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Статті в журналах з теми "H-bubbles"
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Occhionero, Franco, Luca Amendola, and Pier Stefano Corasaniti. "Primordial Bubbles within Primordial Bubbles." Symposium - International Astronomical Union 201 (2005): 497–98. http://dx.doi.org/10.1017/s0074180900216847.
Повний текст джерелаАнотація:
Two consecutive, distinct episodes of phase transition occurring during inflation may nucleate two generations of bubbles, one inside the other. We design a model of inflation that realizes this sequence and yields bubble spectra that are bimodal and tunable functions of phenomelogical parameters in turn combinations of microphysical parameters. We argue in favor of a tuning of the parameters such that the outer and earlier generation of bubbles becomes hundreds of Mpc/h in diameter (like the local Hubble bubbles of the literature) whereas the inner and later generation becomes tens of Mpc/h in diameter (like the observed large scale voids).
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Li, G., B. Ning, L. Liu, W. Wan, and J. Y. Liu. "Effect of magnetic activity on plasma bubbles over equatorial and low-latitude regions in East Asia." Annales Geophysicae 27, no. 1 (January 19, 2009): 303–12. http://dx.doi.org/10.5194/angeo-27-303-2009.
Повний текст джерелаАнотація:
Abstract. The dependence of plasma bubble occurrence in the eveningside ionosphere, with magnetic activity during the period years 2001–2004, is studied here based on the TEC observations gathered by ground-based GPS receivers which are located in the equatorial and low-latitude regions in East Asia. The observed plasma bubbles consist of the plasma-bubble events in the equatorial (stations GUAM, PIMO and KAYT), and low-latitude regions (stations WUHN, DAEJ and SHAO). It is shown that most equatorial plasma-bubble events commence at 20:00 LT, and may last for >60 min. The magnetic activity appears to suppress the generation of equatorial plasma bubbles with a time delay of more than 3 h (4–9 h). While in the low-latitude regions, most plasma-bubble events commence at about 23:00 LT and last for <45 min. The best correlation between Kp and low-latitude plasma-bubble occurrence is found with an 8–9 h delay, a weak correlation exists for time delays of 6–7 h. This probably indicates that over 3 h delayed disturbance dynamo electric fields obviously inhibit the development of plasma bubbles in the pre-midnight sector.
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Randsoe, Thomas, and Ole Hyldegaard. "Effect of oxygen breathing on micro oxygen bubbles in nitrogen-depleted rat adipose tissue at sea level and 25 kPa altitude exposures." Journal of Applied Physiology 113, no. 3 (August 1, 2012): 426–33. http://dx.doi.org/10.1152/japplphysiol.00193.2012.
Повний текст джерелаАнотація:
The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently until they disappeared from view at a net disappearance rate (0.02 mm2 × min−1) significantly faster than for similar bubbles at 25 kPa altitude (0.01 mm2 × min−1). At 25 kPa, most bubbles initially grew for 2–40 min, after which they shrank and disappeared. Four bubbles did not disappear while at 25 kPa. The results support bubble kinetic models based on Fick's first law of diffusion, Boyles law, and the oxygen window effect, predicting that oxygen contributes more to bubble volume and growth during hypobaric conditions. As the effect of oxygen increases, the lower the ambient pressure. The results indicate that recompression is instrumental in the treatment of aDCS.
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Palmeirim, P., A. Zavagno, D. Elia, T. J. T. Moore, A. Whitworth, P. Tremblin, A. Traficante, et al. "Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane." Astronomy & Astrophysics 605 (September 2017): A35. http://dx.doi.org/10.1051/0004-6361/201629963.
