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- 저자 : Aliyu, Aliyu Musa (검색결과 54 건)
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Upward gas–liquid two-phase flow after a U-bend in a large-diameter serpentine pipe
Aliyu, Aliyu M.,Almabrok, Almabrok A.,Baba, Yahaya D.,Lao, Liyun,Yeung, Hoi,Kim, Kyung Chun Elsevier 2017 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.108 No.1
<P><B>Abstract</B></P> <P>We present an experimental study on the flow behaviour of gas and liquid in the upward section of a vertical pipe system with an internal diameter of 101.6mm and a serpentine geometry. The experimental matrix consists of superficial gas and liquid velocities in ranges of 0.15–30m/s and from 0.07 to 1.5m/s, respectively, which cover bubbly to annular flow. The effects on the flow behaviours downstream of the 180° return bend are significantly reduced when the flow reaches an axial distance of 47 pipe diameters from the U-bend. Therefore, reasonably developed flow is attained at this development length downstream of the bend. Other published measurements for large-diameter film thickness show similar trends with respect to the superficial gas velocity. However, the trends differ from those of small-diameter pipes, with which the film thickness decreases much faster with increasing gas flow. As a result, only a few of the published correlations for small pipe data agreed with the experimental data for large pipe film thickness. We therefore modified one of the best-performing correlations, which produced a better fit. Qualitative and statistical analyses show that the new correlation provides improved predictions for two-phase flow film thickness in large-diameter pipes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gas–liquid flow experiments performed in a large diameter serpentine flow loop. </LI> <LI> Flow visualisation done using a wire mesh sensor to identify upward flow regimes. </LI> <LI> Conductance probes were used to measure film thickness in the annular regime. </LI> <LI> Asymmetrical films after a U-bend became symmetrical at middle and top positions. </LI> <LI> Improved film thickness correlation was developed and compared with existing ones. </LI> </UL> </P>
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Geochemistry and Petrogenesis of Pan-african Granitoids in Kaiama, North Central, Nigeria
Aliyu Ohiani Umaru(Aliyu Ohiani Umaru ),Olugbenga Okunlola(Olugbenga Okunlola ),Umaru Adamu Danbatta(Umaru Adamu Danbatta ),Olusegun G. Olisa(Olusegun G. Olisa ) 대한자원환경지질학회 2023 자원환경지질 Vol.56 No.3
Pan African granitoids of Kaiama is comprised of K-feldspar rich granites, porphyritic granites, and granitic gneiss that are intruded by quartz veins and aplitic veins and dykes which trend NE-SW. In order to establish the geochemical signatures, petrogenesis, and tectonic settings of the lithological units, petrological, petrographical, and geochemical studies was carried out. Petrographic analysis reveals that the granitoids are dominantly composed of quartz, plagioclase feldspar, biotite, and k-feldspar with occasional muscovites, sericite, and opaque minerals that constitute very low proportion. Major, trace, and rare earth elements geochemical data reveal that the rocks have moderate to high silica (SiO2=63-79.7%) and alumina (Al2O3=11.85-16.15) contents that correlate with the abundance of quartz, feldspars, and biotite. The rocks are calc-alkaline, peraluminous (ASI=1.0-<1.2), and S-type granitoids sourced by melting of pre-existing metasedimentary or sedimentary rocks containing Al, Na, and K oxides. They plot dominantly in the WPG and VAG fields suggesting emplacement in a post-collisional tectonic setting. On a multi-element variation diagram, the granitoids show depletion in Ba, K, P, Rb, and Ti while enrichment was observed for Th, U, Nd, Pb and Sm. Their rare-earth elements pattern is characterized by moderate fractionation ((La/Yb)N=0.52-38.24) and pronounced negative Eu-anomaly (Eu/Eu*=0.02-1.22) that points to the preservation of plagioclase from the source magma. Generally, the geochemical features of the granitoids show that they were derived by the partial melting of crustal rocks with some input from greywacke and pelitic materials in a typical post-collisional tectonic setting.
