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Wyszukujesz frazę "void fraction" wg kryterium: Temat

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    Wyświetlanie 1-10 z 10
    Tytuł:
    Determination of the temperature field using liquid crystal thermography and analysis of two-phase flow structures in research on boiling heat transfer in a minichannel
    Autorzy:
    Piasecka, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/220691.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    temperature measurement
    liquid crystal thermography
    measurement accuracy
    void fraction
    Opis:
    The paper presents the application of liquid crystal thermography for temperature determination and visualisation of two phase flow images on the studied surface. Properties and applications of thermochromic liquid crystals are discussed. Liquid crystals were applied for two-dimensional detection of the temperature of the heating foil forming one of the surfaces of the minichannel along which the cooling liquid flowed. The heat flux supplied to the heating surface was altered in the investigation and it was accompanied by a change in the color distribution on the surface. The accuracy of temperature measurements on the surface with liquid crystal thermography is estimated. The method of visualisation of two-phase flow structures is described. The analysis of monochrome images of flow structures was employed to calculate the void fraction for some cross-sections. The flow structure photos were processed using Corel graphics software and binarized. The analysis of phase volumes employed Techsystem Globe software. The measurement error of void fraction is estimated.
    Źródło:
    Metrology and Measurement Systems; 2013, 20, 2; 205-216
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental investigations into the impact of the void fraction on the condensation characteristics of R134a refrigerant in minichannels under conditions of periodic instability
    Autorzy:
    Kuczyński, W.
    Charun, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/240014.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    kondensacja
    minikanały
    okresowe niestabilności
    udział objętościowy
    condensation
    minichannels
    Periodic instabilities
    void fraction
    Opis:
    This paper present the results of experimental investigations of condensation of R134a refrigerant in pipe minichannels with internal diameters 0.64, 0.90, 1.40, 1.44, 1.92 and 3.30 mm subject to periodic pressure instabilities. It was established that as in conventional channels, the displacement velocity of the pressure instabilities distinctly depends on the frequency of their hydrodynamic generation. The void fraction distinctly influences the velocity of the pressure instabilities. The form of this relationship depends on the internal diameter of the minichannels and on the method of calculating the void fraction.
    Źródło:
    Archives of Thermodynamics; 2011, 32, 2; 21-37
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Designing a simple radiometric system to predict void fraction percentage independent of flow pattern using radial basis function
    Autorzy:
    Roshani, G. H.
    Nazemi, E.
    Shama, F.
    Imani, M. A.
    Mohammadi, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/221419.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    two-phase flow
    gamma-ray attenuation
    scintillation detector
    void fraction
    artificial neural network
    Opis:
    The void fraction is one of the most important parameters characterizing a multiphase flow. The prediction of the performance of any system operating with more than single phase relies on our knowledge and ability to measure the void fraction. In this work, a validated simulation study was performed in order to predict the void fraction independent of the flow pattern in gas-liquid two-phase flows using a gamma ray 60Co source and just one scintillation detector with the help of an artificial neural network (ANN) model of radial basis function (RBF). Three used inputs of ANN include a registered count under Compton continuum and counts under full energy peaks of 1173 and 1333 keV. The output is a void fraction percentage. Applying this methodology, the percentage of void fraction independent of the flow pattern of a gas-liquid two-phase flow was estimated with a mean relative error less than 1.17%. Although the error obtained in this study is almost close to those obtained in other similar works, only one detector was used, while in the previous studies at least two detectors were employed. Advantages of using fewer detectors are: cost reduction and system simplification.