Повний текст джерелаАнотація:
We present a comprehensive statistical analysis of star-forming objects located in the vicinities of 1360 bubble structures throughout the Galactic plane and their local environments. The compilation of ~70 000 star-forming sources, found in the proximity of the ionized (Hii) regions and detected in both Hi-GAL and GLIMPSE surveys, provided a broad overview of the different evolutionary stages of star-formation in bubbles, from prestellar objects to more evolved young stellar objects (YSOs). Surface density maps of star-forming objects clearly reveal an evolutionary trend where more evolved star-forming objects (Class II YSO candidates) are found spatially located near the center, while younger star-forming objects are found at the edge of the bubbles. We derived dynamic ages for a subsample of 182 H ii regions for which kinematic distances and radio continuum flux measurements were available. We detect approximately 80% more star-forming sources per unit area in the direction of bubbles than in the surrounding fields. We estimate the clump formation efficiency (CFE) of Hi-GAL clumps in the direction of the shell of the bubbles to be ~15%, around twice the value of the CFE in fields that are not affected by feedback effects. We find that the higher values of CFE are mostly due to the higher CFE of protostellar clumps, in particular in younger bubbles, whose density of the bubble shells is higher. We argue that the formation rate from prestellar to protostellar phase is probably higher during the early stages of the (H ii ) bubble expansion. Furthermore, we also find a higher fraction of massive YSOs (MYSOs) in bubbles at the early stages of expansion (<2 Myr) than older bubbles. Evaluation of the fragmentation time inside the shell of bubbles advocates the preexistence of clumps in the medium before the bubble expansion in order to explain the formation of MYSOs in the youngest H ii regions (<1 Myr), as supported by numerical simulations. Approximately 23% of the Hi-GAL clumps are found located in the direction of a bubble, with 15% for prestellar clumps and 41% for protostellar clumps. We argue that the high fraction of protostellar clumps may be due to the acceleration of the star-formation process cause by the feedback of the (Hii) bubbles.
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Hou, L. G., and X. Y. Gao. "Radio recombination line observations towards Spitzer infrared bubbles with the TianMa radio telescope." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 5, 2019): 4862–74. http://dx.doi.org/10.1093/mnras/stz2466.
Повний текст джерелаАнотація:
ABSTRACT Many of the Spitzer infrared bubbles identified by the Milky Way Project (MWP) are suggested to be $\rm{H \small {II}} $ regions in nature. More than 70 per cent of the ∼5000 known bubbles do not have radio recombination line (RRL) observations, hence have not been confirmed as $\rm{H \small {II}} $ regions. A systematic RRL survey should be helpful to identify the nature of the bubbles. With the Shanghai TianMa 65-m radio telescope, we searched for RRLs towards 216 selected Spitzer bubbles by simultaneously observing 19 RRLs in the C band (4–8 GHz). RRLs are detected in the directions of 75 of the 216 targets. 31 of the 75 RRL sources are classified as new detections, which are possibly from new $\rm{H \small {II}} $ regions or diffuse warm ionized medium; 36 of them are probably from the outskirts of nearby bright $\rm{H \small {II}} $ regions, rather than bubble-encircled ionized gas; and the detected RRLs towards 8 bubbles are identified from known $\rm{H \small {II}} $ regions. For 58 of the 75 RRL sources, we obtained their distances after resolving the kinematic distance ambiguity by combining the results of the H2CO absorption method, the $\rm{H \small {I}} $ emission/absorption method, and the $\rm{H \small {I}} $ self-absorption method. The low detection rate of new $\rm{H \small {II}} $ regions implies that a number of MWP bubbles in the DR1 catalogue are too faint if they are $\rm{H \small {II}} $ regions.
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Song, Yan Yan, Guo Qi Liu, Hong Xia Li, and Wen Gang Yang. "Influence of Ladle Purging Plug Airway on Flow Properties of Liquid Steel." Advanced Materials Research 472-475 (February 2012): 2581–87. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.2581.
Повний текст джерелаАнотація:
The influence of the different airway structure on mixing time of molten steel are studied through using water model experiments. The bubble volume and velocity have been investigated through the PIV for different airway structure in the flow of 1m3/h. Results showed that with the slit distribution same, the smaller the slit width, the greater the volume percentage of the large bubbles and the average velocity of the bubbles in rising, but the shorter the mixing time. Reduce the number of the slit can lead to the volume percentage of the large bubbles and the average velocity of the bubbles in rising decreases, the mixing time extended, and it is more obvious to the mixing time to reduce the number of the inner slit. Inflatable volume<1.1m3/h, with the slit in the outer ring only and the number of slit same, the volume percentage and the average velocity of the large bubbles in rising is larger, the mixing time is reduced. Inflatable volume≥1.1m3/h, the slit evenly distribution is better for mixing.
