obtained using both methods were compared in order to get an overview of velocity distribution around the tube and its influence on heat transfer intensity on its surface.
Źródło:
Inżynieria i Aparatura Chemiczna; 2013, 5; 431--432
0368-0827
Pojawia się w:
Inżynieria i Aparatura Chemiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation of rime icing and its effects on aerodynamic characteristics of an airfoil
Autorzy:
Sznajder, J.
Powiązania:
https://bibliotekanauki.pl/articles/243475.pdf
Data publikacji:
2018
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
computational fluid dynamics
aerodynamics
two-phase flow
simulation of ice accretion
heat exchange
aircraft engineering
transport
vehicle
Opis:
A mathematical model for simulation of icing dedicated to simulation of ice accretion and its effects on aircraft aerodynamic characteristics in conditions of rime icing is presented. Pure rime icing occurs at lower temperatures than glaze icing and results in higher roughness of the surface of deposited ice. The model accounts for increased surface roughness, in terms of equivalent sand grain roughness, caused by deposited rime ice, which influences generation and dispersion of heat in the boundary layer. Increase of surface roughness is determined by analytical models created upon experimental data obtained in icing wind tunnels. Increased generation of heat is a result of increased tangential stress on the surface and is quantified in the temperature recovery factor determined numerically by a CFD solver. Effects of surface roughness on the intensity of forced convection are quantified by application of Colburn analogy between heat and momentum transfer in the boundary layer, which allows assessment of heat transfer coefficient for known friction coefficient, determined by CFD. The computational method includes determination of the surface distribution of mass of captured water in icing conditions. The model of freezing of captured water accounts for generation of heat due to latent heat of captured water droplets, temperature recovery in boundary layer and kinetic energy of captured droplets. The sinks of heat include forced convection, heating of super cooled droplets, conduction of heat through the ice layer and sublimation. The mathematical model is implemented as user-defined function module in ANSYS Fluent solver. The results include effects of deposited ice, including increased surface roughness on aerodynamic characteristics of an airfoil.
Źródło:
Journal of KONES; 2018, 25, 3; 437-443
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Three-dimensional computational fluid dynamics modelling of a proton exchange membrane fuel cell with a serpentine micro-channel design
Autorzy:
Zinko, T.
Jaworski, Z.
Pianko-Oprych, P.
Powiązania:
https://bibliotekanauki.pl/articles/185221.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Proton Exchange Membrane Fuel Cells
Computational Fluid Dynamics
flow field design
polarisation curve
obliczeniowa dynamika płynów
pole przepływu
krzywa polaryzacji
Opis:
The aim of this paper was to demonstrate the feasibility of using a Computational Fluid Dynamics tool for the design of a novel Proton Exchange Membrane Fuel Cell and to investigate the performance of serpentine micro-channel flow fields. A three-dimensional steady state model consisting of momentum, heat, species and charge conservation equations in combination with electrochemical equations has been developed. The design of the PEMFC involved electrolyte membrane, anode and cathode catalyst layers, anode and cathode gas diffusion layers, two collectors and serpentine micro-channels of air and fuel. The distributions of mass fraction, temperature, pressure drop and gas flows through the PEMFC were studied. The current density was predicted in a wide scope of voltage. The current density – voltage curve and power characteristic of the analysed PEMFC design were obtained. A validation study showed that the developed model was able to assess the PEMFC performance.
Źródło:
Chemical and Process Engineering; 2018, 39, 2; 143--154
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flow, waves and water exchange in the Suur Strait, Gulf of Riga, in 2008
Autorzy:
Raudsepp, U.
Laanemets, J.
Haran, G.
Alari, V.
Pavelson, J.
Kouts, T.
Powiązania:
https://bibliotekanauki.pl/articles/49038.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
flow
wave
water exchange
Suur Strait
Riga Gulf
modelling
shear velocity
Baltic Sea
wind
wind condition
storm
wave heigh
sediment
seasonal cycle
horizontal distribution
outflow
Opis:
Wind, flow and wave measurements were performed in November–December in 2008 in the relatively narrow and shallow Suur Strait connecting the waters of the V¨ainameri and the Gulf of Riga. During the measurement period wind conditions were extremely variable, including a severe storm on 23 November. The flow speed along the strait varied between ±0.2 m s−1, except for the 0.4 m s−1 that occurred after the storm as a result of the sea level gradient. The mean and maximum significant wave heights were 0.53 m and 1.6 m respectively. Because of their longer fetch, southerly winds generated higher waves in the strait than winds from the north. All wave events caused by the stronger southerly winds induced sediment resuspension, whereas the current-induced shear velocity slightly exceeded the critical value for resuspension only when the current speed was 0.4 m s−1. A triplenested two-dimensional high resolution (100 m in the Suur Strait) circulation model and the SWAN wave model were used to simulate water exchange in 2008 and the wave-induced shear velocity field in the Suur Strait respectively. Circulation model simulations demonstrated that water exchange was highly variable, that cumulative transport followed an evident seasonal cycle, and that there was an gross annual outflow of 23 km3 from the Gulf of Riga. The horizontal distribution of waveinduced shear velocity during the strong southerly wind event indicated large shear velocities and substantial horizontal variability. The shear velocities were less than the critical value for resuspension in the deep area of the Suur Strait.
Źródło:
Oceanologia; 2011, 53, 1
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-9 z 9

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