Wyniki wyszukiwania - Biblioteka Nauki

1

Tomographic measurement techniques : visualization of multiphase flows

100%

Lorcher M. , Schmitz D. , Mewes D.

|

tom Vol. 8, No. 4

667-679

EN

A tomographic measurement technique is applied for visualization of the local void fraction in the two phase flow of air and water in the mixing chamber of a two-phase-nizzle. With this measurement technique a high spatial and temporal resolution can be achieved. The measured physical property is the electric conductivity of the water. The conductivity is measured with pairs of wires strained in the investigated cross section. The measurement values are proportional to ralative liquid fraction. With an algebraic reconstruction technique (ART) the field of the liquid fraction in the investigated cross-section in calculated from the measurement values. The quality of the reconstruction is increased by a-priori-knowledge.

2

Void fraction and flow regime determination by means of MCNP code and neural network

88%

Rabiei A. , Shamsaei M. , Kafaee M. , Shafaei M. , Mahdavi N.

|

tom Vol. 57, No. 3

345-349

EN

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.

3

Evaluation of liquid-gas flow in pipeline using gamma-ray absorption technique and advanced signal processing

88%

Hanus R. , Zych M. , Mosorov V. , Golijanek-Jędrzejczyk A. , Jaszczur M. , Andruszkiewicz A.

Metrology and Measurement Systems

|

2021

|

tom Vol. 28, nr 1

145--159

EN

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.

4

Capacitance sensor for void fraction measurement

88%

Krupa A. , Jaworek A.

|

tom R. 86, nr 7

196-198

PL

Wyznaczono charakterystyki pomiarowe przetwornika pojemnościowego do pomiaru stopnia zapełnienia w przepływach dwufazowych o strukturze korkowej, pierścieniowej i pęcherzowej. Przetwornik pojemnościowy składa się z dwóch elektrod umieszczonych na zewnętrznej ściance rury. Zmiany pojemności przetwornika spowodowane zmianą zawartości faz w przepływie mierzone są w obwodzie rezonansowym generatora w.cz. Zmiany częstotliwości generatora są miarą zawartości fazy gazowej w rurze.

EN

Characteristics of capacitance sensor used for void fraction measurements in two phase flow of slug, annular or bubble flows patterns have been determined. The sensor consists of two electrodes mounted on outer side of the pipeline. The capacitance changes due to void fraction variations were measured in a radio-frequency resonant circuit. The frequency deviations are the measure of void fraction in the pipeline.

5

Udziały objętościowe faz w przepływie trójfazowym powietrze - woda - olej w rurach pionowych

75%

Nowak M. , Troniewski L. , Witczak S.

|

2006

|

tom Nr 6s

168-169

EN

An attempt to connect the gas void fraction with flow patterns in three-phase air - water - oil flow was undertaken in the paper. A comparison of the measured and calculated gas void fractions for several models were described. The best agreement between the measured and calculated gas void fractions were obtained for strongly dispersed water - oil flow.

6

Designing a simple radiometric system to predict void fraction percentage independent of flow pattern using radial basis function

75%

Roshani Gholam H. , Ehsan N. , Farzin S. , Imani Mohammad A. , Salar M.

|

7

Evaluation of liquid-gas flow in pipeline using gamma-ray absorption technique and advanced signal processing

75%

Hanus R. , Zych M. , Mosorov V. , Golijanek-Jędrzejczyk A. , Jaszczur M. , Andruszkiewicz A. , Hanus R. , Zych M. , Mosorov V. , Golijanek-Jędrzejczyk A. , Jaszczur M. , Andruszkiewicz A.

|

8

Określenie udziału objętościowego metodami stereologicznymi

75%

Masiukiewicz M.

|

2005

|

tom z. 80

103-111

PL

W prezentowanej pracy przedstawiono metodę identyfikacji struktury opartą na analizie obrazu metodami stereologicznymi. Tak opracowany system pomiarowy umożliwia dokonanie oceny zmian struktury mieszaniny dwufazowej zachodzących w czasie na podstawie wybranej grupy stereologicznych parametrów struktury. Cała analiza dokonywana jest na sekwencjach filmowych zarejestrowanych cyfrową kamerą do zdjęć szybkich.

EN

Pattern identification method, based on image analysis with stereological techniques, is presented in this paper. Developed measurement method allows estimation of changes of two phase mixture flow pattern in time. The measurements are taken on selected group of stereological parameters of the pattern. The analysis is done on movie clips of investigated process. Recorded images are taken with the use of high speed CCD camera.

9

Design and simulation of a multienergy gamma ray absorptiometry system for multiphase flow metering with accurate void fraction and water-liquid ratio approximation

63%

Khayat O. , Afarideh H.

Nukleonika

|

2019

|

tom Vol. 64, No. 1

19--29

EN

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.

10

Experimental investigations into the impact of the void fraction on the condensation characteristics of R134a refrigerant in minichannels under conditions of periodic instability

63%

Kuczyński W. , Charun H.

|

2011

|

tom Vol. 32, no. 2

21-37

EN

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.

11

Wpływ ciśnienia na hydrodynamikę przepływu mieszaniny dwufazowej ciecz - gaz w minikanale

63%

Sowiński J. , Fidos H.

|

tom Nr 4

72-73

PL

W pracy zbadano wpływ ciśnienia panującego podczas przepływu mieszanina dwufazowej ciecz - gaz w minikanale na wartości wyznaczanych udziałów faz. Ciśnienia w minikanale zmieniano poprzez zwiększanie ciśnienia hydrostatycznego na jego wylocie. W wyniku przeprowadzonych badań stwierdzono, istotny wpływ wielkości ciśnienia w minikanale na rejestrowane wartości udziału faz oraz na wielkości i kształty przepływających w mieszaninie dwufazowej pęcherzy gazowych.

EN

The aim of this study was to investigate an influence of pressure during flow of two-phase gas - liquid mixture in a mini-channel on values of determined phase fractures. Pressure in the mini-channel was changed by increasing hydrostatic pressure at the outlet. As a result of investigations it was found the significant influence of pressure in the minichannel on recorded values of phase fracture, size and shape of gas bubbles in two-phase mixture.

12

Wpływ wypełnienia porowatego na wymianę ciepła oraz hydrodynamikę przepływu gaz-ciecz przez metale komórkowe

63%

Dyga R. , Witczak S.

|

tom Nr 6

314-315

PL

Przedstawiono analizę wyników badań doświadczalnych dotyczących wymiany cicpla oraz hydrodynamiki przepływu dwufazowego gaz - ciecz przez kanał wypełniony pianą aluminiową. Stwierdzono, że zarówno z punktu widzenia wymiany ciepła jak i hydrodynamiki przepływu, dominującą rolę w przepływie odgrywa ciecz. Zwraca uwagę fakt, że obecność piany aluminiowej nie powoduje rozproszenia płynów, a kształtujące się struktury przepływu odpowiadają strukturom w kanałach niewypełnionych.

EN

Analysis of experimental results dealing with heat exchange and hydrodynamics of two-phase gas-liquid flow through a channel filled with aluminium foam is presented. It was found that from heat transfer and flow hydrodynamics point of view liquid plays predominant role. It is also worth noting that the presence of aluminium foam does not cause fluid dispersion and the formed flow structures correspond to those occurring in unfilled channels.