Number of found documents: 550
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Deposition limit velocity: effect of particle size distribution
Matoušek, Václav; Visintainer, R.; Furlan, J.; McCall II, G.; Sellgren, A.
2017 - English
Industrial settling slurries often consist of particles of very different sizes; the particle size distribution may cover sizes which differ with two orders of magnitude. A broad particle size distribution affects parameters of slurry flow including deposition limit velocity. We present experimental results of the deposition limit velocity collected during a comprehensive experimental campaign testing slurry flows composed of solids of different fractions in the GIW Hydraulic Laboratory in 2016. Four narrow graded fractions (carrier fluid, pseudo-homogeneous, heterogeneous, and stratified) were tested in permutations from the individual components to the complete mixture at various concentrations. The primary experiments were carried out in a 203-mm pipe, and selected corresponding experiments were repeated in a 103-mm pipe. The experimental results show that interactions among components affect the resulting deposition limit velocity in flows of broadly graded settling slurries. The effect of particle size distribution on the deposition limit velocity is not benign. The deposit velocity is not necessarily lower in a flow of slurry composed of four components than in slurry flow of one component with the highest deposit velocity from the four components. We discuss possible modifications of a deposit velocity predictive model in order to take effects of a broad particle size distribution into account. Keywords: settling slurry flow; deposit in pipe; four component model; mixture flow experiment Available at various institutes of the ASCR
Deposition limit velocity: effect of particle size distribution

Industrial settling slurries often consist of particles of very different sizes; the particle size distribution may cover sizes which differ with two orders of magnitude. A broad particle size ...

Matoušek, Václav; Visintainer, R.; Furlan, J.; McCall II, G.; Sellgren, A.
Ústav pro hydrodynamiku, 2017

The role of sonication of polyethyleneoxide solutions containing magnetic nanoparticles on morphology of nanofibrous mats
Peer, Petra; Stěnička, M.; Filip, Petr; Pizúrová, Naděžda; Babayan, V.
2017 - English
Properties of the resulting polymer nanofibers are often tailored by sonication technique applied prior or past\nan electrospinning process. The aim of this contribution is to evaluate morphology of nanofibrous mats formed\nby poly(ethylene oxide) with distributed magnetic nanoparticles (MNP) (about 20 nm in diameter) in\ndependence on time of sonication of the used polymer solutions. The solutions were exposed to sonication\n(intensity 200W, frequency 24 kHz) for 10, 30, and 60 minutes. It was shown that rheological characteristics\n(viscosity, storage and loss moduli) strongly depend on time of sonication (particularly phase angle) in contrast\nto electric conductivity and surface tension. For analysis of homogeneous distribution of MNP in polymer\nsolution, the rheological measurements were carried out also in presence of external magnetic field.\nMagnetorheological efficiency (a relation of corresponding viscosities) was determined for 80, 170, and 255\nmT. Consequently, changed rheological characteristics participate significantly in the process of\nelectrospinning and resulting quality of the obtained nanofibrous mats. Qualitative changes were described by\nmeans of scanning electron microscopy (variance of mean diameter of nanofibers), transmission electron\nmicroscopy (distribution of MNP within nanofibrous mats). Static magnetic properties were determined by a\nvibration sample magnetometer. It was shown that even distribution of MNP in the mats can be achieved by\nmere sonication process without application of external magnetic field during an electrospinning process.\nHowever, time of sonication generates a degree of embedding of MNP into individual nanofibers. Keywords: ultrasound; poly(ethylene oxide); magnetic nanoparticles; magnetorheology; electrospinning Available on request at various institutes of the ASCR
The role of sonication of polyethyleneoxide solutions containing magnetic nanoparticles on morphology of nanofibrous mats

Properties of the resulting polymer nanofibers are often tailored by sonication technique applied prior or past\nan electrospinning process. The aim of this contribution is to evaluate morphology of ...

Peer, Petra; Stěnička, M.; Filip, Petr; Pizúrová, Naděžda; Babayan, V.
Ústav pro hydrodynamiku, 2017