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Interfacial friction in upward annular gas–liquid two-phase flow in pipes
Aliyu, Aliyu Musa,Baba, Yahaya Danjuma,Lao, Liyun,Yeung, Hoi,Kim, Kyung Chun Elsevier 2017 Experimental thermal and fluid science Vol.84 No.-
<P><B>Abstract</B></P> <P>Accurate prediction of interfacial friction between the gas and liquid in annular two-phase flow in pipes is essential for the proper modelling of pressure drop and heat transfer coefficient in pipeline systems. Many empirical relationships have been obtained over the last half century. However, they are restricted to limited superficial liquid and gas velocity ranges, essentially apply to atmospheric pressures, and the relationships are only relevant for pipes with inner diameters between 10 and 50mm. In this study, we carried out experiments in a large diameter flow loop of 101.6mm internal diameter with the superficial gas and liquid ranges of 11–29m/s and 0.1–1.0m/s respectively. An examination of published interfacial friction factor correlations was carried out using a diverse database which was collected from the open literature for vertical annular flow. The database includes measurements in pipes of 16–127mm inner diameter for the liquid film thickness, interfacial shear stress, and pressure gradient for air-water, air-water/glycerol, and argon-water flows. Eleven studies are represented with experimental pressures of up to 6bar. Significant discrepancies were found between many of the published correlations and the large pipe data, primarily in the thick film region at low interfacial shear stress. A correlation for the interfacial friction factor was hence derived using the extensive database. The correlation includes dimensionless numbers for the effect of the diameter across pipe scales to be better represented and better fit the wide range of experimental conditions, fluid properties, and operating pressures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gas–liquid two-phase flow experiments conducted in a large diameter flow loop. </LI> <LI> Data were collected for interfacial friction factor in upwards annular flow regimes. </LI> <LI> Data were also gathered from other sources spanning both small and large diameter pipes. </LI> <LI> Previous correlations’ predictions deviated at high shear regions mainly for large pipes. </LI> <LI> Improved correlation is proposed to fit the diverse database of more than 300 data points. </LI> </UL> </P>
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Characteristics of bubble-induced liquid flows in a rectangular tank
Aliyu, Aliyu M.,Seo, Hyunduk,Kim, Hyogeun,Kim, Kyung Chun Elsevier 2018 Experimental thermal and fluid science Vol.97 No.-
<P><B>Abstract</B></P> <P>Bubbly flows are frequently encountered in many industrial applications where multiphase contact is used to promote heat, mass and momentum transfer. These include applications where both chemical and physical processes occur, such as wastewater treatment and biological aeration systems. We investigated the behaviour of underwater-generated bubble swarms, which were produced at the bottom of a 1-m<SUP>3</SUP> square tank from a 5-mm nozzle and allowed to rise by buoyancy in still water. Instantaneous velocity fields around the bubbles were obtained using Particle Image Velocimetry (PIV) seeded with 10–15-µm poly-dispersed fluorescent particles and gas flow rates ranging from 2 to 15 L/min (1.7–12.8 m/s). A continuous laser was used to obtain the time-resolved field, and a pulse laser was used to obtain the mean velocity fields. Images were captured at up to 2000 fps. After interrogation, a post-processing validation algorithm was employed to identify and remove vectors produced by bubbles and the interface, essentially producing vector fields of the liquid phase only. Proper orthogonal decomposition analysis was carried out on 1000 realisations of each gas flow case to identify dominant flow structures, and the flow was decomposed into its constituent spatial and temporal modes. We established that induced vortices in the liquid phase more clearly manifest at far streamwise locations shown by the spatial mode at lower gas flow rates and are clearer in the temporal mode at high gas flow rates. The mean streamwise and spanwise liquid velocities increased with the gas flow rate, and the streamwise bubble velocities can be well described by a top-hat profile curve. Finally, an analysis was done to estimate the bubble entrainment coefficient using the slip velocity and the gas buoyancy flux.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We investigated the behaviour of underwater-generated bubble swarms. </LI> <LI> Instantaneous velocity fields around the bubbles were obtained using PIV. </LI> <LI> POD analysis was carried out to identify dominant flow structures. </LI> <LI> The streamwise velocities can be well described by a top-hat profile. </LI> <LI> Bubble entrainment coefficient was estimated using the slip velocity and the gas void fraction. </LI> </UL> </P>