    Źródło:
    Metrology and Measurement Systems; 2018, 25, 2; 347-358
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of liquid-gas flow in pipeline using gamma-ray absorption technique and advanced signal processing
    Autorzy:
    Hanus, Robert
    Zych, Marcin
    Mosorov, Volodymyr
    Golijanek-Jędrzejczyk, Anna
    Jaszczur, Marek
    Andruszkiewicz, Artur
    Powiązania:
    https://bibliotekanauki.pl/articles/1848957.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    two-phase flow
    void fraction
    gamma-ray absorption
    flow regime identification
    artificial neural network
    Opis:
    Liquid-gas flows in pipelines appear in many industrial processes, e.g. in the nuclear, mining, and oil industry. The gamma-absorption technique is one of the methods that can be successfully applied to study such flows. This paper presents the use of the gamma-absorption method to determine the water-air flow parameters in a horizontal pipeline. Three flow types were studied in this work: plug, transitional plug-bubble, and bubble one. In the research, a radiometric set consisting of two Am-241 sources and two NaI(TI) scintillation detectors have been applied. Based on the analysis of the signals from both scintillation detectors, the gas phase velocity was calculated using the cross-correlation method (CCM). The signal from one detector was used to determine the void fraction and to recognise the flow regime. In the latter case, a Multi-Layer Perceptron-type artificial neural network (ANN) was applied. To reduce the number of signal features, the principal component analysis (PCA) was used. The expanded uncertainties of gas velocity and void fraction obtained for the flow types studied in this paper did not exceed 4.3% and 7.4% respectively. All three types of analyzed flows were recognised with 100% accuracy. Results of the experiments confirm the usefulness of the gamma-ray absorption method in combination with radiometric signal analysis by CCM and ANN with PCA for comprehensive analysis of liquid-gas flow in the pipeline.
    Źródło:
    Metrology and Measurement Systems; 2021, 28, 1; 145-159
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Void fraction and flow regime determination by means of MCNP code and neural network
    Autorzy:
    Rabiei, A.
    Shamsaei, M.
    Kafaee, M.
    Shafaei, M.
    Mahdavi, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/146656.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    flow regime
    gamma-ray densitometry
    neural network (NN)
    Monte Carlo N-particle (MCNP)
    void fraction
    Opis:
    One of the non-intrusive and accurate methods of measuring void fraction in two-phase gas liquid pipe flows is the use of the gamma-transmission void fraction measurement technique. The goal of this study is to describe low-energy gamma-ray densitometry using an 241Am source for the determination of void fraction and flow regime in water/gas pipes. The MCNP code was utilized to simulate electron and photon transport through materials with various geometries. Then, a neural network was used to convert multi-beam gamma-ray spectra into a classification of the flow regime and void fraction. The simulations cover the full range of void fraction with Bubbly, Annular and Droplet flows. By using simulation data as input to the neural networks, the void fraction was determined with an error less than 3% regardless of the flow regime. It has thus been shown that multi-beam gamma-ray densitometers with a detector response examined by neural networks can analyze a two-phase flow with high accuracy.
    Źródło:
    Nukleonika; 2012, 57, 3; 345-349
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measurements of two-phase flow patterns and local void fraction in vertical rectangular minichannel
    Autorzy:
    Kaniowski, R.
    Poniewski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/240074.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    boiling
    minichannel
    two-phase flow pattern
    void fraction
    wrzenie
    minikanał
    model przepływu dwufazowego
    udział objętościowy
    Opis:
    Technology advancements entail a necessity to remove huge amounts of heat produced by today’s electronic devices based on highly integrated circuits, major generators of heat. Heat transfer to boiling liquid flowing through narrow minichannels is a modern solution to the problem of heat transfer enhancement. The study was conducted for FC-72 boiling in a rectangular, vertical and asymmetrically heated minichannel that had depths of 0.5–1.5 mm, a width of 20 mm and a length of 360 mm. The heat flux increased and decreased within the range of 58.3–132.0 kWm-2, the absolute pressure ranged from 0.116 to 0.184 MPa and the mass flux was 185–1139.2 kgm-2s-1. The boiling process took place on a flat vertical heating surface made of Haynes-230 0.1 mm thick acid-proof rolled plate with the surface roughness of 121 μm.