Concentration distribution and slip velocity of coarse-particle-water mixture in horizontal and inclined pipe sections
Vlasák, Pavel; Chára, Zdeněk; Konfršt, Jiří
2017 - English
Narrow particle size distribution basalt pebbles of mean particle size 11.5 mm conveyed by water in the pipe sections of different inclination were investigated on an experimental pipe loop of inner diameter D = 100 mm. Mixture flow-behaviour and the concentration distribution were studied in a pipe viewing section and with the application of a gamma-ray densitometer. The study refers to the effect of mixture velocity, overall concentration, and angle of pipe inclination on chord-averaged concentration profiles and local concentration maps. The study revealed that the coarse particle-water mixtures in the inclined pipe sections were significantly stratified, the solid particles moved principally close to the pipe invert, and for higher and moderate flow velocities particle saltation becomes the dominant mode of particle conveying. Keywords: hydraulic conveying; concentration distribution; pipe inclination; Gamma-Ray radiometry; mixture flow behaviour Available on request at various institutes of the ASCR
Concentration distribution and slip velocity of coarse-particle-water mixture in horizontal and inclined pipe sections

Narrow particle size distribution basalt pebbles of mean particle size 11.5 mm conveyed by water in the pipe sections of different inclination were investigated on an experimental pipe loop of inner ...

Vlasák, Pavel; Chára, Zdeněk; Konfršt, Jiří
Ústav pro hydrodynamiku, 2017

Měření velikosti kapek ve dvoufázovém systému
Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Kotek, M.; Šulc, R.
2017 - Czech
Available at various institutes of the ASCR
Měření velikosti kapek ve dvoufázovém systému

Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Kotek, M.; Šulc, R.
Ústav pro hydrodynamiku, 2017

Flow of heterogeneous slurry in horizontal and inclined pipes
Vlasák, Pavel; Chára, Zdeněk; Konfršt, Jiří; Kysela, Bohuš
2017 - English
Narrow particle size distribution heterogeneous slurries were investigated on an experimental pipe loop with the horizontal and inclined pipe sections of inner diameter 100 mm. The investigation was focused on the effect of the pipe inclination, average slurry velocity and overall concentration and on the local concentration distribution, pressure drop, deposition limit and carrier liquid-particle slip velocity. The local concentration distribution was studied with the application of a gamma-ray densitometer. Mixture flow-behaviour and particles motion were investigated in a pipe viewing section. The study revealed that the heterogeneous slurries in the horizontal and inclined pipe sections were significantly stratified, the solid particles moved principally close to the pipe invert, and particle saltation becomes the dominant mode of particle conveying for higher and moderate flow velocities. Carrier liquid-particle slip velocity depends not only on the mixture velocity, but also on particle position in the pipe cross-section. The effect of pipe inclination on the frictional pressure drop in inclined pipe sections depends on mixture velocity, in ascending pipe section decreases with increasing mixture velocity and in descending pipe section the frictional pressure drop gradually decreased with increasing pipe inclination. Keywords: solid-liquid mixture; pipe inclination; slip velocity; mixture flow behaviour; concentration distribution Available at various institutes of the ASCR
Flow of heterogeneous slurry in horizontal and inclined pipes

Narrow particle size distribution heterogeneous slurries were investigated on an experimental pipe loop with the horizontal and inclined pipe sections of inner diameter 100 mm. The investigation was ...

Vlasák, Pavel; Chára, Zdeněk; Konfršt, Jiří; Kysela, Bohuš
Ústav pro hydrodynamiku, 2017

Chlorečnan jako jeden z vedlejších produktů desinfekce vody Chlornanem sodným
Drdová, Š.; Parschová, H.; Pivokonský, Martin; Janda, V.
2016 - Czech
Příspěvek je zaměřen na problematiku chlorečnanů, které vznikají jako vedlejší produkt desinfekce vody za využití chlornanu sodného. Pozornost byla věnována zejména době a způsobu skladování roztoku chlornanu sodného s ohledem na tvorbu chlorečnanů i dalších vedlejších produktů. The study deals with the formation of chlorate as a disinfection by-product when using sodium hypochlorite. The relationship between aging and storing conditions of sodium hypochlorite and the production of chlorite and other DBPs was investigated. Keywords: chlorate; DBPs (Disinfection By-Products); sodium hypochlorite; sodium hypochlorite Available on request at various institutes of the ASCR
Chlorečnan jako jeden z vedlejších produktů desinfekce vody Chlornanem sodným

Příspěvek je zaměřen na problematiku chlorečnanů, které vznikají jako vedlejší produkt desinfekce vody za využití chlornanu sodného. Pozornost byla věnována zejména době a způsobu skladování roztoku ...