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Randsøe, T., T. M. Kvist, and O. Hyldegaard. "Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures." Journal of Applied Physiology 105, no. 5 (November 2008): 1492–97. http://dx.doi.org/10.1152/japplphysiol.90840.2008.
Повний текст джерелаАнотація:
At altitude, bubbles are known to form and grow in blood and tissues causing altitude decompression sickness. Previous reports indicate that treatment of decompression sickness by means of oxygen breathing at altitude may cause unwanted bubble growth. In this report we visually followed the in vivo changes of micro air bubbles injected into adipose tissue of anesthetized rats at 101.3 kPa (sea level) after which they were decompressed from 101.3 kPa to and held at 25 kPa (10,350 m), during breathing of oxygen or a heliox(34:66) mixture (34% helium and 66% oxygen). Furthermore, bubbles were studied during oxygen breathing preceded by a 3-h period of preoxygenation to eliminate tissue nitrogen before decompression. During oxygen breathing, bubbles grew from 11 to 198 min (mean: 121 min, ±SD 53.4) after which they remained stable or began to shrink slowly. During heliox breathing bubbles grew from 30 to 130 min (mean: 67 min, ±SD 31.0) from which point they stabilized or shrank slowly. No bubbles disappeared during either oxygen or heliox breathing. Preoxygenation followed by continuous oxygen breathing at altitude caused most bubbles to grow from 19 to 179 min (mean: 51 min, ±SD 47.7) after which they started shrinking or remained stable throughout the observation period. Bubble growth time was significantly longer during oxygen breathing compared with heliox breathing and preoxygenated animals. Significantly more bubbles disappeared in preoxygenated animals compared with oxygen and heliox breathing. Preoxygenation enhanced bubble disappearance compared with oxygen and heliox breathing but did not prevent bubble growth. The results indicate that oxygen breathing at 25 kPa promotes air bubble growth in adipose tissue regardless of the tissue nitrogen pressure.
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Wang, Ziyue, Liansheng Liu, Runze Duan, and Liang Tian. "The aerobreakup of bubbles in continuous airflow." Physics of Fluids 34, no. 4 (April 2022): 043317. http://dx.doi.org/10.1063/5.0086604.
Повний текст джерелаАнотація:
Floating soap bubbles usually break up owing to gravitational drainage, surface evaporation, environmental disturbances, and collisions with objects. If a gust of wind blows into a bubble, does the bubble break, and, if so, how does it do so? This study reports experiments that use a high-speed camera to examine the dynamic behaviors of a suspended bubble that is suddenly exposed to continuous airflow. Specifically, the behaviors and mechanisms of the aerobreakup of bubbles are explored. The suspended bubble undergoes shedding and deformation under aerodynamic force and flows with airflow. As the Weber number ( We) increases, the parameter of Taylor deformation ( DT) first increases and then decreases. At a higher Reynolds number, K–H waves appear on the surface of the film owing to the strong shear of airflow on the liquid film. Most such bubbles break due to the shear of the wake vortices on the leeward surface or surface waves on the windward surface, both of which are shearing. The aerobreakup of the bubbles becomes more severe with an increase in We, and they successively exhibit modes of wind-flowing, leeward breakup, windward breakup, and multihole breakup.
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CALDIROLI, PAOLO, and ROBERTA MUSINA. "EXISTENCE OF MINIMAL H-BUBBLES." Communications in Contemporary Mathematics 04, no. 02 (May 2002): 177–209. http://dx.doi.org/10.1142/s021919970200066x.
Повний текст джерелаАнотація:
Given a function H ∈ C1 (ℝ3) asymptotic to a constant at infinity, we investigate the existence of H-bubbles, i.e., nontrivial, conformal surfaces parametrized by the sphere, with mean curvature H. Under some global hypotheses we prove the existence of H-bubbles with minimal energy.
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Ohiomoba, Emmanuel, Ayokunle Omosebi, Gao Xin, and Kunlei Liu. "(Invited) Elucidating the Hydrodynamic Behavior of Multi-Species Gas Bubbles in an Electrochemical Solvent Regenerator for Direct Air Capture." ECS Meeting Abstracts MA2022-02, no. 27 (October 9, 2022): 1036. http://dx.doi.org/10.1149/ma2022-02271036mtgabs.