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Prediction of entrained droplet fraction in co-current annular gas-liquid flow in vertical pipes
Aliyu, A.M.,Almabrok, A.A.,Baba, Y.D.,Archibong, A.E.,Lao, L.,Yeung, H.,Kim, K.C. Elsevier 2017 Experimental thermal and fluid science Vol.85 No.-
<P>The entrained droplet fraction is an important parameter in annular two-phase flow, as its correlations are key inputs in flow simulation codes for the prediction of pressure drop and critical heat flux or dryout. Investigators have stressed the importance of extending the validity range of current correlations so that more conditions are covered. This could be achieved for example by including fluids with higher viscosities, a wider range of operating pressures, and increase in the size of pipes used for experiments (most of the data in the literature are from pipes of 50 mm diameter and below). In attempt to improve the latter, experiments were conducted in a 101.6 mm gas liquid flow loop at Cranfield University's Oil and Gas Engineering Laboratory and data on the fraction of droplets were collected in the annular flow regime by measuring the film velocity, from which the droplet fraction was calculated. Comparison of the film velocity by this method and by a mass balance showed close agreement. A capacitance Wire Mesh Sensor was used for flow visualisation in order to distinguish between annular and churn flow. In order to arrive at an improved correlation, over 1300 data points were gathered from other published works. These include air water studies where large pipes of up to 127 mm in diameter were used. The others were from small-diameter pipes and for refrigerant, steam water, air water, and air glycerine flows. Since in the annular regime, the gas flow entrains liquid droplets into the core, their presence alters the properties of the gas core. Therefore, accurate predictions are pivotal for the energy efficient design and operation of facilities in the petroleum and nuclear power industry. The correlation obtained here showed good agreement with the collected databank. (C) 2017 Elsevier Inc. All rights reserved.</P>
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Aliyu, A.M.,Kim, Y.K.,Choi, S.H.,Ahn, J.H.,Kim, K.C. Butterworth ; Elsevier Science Ltd 2017 Flow measurement and instrumentation Vol.56 No.-
A dual-channel optical fiber probe was developed to quantify the bubble characteristics (void fraction, velocity, and bubble size) in a gas-liquid annular ejector system. Water is pumped upstream of the ejector contraction. Since a low pressure region exists downstream in the ejector diffuser, this permits air to be sucked into the flowing liquid by jet pump action and the inlet air volumetric flow rate is measured by a flow meter. Verification of the void fraction (range 0.15-0.5) measured by the optical fiber probe was then possible and deviations were generally around +/- 5%. Also, bubble velocity was measured using the optical probe by cross-correlating signals from the two fibers whose tips are separated by a known distance. Alternatively measuring bubble velocity using a particle image velocimetry method provided validation for the optical fiber probe system where a high speed camera was used to capture instantaneous bubble images at time intervals of 0.125ms. Excellent agreement between the velocities using both methods is reported. For bubble size measurements, analyzing the temporal signals from a single probe enabled estimation of the size of a bubble. Bubble sizes measured ranged between 1.5 and 6.0mm and size distributions were constructed for different ejector water volumetric flow rates ranging from 0.0022 to 0.0063m<SUP>3</SUP>/s. LabVIEW provided a convenient platform for coding the algorithms for estimating the void fraction, bubble velocity and bubble size. For further comparison, a CFD study of the ejector system was done, and the vertical radial profiles of the void fraction were compared with those obtained by the optical fiber system and these showed good agreement.
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