Drdová, Š.; Parschová, H.; Pivokonský, Martin; Janda, V.
Ústav pro hydrodynamiku, 2016

Discharged stream from radial impeller, comparison of LDA and PIV measurements
Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Jašíková, D.; Němcová, L.; Kopecký, V.
2016 - Czech
Míchání je v procesní technice velice důležitá operace, která má za úkol vytvořit homogenní\nsměs, homogenní suspenzi, lépe rozdružit materiál v disperzích, atp. Míchaná nádoba je\naparát, kde má docházet k energeticky co nejpříznivějšímu míchání různých látek. V této\npráci se zaměřujeme na míchané nádoby s tzv. radiálním rychloběžným míchadlem.\nModelování velkých nádob na základě experimentů na malých nádobách je prováděno\npomocí podobnostních přepočtů. Základní parametry přepočtů lze analyzovat především na\nzákladě znalostí proudového pole v míchaném objemu, případně dalších veličin, jejichž\nvýsledky jsou stále předmětem ověřování a zpřesňování.\nV této práci jsme se zaměřili na měření rychlostního pole na výtoku z tzv. Rushtonova\nturbínového míchadla [1,2,3], kde vytékající proud z lopatek bývá popisován analogicky jako\ntok v zatopeném proudu [4]. Rychlostní profily byly měřeny pomocí dvousložkového LDA\nměření (radiální a tangenciální složka). Třetí (axiální) složka byla měřena následně po\npřestavění měřícího LDA systému. Získaná data časových záznamů byla podrobena další\nanalýze při vyhodnocování statistických veličin časově středních hodnot rychlostí a velikosti\nfluktuačních složek. Two velocity measurement methods in discharged stream from Rushton turbine are compared. The tested methods are LDA (Laser Doppler Anemometry) and stereo TR PIV (Time Resolved Particle Image Velocimetry). The discrepancy of evaluated data from stereo PIV affected by transforming recalculation in discharged stream is presented. Keywords: mixing vessel; Rushton turbine; LDA; PIV Available at various institutes of the ASCR
Discharged stream from radial impeller, comparison of LDA and PIV measurements

Míchání je v procesní technice velice důležitá operace, která má za úkol vytvořit homogenní\nsměs, homogenní suspenzi, lépe rozdružit materiál v disperzích, atp. Míchaná nádoba je\naparát, kde má ...

Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Jašíková, D.; Němcová, L.; Kopecký, V.
Ústav pro hydrodynamiku, 2016

Sezónní proměnlivost parametrů půdních modelů
Šípek, Václav; Tesař, Miroslav
2016 - Czech
Simulace nasycení půdního profilu v malém horském povodí a testování dvou sezónních setů parametrů. Simulation of saturation of the soil profile in the small mountain river basins and testing of two seasonal sets of parameters. Keywords: soil moisture; seasonal variability; saturated hydraulic conductivity; poresize distribution; hydrological modelling; soil hydraulic parameters Available in digital repository of the ASCR
Sezónní proměnlivost parametrů půdních modelů

Simulace nasycení půdního profilu v malém horském povodí a testování dvou sezónních setů parametrů....

Šípek, Václav; Tesař, Miroslav
Ústav pro hydrodynamiku, 2016

Permeation of VOC vapours through carbon nanotube network membranes controlled electrically
Slobodian, P.; Říha, Pavel; Olejník, R.
2016 - English
In this letter, we report the increase of permeation rates of some typical volatile organic compounds through entangled carbon nanotube networks by an electric current. The change in the permeation rate is reversible when the\ncurrent is turned off. The permeation rise is partly probably due to Joule effect and thus increased membrane temperature and vapor pressure in the vicinity of the inlet side of membrane. However, the effects of vapor polarity and electrostatic interaction of vapors and charged nanotubes seem to be also involved and contribute to the differentiation between alcohol and carbohydrate vapors permeation. Keywords: electroconductive polymer mebranes; vapor permeation; electrical stimulation Available on request at various institutes of the ASCR
Permeation of VOC vapours through carbon nanotube network membranes controlled electrically

In this letter, we report the increase of permeation rates of some typical volatile organic compounds through entangled carbon nanotube networks by an electric current. The change in the permeation ...

Slobodian, P.; Říha, Pavel; Olejník, R.
Ústav pro hydrodynamiku, 2016

30th Symposium on Anemometry: proceedings
Chára, Zdeněk; Klaboch, L.
2016 -
Sborník z konference 30th symposium o anemometrii. Konference byla zaměřena na experimentální techniky používané v mechanice tekutin.\n Proceedings of 30th Symposium on Anemometry. The conference was oriented on the experimental techniques applied in fluid mechanics. Keywords: anemometry; conference; turbulence Available at various institutes of the ASCR
30th Symposium on Anemometry: proceedings

Sborník z konference 30th symposium o anemometrii. Konference byla zaměřena na experimentální techniky používané v mechanice tekutin.\n...

Chára, Zdeněk; Klaboch, L.
Ústav pro hydrodynamiku, 2016

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