Wyniki wyszukiwania - BazTech

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Numerical simulation of two-phase gas-liquid flow through horizontal annulus pipe

Nyong Oku E., Igbong Dodeye, Ebieto Celestine, Ene Bassey Ekpo, Oluwadare Benjamin, Eso Archibong Archibong

Archives of Thermodynamics

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2023

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Vol. 44, no 4

705--731

EN

Chemical, petroleum and nuclear systems are only a few of the industrial processes that utilize gas-liquid flow in annular closed channels. However, concentric horizontal annuli flow patterns have received little attention. The ability to precisely characterize two-phase flow patterns using computational techniques is crucial for the production, transportation, and optimization of designs. This current research aims to establish the accuracy of the computational fluid dynamics (CFD) model in predicting the gas-liquid flow pattern in the concentric annulus pipe and validating the flow pattern of liquid holdup with experimental results from the literature. The simulations were done on a test section of a 12.8 m length pipe with a hydraulic diameter of 0.0168 m using air and water as the working fluids. The volume of fluid (VOF) model in Ansys Fluent based on the Eulerian- Eulerian approach in conjunction with the realizable k-ε turbulence model was used to model the gas-liquid flow pattern, i.e. dispersed bubble, elongated bubble, and slug in a horizontal annulus. A comparison of the model with the experimental high-speed video images shows a reasonable agreement for the flow pattern and liquid holdup data.

2

Optimization the operation parameters of SDA desulfurization tower by flow coupling chemical reaction model

Mei Dan, Shi Junjie, Zhu Yuzheng, Xu Xuemei, Xing Futang, Shi Ling

Polish Journal of Chemical Technology

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2020

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Vol. 22, nr 1

35--45

EN

Spray Drying Absorber (SDA) has been widely used for large-scale desulfurization. However, it also has some limitations. For example, the liquid absorbent easily causes scaling, which impedes the contact between the serous fluid and the flue gas and reduces the chemical reaction rate and desulfurization efficiency. This paper establishes the mathematical and physical model of gas and liquid two-phase flow and droplet evaporation and heat transfer in rotary spray desulfurization tower. To study the accumulation and distribution of chemical reaction precipitates in the desulfurization tower and analyze the removal efficiency of sulfur dioxide (SO2) in different atomization diameters, this paper establishes a simulation model concerning the coupling of desulfurization reaction and flow field calculation based on the absorption and reaction mechanism of SO2. Baffle in different widths are set to optimize the internal floweld and balance the distribution of flue gas. By setting baffles of different widths to optimize the flow feld in the tower and changing the distribution of flue gas, this model reduces the scaling while ensuring the desulfurization efficiency. The results of the simulation experiment have verified that the droplet with a diameter of 50 μm is the optimal option, which can effectively remove the scaling and ensure that the desulfurizing tower runs in high efficiency and stability. When the width of baffes is 2250 mm, the efficiency of desulfurization exceeds 95%, and the amount of scaling on the desulfurization tower main wall is controlled at the minimum level, which is the optimal option for production.

3

New gas-liquid two-phase flow pattern maps based on the energy ratio of pressure fluctuation through a Venturi tube

Sun Zhiqiang, Chen Luyang, Yao Fengyan

Metrology and Measurement Systems

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2019

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Vol. 26, nr 2

241--252

EN

To find effective and practical methods to distinguish gas-liquid two-phase flow patterns, new flow pattern maps are established using the differential pressure through a classical Venturi tube. The differential pressure signal was first decomposed adaptively into a series of intrinsic mode functions (IMFs) by the ensemble empirical mode decomposition. Hilbert marginal spectra of the IMFs showed that the flow patterns are related to the amplitude of the pressure fluctuation. The cross-correlation method was employed to sift the characteristic IMF, and then the energy ratio of the characteristic IMF to the raw signal was proposed to construct flow pattern maps with the volumetric void fraction and with the two-phase Reynolds number, respectively. The identification rates of these two maps are verified to be 91.18% and 92.65%. This approach provides a cost-effective solution to the difficult problem of identifying gas-liquid flow patterns in the industrial field.

