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1

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

Khayat Omid, Afarideh Hossein

Nukleonika

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2019

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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.

2

Utrzymanie reżimu temperaturowego i płukanie instalacji jako działania wspomagające redukcję zanieczyszczenia bakteriami z rodzaju Legionella

Matuszewska R.

Instal

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2016

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nr 12

41--44

PL

Bakterie z rodzaju Legionella są często wykrywane w systemach dystrybucji wody, zwłaszcza w instalacjach ciepłej wody. Występowaniu tych bakterii sprzyjają między innymi: zbyt niska temperatura wody ciepłej, obecność osadu, korozja, biofilm, zastoiny wody. Systematyczna kontrola temperatury wody w punktach kontrolnych (np.: podgrzewacz wody, cyrkulacja, reprezentatywne punkty czerpalne) w systemach dystrybucji wody zimnej i ciepłej w budynkach oraz reżim przepływu wody powinny być stałymi elementami zarządzania instalacjami. Utrzymywanie odpowiedniej temperatury wody ciepłej (> 50°C) i wody zimnej (< 20°C) oraz regularne płukanie pryszniców/kranów powinny być działaniami wspomagającymi procesy dezynfekcji oraz mającymi na celu ograniczenie występowania warunków korzystnych dla bakterii Legionella.

EN

Bacteria of Legionella genus are often detected in domestic water systems, especially in the hot water system. The low temperature of hot water, presence of sludge, corrosion, biofilm and stagnation of water promote the presence of these bacteria. Systematic control of water temperature at control points (f. e.: water heater, circulation, representative points of use) in water distribution systems and flow regime should be a fixed part of domestic water systems management. Maintaining a suitable hightemperature of hot water (> 50°C) and low temperature of cold water (< 20°C) and regular shower / taps flushing should be supportive measures of disinfection process aimed at reducing the occurrence of favorableconditions for Legionella bacteria.

3

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

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

Nukleonika

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2012

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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.

4

Environmental heterogeneity controls organic-matter dynamics in river-floodplain ecosystems

Langhans Simone D., Tiegs Scott D., Uehlinger Urs, Tockner Klement

Polish Journal of Ecology

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2006

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Vol. 54, nr 4

675-680

EN

Environmental heterogeneity is a key regulator of ecological processes. Riverine floodplains are particularly heterogeneous and dynamic systems and loss of their natural environmental heterogeneity and dynamism as a consequence of human impacts constitutes their most serious threat. On river floodplains, flow and flood pulses create a shifting mosaic of channels, ponds, bars, islands, and riparian forest patches. Composition and spatial arrangement of these habitat patches determine their degree of connectivity, which in turn controls the flux of matter and energy among adjacent patches. In light of these attributes, riverine floodplains are model ecosystems for studying the effect of heterogeneity on ecological processes. In this article we introduce a conceptual model for river-floodplain ecosystems that unifies leaf decomposition, organic-matter input, storage and quality, and stresses the importance of the flow and inundation regime. In combining these aspects of organic matter dynamics, which have been treated separately in the ecological literature, this model fosters a more holistic perspective of ecosystem processes on riverine floodplains. We conclude that the linkage between natural heterogeneity and ecosystem processes needs to be considered in future river-floodplain restoration projects.

5

Identification of steam-water two-phase flow regimes in vertical upward tube

Bai B., Guo L., Zhao L.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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1999

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Z. 67

173--183

EN

Both the fluctuating static pressures on the tube wall and the differential pressure fluctuation were measured to obtain the objective identification of steam-water two-phase flow regimes in a vertical upward tube of 20.0-mm interior diameter. The test pressures were 1.0MPa, 2.0MPa and 3.0MPa and the mass flux ranged from 100 to 900kg/m2s. The fluctuating mechanisms were studied by the statistical theory. The root mean square (RMS) of the pressure fluctuation can not be used to discriminate the flow regime transition under the condition of the high pressure, which was used successfully by Wambsganss in air-liquid loop. The frequency of differential pressure fluctuation ranged from 0 to 5 Hertz, and the shapes of the PDF and PSD concerned the various flow regimes. The flow regimes can be identified based on the RMS of the differential pressure fluctuation. The results by the method agreed well with the flow regimes provided by McQuillan and Whalley.