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1
Content available Badanie mieszania i transportu masy w przepływowym układzie ciecz-ciecz z wykorzystaniem technik CFD
Dzierla J., Staszak M., Alejski K.
Inżynieria i Aparatura Chemiczna
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2018
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Nr 3
57--58
PL
W pracy zbadano transport masy w przepływie segmentowym generowanym w mikroreaktorze typu T. Przebieg reakcji śledzono dzięki zmianie barwy błękitu bromotymolowego podczas neutralizacji wodnego roztworu NaOH za pomocą CH3COOH. Na podstawie analizy zdjęć zaobserwowano niejednolitość w rozkładzie stężeń oraz obecność stref o słabym mieszaniu. Ich obecność potwierdzono za pomocą CFD. Wykazano również zależność między szybkością reakcji a wartością dyssypacji energii.
EN
The work involved the mass transfer in the segmented flow generated in a T-type microreactor. The reaction course was monitored by changing a color of bromothymol blue while neutralizing NaOH with CH3COOH. The heterogeneity in distribution of concentrations and the presence of poor mixing zones were observed during the analysis of photos. The presence of these zones was confirmed usinf CFD techniques. The relationship between the reaction rate and a value of energy dissipation was also shown.
2
Content available remote An analysis and interpretation of the signals in gamma‑absorption measurements of liquid–gas intermittent flow
Zych M.
Acta Geophysica
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2018
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Vol. 66, no. 6
1435--1451
EN
The intermittent flow (slug and plug type) of liquid–gas mixtures in a horizontal pipeline measured by the specific radiometric apparatus is presented. The measurement system consists of two sources of Am-241 gamma radiation and two scintillation probes. An analysis of the signals measured by the radiometric equipment is performed in the domain of time and of frequency. Recognised signal parameters are directly referred to physical quantities associated with a liquid–gas flow. The employed methodology enables determination of gas-phase flow velocity and estimation of the average depth and length of bubble gas structures. In the paper, the processing and interpretation results of the selected experiment are presented to show the in-depth description of gas structures and the type of flows recognition.
3
Content available Algorytm MEB konwekcji wymuszonej w przepływie przez przewody prostoosiowe
Teleszewski T. J.
Symulacja w Badaniach i Rozwoju
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2015
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Vol. 6, nr 3
193--201
PL
W pracy przedstawiono algorytm MEB symulacji konwekcji wymuszonej przy przepływie korkowym przez prostoosiowe przewody o zróżnicowanym kształcie przekroju. Weryfikacja metody elementów brzegowych została wykonana poprzez porównanie rezultatów obliczeń MEB z rozwiązaniem analityczno-empirycznym. W pracy przedstawiono graficzne rezultaty obliczeń symulacji konwekcji wymuszonej w przewodzie o przekroju siedmiokąta foremnego oraz wyznaczono funkcję liczby Nusselta w zależności od liczby ścianek tworzących przekrój przewodu prostoosiowego o kształcie wielokąta foremnego.
EN
The paper presents the numerical algorithm Boundary Element Method to simulation modelling of slug flow in forced convection through straight ducts of arbitrary cross section. The efficiency and the credibility of proposed algorithm were verified by numerical tests in known solution. A numerical examples are presented fully developed forced convection through heptagon duct. In this study is proposed for determining the Nusselt number in regular polygonal channels of slug flow in forced convection.
4
Content available remote Prediction of holdup in liquid slugs
Brauner N., Ullmann A.
Transactions of the Institute of Fluid-Flow Machinery
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2003
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nr 112
75--90
EN
Correlations and models from the literature for the prediction of void fraction in liquid slugs are reviewed. It is shown that a mechanism that can explain the slug aeration in vertical, horizontal and inclined tubes has not yet been established. A new model that attributes the aeration of the liquid slug to a recurrent bubble entrainment from the Taylor bubble (TB) tail is introtuced. The bubble fragmentation is related to the rate of turbulent kinetic energy in the shear layer, which is formed at the TB wake as the liquid film plunges into the slug front. The model has been tested against experimental data available from the literature and was found to predict the effects of liquid and gas flow rates and physical properties, as well as tube diameter and inclination on the void fraction.
5
Content available remote Evolution of flow patterns, gas fraction profiles and bubble size distributions in gas-liquid flows in vertical tubes
Lucas D., Krepper E., Prasser H. M.
Transactions of the Institute of Fluid-Flow Machinery
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2003
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nr 112
37-46
EN
Air-water flow at ambient conditions in a vertical pipe an inner diameter of 51.2 mm is investigated. An electrode wire-mesh sensor enables the measurement of the phase distribution with a very high resolution in space and in time. Local bubble size distributions are calculated from the data. The measurements were done in distances from the gas injection device. As a result, the development of bubble size distributions as well as the development of the radial gas fraction profiles can be studiet. It was found, that the bubble size distribution as well as local effects determine the transistion from bubble flow. The data are used for the development of a model, which predicts the development of the bubble size distribution and the transition from bubble flow in the case of stationary flow in a vertical pipe.
6
Content available remote Pulsating heat pipes: a challenge and still unsolved problem in heat pipe science
Groll M., Khandekar S.
Archives of Thermodynamics
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2002
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Vol. 23, no 4
17-28
EN
Modern micro electronics thermal management is facing considerable challenges in the wake of miniaturizing of components leading to higher demands on net heat flux dissipation. This paper highlights the salient features of Pulsating Heat Pipes (PHPs), a novel research topic in the heat pipe science, having potential applications in thermal management of micro/power electronics. This apparently simple cooling device, is considerably intriguing for theoretical and experimental investigations alike. Fundamental operating principle, flow characteristics, design parameters and limitations are discussed in detail. The unresolved open questions which are subject to further investigations are also outlined.
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