4

Zastosowanie tomografii obrazowej do pomiaru parametrów poruszających się pęcherzyków gazu - algorytm rekonstrukcji

Rząsa M.R.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 9a

116-120

PL

W pracy przedstawiono ideę nowatorskiej metody pomiarowej opartej na tomografii obrazowej. Idea metody polega na zarejestrowaniu obrazu poruszających się pęcherzyków z dwóch prostopadłych kierunków. Na podstawie dwóch obrazów jest wyznaczany środek masy, trajektoria ruchu, prędkości lokalne oraz poprzez przybliżenie kształtu pęcherzyków znanymi figurami geometrycznymi możliwe jest określenie jego objętości i powierzchni. W pracy szczegółowo opisano algorytm rekonstrukcji kształtu i trajektorii ruchu pęcherzyków.

EN

The paper presents a new measuring method based on graphic tomography. The method insists in registration of the image of bubbles moving from two perpendicular directions. Two images are applied for determination of the center of mass, the movement trajectory, local velocities. Approximation of the bubble shape with the known geometric figures allows to determine its volume and surface. In the paper, the algorithm of reconstruction of a shape and a movement trajectory of the bubbles is discussed.

5

Determination of interfacial parameters of horizontal two-phase plug flow using a high speed pulse-echo ultrasonic technique

Masala T., Harvel G., Su J., Chang J.

Transactions of the Institute of Fluid-Flow Machinery

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2010

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nr 122

61-76

EN

This paper presents a high-speed, multiple-transducers, pulse-echo ultrasonic technique for the measurement of interfacial parameters of horizontal two-phase intermittent flow regimes. The ultrasonic system consisted of an ultrasonic driver, a multiplexer with 4 transducers, and a microcomputer equipped with a data acquisition card, a motion controller card and the Winspect Data Acquisition software. Two transducers were mounted on the top of a 2.1 cm inner diameter circular pipe, while the other two transducers were mounted on the bottom of the pipe. Using instantaneous liquid level measurements from multiple transducers, two-phase flow interfacial parameters in plug were determined, such as the lengths and the velocities of liquid plugs and bubbles, the shape of the gas-liquid interface, and hence instantaneous and cross sectional averaged void fraction and interfacial area. The results showed that the liquid plug velocities as well as the elongated bubble velocity increases with increasing superficial liquid and gas velocities. An experimental correlation for liquid plug velocity was proposed based on the present results. The results also showed that the time and cross-sectional averaged void fraction in the plug flow regime was only slightly influenced by the superficial gas velocity but was not influenced by the superficial liquid velocity.

6

Identyfikacja struktur przy przepływie gaz - ciecz w wymienniku ciepła o niewielkich rozmiarach z wykorzystaniem cyfrowej anemometrii obrazowej DPIV

Karaś M., Zając D., Ulbrich R.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 3

43-44

PL

Zjawisko przepływu gaz ciecz wokół pęku rur występuje w wielu procesach przemysłowych. W tej pracy przedstawiono przegląd najnowszych badań przepływu dwufazowego wokół pęku rur wykonanych techniką cyfrowej anemometrii obrazowej DPIV z wykorzystaniem kamer o dużej prędkości rejestracji obrazu w wysokiej rozdzielczości. Przedstawiono również wyniki badań własnych przepływu dwufazowego powietrze — woda w modelu płaszczowo rurowego wymiennika ciepła.

EN

Two phase flow around a tube bundle exist in many industrial processes. The newest researches of two-phase flow around the tube bundle using the DPIV measuring method and high speed cameras are described in this paper. The experimental setup and measurements of air - water flow in the heat exchanger model are presented. Complexity of two-phase flow is shown using velocity fields and stream lines.