    Źródło:
    Archives of Thermodynamics; 2013, 34, 2; 3-21
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Design and simulation of a multienergy gamma ray absorptiometry system for multiphase flow metering with accurate void fraction and water-liquid ratio approximation
    Autorzy:
    Khayat, Omid
    Afarideh, Hossein
    Powiązania:
    https://bibliotekanauki.pl/articles/147267.pdf
    Data publikacji:
    2019
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    multiphase flow measurement
    void fraction
    water-liquid ratio
    flow regime
    MCNP
    artificial neural network
    reżim przepływu
    sztuczna sieć neuronowa
    Opis:
    Multiphase flow meters are used to measure the water-liquid ratio (WLR) and void fraction in a multiphase fluid stream pipeline. In the present study, a system of multiphase flow measurement has been designed by application of three thallium-doped sodium iodide scintillators and a radioactive source of 133Ba simulated by Monte Carlo N-particle (MCNP) transport code. In order to capture radiations passing across the pipe, two direct detectors have been installed on opposite sides of the radioactive source. Another detector has been placed perpendicular to the transmission beam emitted from the 133Ba source to receive radiations scattered from the fluid flow. Simulation was done by the MCNP code for different volumetric fractions of water, oil, and gas phases for two types of flow regimes, namely, homogeneous and annular; training and validation data have been provided for the artificial neural network (ANN) to develop a computation model for pattern recognition. Depending on applications of the neural system, several structures of ANNs are used in the current paper to model the flow measurement relations, while the detector outputs are considered as the input parameters of the neural networks. The first, second, and third structures benefit from two, three, and five multilayer perceptron neural networks, respectively. Increasing the number of ANNs makes the system more complicated and decreases the available data; however, it increases the accuracy of estimation of WLR and gas void fraction. According to the results, the maximum relative difference was observed in the scattering detector. It was clear that transmission detectors would demonstrate the difference between the flow regimes as well. It is necessary to note that the error calculated by the MCNP simulator is <0.5% for the direct detectors (TR1 and TR2). Due to the difference between the data of the two flow regimes and the errors of data in the simulation codes of the MCNP, it was possible to separate these flow regimes. The effect of changing WLR on the efficiency for a constant void fraction confi rms a considerable variance in the results of annular and homogeneous flow s occurring in the scattering detector. There is a similar trend for the void fraction; hence, one can easily distinguish changes in efficiency due to the WLR. Analysis of the simulation results revealed that in the proposed structure of the multiphase flow meter and the computation model used for simulation, the two flow regimes are simply distinguishable.
    Źródło:
    Nukleonika; 2019, 64, 1; 19-29
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental determination of the void volume fraction for S235JR steel at failure in the range of high stress triaxialities
    Autorzy:
    Kossakowski, P. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/354784.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    failure
    critical void volume fraction
    Gurson-Tvergaard-Needleman material model
    S235JR steel
    high stress triaxiality
    Opis:
    This paper is concerned with the critical void volume fraction fF representing the size of microdefects in a material at the time of failure. The parameter is one of the constants of the Gurson-Tvergaard-Needleman (GTN) material model that need to be determined while modelling material failure processes. In this paper, an original experimental method is proposed to determine the values of fF. The material studied was S235JR steel. After tensile tests, the void volume fraction was measured at the fracture surface using an advanced technique of quantitative image analysis The material was subjected to high initial stress triaxialities T0 ranging from 0.556 to 1.345. The failure processes in S235JR steel were analysed taking into account the influence of the state of stress.
    Źródło:
    Archives of Metallurgy and Materials; 2017, 62, 1; 167-172
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of initial porosity on material response under multi-axial stress state for S235JR steel
    Autorzy:
    Kossakowski, P. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/230606.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    porowatość początkowa
    objętość pustek początkowa
    model materiałowy Gurson-Tvergaard-Needleman
    stany naprężeń wieloosiowe
    naprężenie trójosiowe duże
    pustki
    obliczenia numeryczne
    stal S235JR
    initial porosity
    initial void volume fraction
    Gurson-Tvergaard-Needleman material model
    multi-axial stress states
    high stress triaxiality
    voids
    numerical calculations
    S235JR steel
    Opis:
    The effect of the initial porosity on the material response under multi-axial stress state for S235JR steel using the Gurson-Tvergaard-Needleman (GTN) material model was examined. Three levels of initial porosity, defined by the void volume fraction f0, were considered: zero porosity for fully dense material without pores, average and maximum porosity according to the metallurgical requirements for S235JR steel. The effect of the initial porosity on the material response was noticed for tensile elements under multi-axial stress state defined by high stress triaxiality sigma m/sigma e = 1.345. This effect was especially noticeable at the range of the material failure. In terms of the load-bearing capacity of the elements, the conservative results were obtained when maximum value of f0 = 0.0024 was used for S235JR steel under multi-axial stress state, and this value is recommended to use in the calculations in order to preserve the highest safety level of the structure. In usual engineering calculations, the average porosity defined by f0 = 0.001 may be applied for S235JR.