Повний текст джерелаАнотація:
Direct Air Capture (DAC) is very significant to bolstering the global drive towards net negative emissions. DAC technologies/plants have emerged in recent years, with the regeneration of the capture solvent used in the process being the major bottleneck of most aqueous technologies. [1] Leveraging electrochemical principles has offered a potential opportunity to simplify the entire solvent regeneration process and potentially reduce its overall capture cost, compared to traditional approaches. The electrochemical approach also offers the benefit of direct integrating clean energy, and also eliminating the high thermal energy requirements of typical methods.[2] Despite these potentials, the complex three-phase (solid-liquid-gas) interaction on the electrode surface pose a significant impediment to this electrochemical approach for DAC. The evolution of gas bubbles in electrochemical cells are well-known to contribute to energy losses in such reactors, from previous studies. [3],[4],[5] Gas bubbles have been shown to influence ohmic overpotentials in electrochemical reactors and studies have shown that the energy demand for water electrolysis can be reduced by 10-25 percent if the formation of gas bubbles is suppressed. [6],[7] However, the evolution of gas bubbles in electrochemical systems remains a complicated issue requiring further investigation. This study advances previous work by investigating the simultaneous evolution of CO2 gas bubbles along with O2/H2 gas bubbles in an electrochemical reactor for DAC. Gas bubbles are infamous for their ability to cover the active area of electrodes, limiting the transport of reactive species to the electrode surface, thus, increasing cell resistance. In this work, we explore changes in the polarization and hydrodynamics behavior of gas bubbles in the electrolyzer used for DAC solvent regeneration owing to the evolution of CO2 bubbles from pH swing, and the implications of the additional CO2 bubble formation to electrode surface coverage. By using a high-speed camera, we observe that bubbles coverage appears to be larger at the edges of the electrodes, and that the orientation of the electrodes influence bubble coalescence and detachment rate. We also employ different cell designs to mitigate the impact of bubble surface coverage towards reducing cell resistance. References Sabatino, A. Grimm, F. Gallucci, M. Van Sint Annaland, G. J. Kramer, M. Gazzani, Joule, 5(8), 2047-2076 (2021). Gao, A. Omosebi, R. Perrone, K. Liu, Journal of The Electrochemical Society (2022). H. Li, Y. J. Chen, Scientific Reports, 11(1), 1-12 (2021). F. Swiegers, R. N. L.Terrett, G. Tsekouras, T. Tsuzuki, R. J. Pace, R. Stranger, Sustainable Energy & Fuels, 5(11), 3004–3004 (2021). Zhao, H. Ren, L. Luo, Langmuir, 35(16), 5392-5408 (2019). Mazloomi, N. B. Sulaiman, H. Moayedi, International Journal of Electrochemical Science, 7(4), 3314-3326 (2012). C. Wang, C. Y. Chen, Electrochimica Acta, 54(15), 3877-3883 (2009).
Дисертації з теми "H-bubbles"
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Acher, Thomas [Verfasser], Wolfgang H. [Akademischer Betreuer] Polifke, and Kai-Olaf [Akademischer Betreuer] Hinrichsen. "A Moments Model for the Numerical Simulation of Bubble Column Flows / Thomas Acher. Gutachter: Wolfgang H. Polifke ; Kai-Olaf Hinrichsen. Betreuer: Wolfgang H. Polifke." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1069986135/34.
Повний текст джерелаЧастини книг з теми "H-bubbles"
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Aulerich, Nicole M., Scott H. Irwin, and Philip Garcia. "6. Bubbles, Food Prices, and Speculation: Evidence from the CFTC’s Daily Large Trader Data Files - Nicole M. Aulerich, Scott H. Irwin, and Philip Garcia, Comment." In The Economics of Food Price Volatility, 211–60. University of Chicago Press, 2014. http://dx.doi.org/10.7208/chicago/9780226129082.003.0007.
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"FIG. 26 Effect of bubble size on the dimensionless plots of (z −z)/H." In Surface and Interfacial Tension, 79. CRC Press, 2004. http://dx.doi.org/10.1201/9780203021262-23.