    Źródło:
    Archives of Civil Engineering; 2012, 58, 4; 445-462
    1230-2945
    Pojawia się w:
    Archives of Civil Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of the void volume fraction for S235JR steel at failure for low initial stress triaxiality
    Analiza krytycznego udziału objętościowego pustek w momencie zniszczenia stali S235JR przy niskim wstępnym stopniu trójosiowości naprężeń
    Autorzy:
    Kossakowski, P. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/230529.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    udział objętościowy
    pustka
    zniszczenie
    stal S235JR
    model Gursona-Tvergaarda-Needlemana
    naprężenie małe
    trójosiowość naprężeń
    volume fraction
    void
    failure
    S235JR steel
    Gurson-Tvergaard-Needleman model
    low stress
    stress triaxiality
    Opis:
    This paper deals with problems of failure mechanisms of S235JR structural steel. One of the fundamental parameters of the Gurson-Tvergaard-Needleman damage mechanics-based material model is considered in order to describe the behaviour of the material at the plastic range. The analysis was performed on the void volume fraction fF determined at failure of S235JR steel. The case of low initial stress triaxiality η = 1/3 was taken into consideration. Different from the most popular methods such as curve-fitting, the experimental method based on the digital image analysis of the fracture surface of S235JR steel is proposed in order to determine the critical parameter fF.
    Tematem pracy są zagadnienia związane z mechanizmami towarzyszącymi procesowi niszczenia stali konstrukcyjnej S235JR. Zakres badań obejmował końcową fazę uplastycznienia materiału, aż do momentu jego zniszczenia. W przeprowadzonej analizie oparto się na podejściu mechaniki zniszczenia, wykorzystując model materiału porowatego Gursona-Tvergaarda-Needlemana (GTN). Zbadano jeden z podstawowych parametrów mikrostruktury GTN, krytyczny udział objętościowy pustek fF. Współczynnik ten determinuje proces niszczenia materiału od chwili wzrostu i łączenia się mikrodefektów struktury materiałowej, aż do dekohezji materiału w skali makro. Badania przeprowadzono dla przypadku niskiego wstępnego stopnia trójosiowości naprężeńη = 1/3. W odróżnieniu od najpopularniejszych metod, takich jak np. procedura dopasowania parametrów analizy do krzywych wzorcowych, zaproponowano metodę eksperymentalną, opartą na analizie rzeczywistych obrazów powierzchni pęknięć stali S235JR uzyskanych doświadczalnie. Cyfrowa analiza obrazowa powierzchni pęknięć pozwoliła na określenie wartości udziału objętościowego pustek fF w momencie zniszczenia materiału, co umożliwiło eksperymentalne wyznaczenie krytycznego parametru fF dla stali S235JR. W pracy przedstawiono również wyniki analizy numerycznej, weryfikującej rezultaty uzyskane w badaniach doświadczalnych. Symulowano przypadek rozciągania statycznego elementu o przekroju kołowym, który modelowano przy zastosowaniu modelu materiału GTN. Wyznaczone wartości parametru fF pozwoliły na symulację procesu uplastycznienia stali S235JR oraz przewidzenie momentu jej zniszczenia.
    Źródło:
    Archives of Civil Engineering; 2018, 64, 1; 101-115
    1230-2945
    Pojawia się w:
    Archives of Civil Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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