Повний текст джерелаТези доповідей конференцій з теми "H-bubbles"
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Liu, Hong-bo, and Liang-ming Pan. "The Effect of Electromagnetic Field on the Behavior of Bubbles." In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-15689.
Повний текст джерелаАнотація:
The coalescence and motion behaviors of bubbles can be influenced by electromagnetic field, it can be found in the TOKAMK fusion reactors of ITER program. In this paper, VOF (Volume of Fluid) method is adopt to simulate the single bubble rising behavior and bubble coalescence in stagnant liquid under the electromagnetic field within a cylinder closure (D = 20mm, H = 50mm). A three-dimensional numerical simulation is presented considering the driving effect of uniform electric field and magnetic field on the process of bubble rising and bubbles inline coalescence in stagnant liquid pool. The interesting local Magneto-hydrodynamic (MHD) flow, which is produced due to current non-homogenous distribution around the insolated gas bubble, is discussed in the process of single bubble rising and coalescence of bubbles inline. Under the influence of local MHD flow, the rising bubble shape presents obvious deformation. More importantly, as the existence of rotating Lorentz force, the liquid film between two bubbles is stirred, the process of coalescence is largely accelerated.
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Seki, Hiroki, Keisuke Fujita, Toshiyuki Ogasawara, and Hiroyuki Takahira. "Numerical Simulations of Growth and Collapse of a Bubble Between Two Parallel Walls." In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-05175.
Повний текст джерелаАнотація:
In liquid mercury target systems for high-intense pulsed-spallation neutron sources, the material damage of the vessel wall caused by the cavitation bubble collapse is an important issue to be overcome. One remedy is to install a narrow channel for mercury flows. In such a situation, it is important to clarify the dynamics of the growth and collapse of bubbles in a narrow channel and to predict the damage of the channel walls by the bubble collapse. In the present study, therefore, the growth and collapse of bubbles between two parallel walls are investigated by using two kinds of numerical methods: one is the boundary element method (BEM) and the other is the ghost fluid method (GFM). Main concern in the present study is the bubble dynamics when the equilibrium bubble diameter at its maximum volume, deq=2Req, is larger than the channel height between two walls, h; in this case, the bubble shape is not spherical when it grows between two walls. The present results show that the bubble shape at the maximum volume is much dependent on η=h/Req). In the case of η=1.57, the bubble becomes an ellipsoidal shape at its maximum volume, and when η=0.94, the bubble becomes a flattened hourglass shape. When the ellipsoidal bubble collapses, the bubble splits into two parts leading to the liquid jet impact on nearer walls. On the other hand, the bubble with the flattened hourglass shape collapses neutrally at the middle of the walls without translational motion of its main body. The impulsive pressure on the wall observed in the neutral collapse is lower than that in the case of the splitting bubble.
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Billette, Stuart C., and Philip L. Marston. "Scattering of light by a coated bubble in water near the critical scattering angle." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.fr3.
Повний текст джерелаАнотація:
Microbubbles in the ocean may be coated by a thin film of surfactant since such substances can be abundant in natural waters. We investigated theoretical scattering patterns for a spherical gas bubble (of radius a) coated by a film of uniform thickness h and refractive index n f surrounded by water of refractive index n w = 4/3. The patterns were computed from the partial-wave series of Aden and Kerker for ka ranging from 100 to 2500 where 2π/k is the optical wavelength in water. The corresponding range of a is 7.5 to 189 μm; h ranged from 0 to 3 μm and n f was typically real and equal to 1.5. Noncoated bubbles are known1 to exhibit coarse irradiance oscillations as the scattering angle θ decreases below a critical value for total reflection θ C = 82.8°. Anticipated coatings remove neither this coarse structure nor the superimposed finely spaced structure. The magnitude of the latter can be enhanced by the coating. The coarse oscillations are perceivably shifted toward larger θ when n f > n w . Ray optics predicts a shift in θ C ∝ (n f − n w )h/a when h≪ a and |n f − n w | ≪ n w − 1. When using the irradiance near 82.8° to size bubbles, this shift in θ c is negligible for anticipated coating parameters.
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Liu, Jiang-Tao, Yong Tian, and Xiao-Feng Peng. "Bubble Characteristics During Boiling in Microchannels." In ASME 3rd International Conference on Microchannels and Minichannels. ASMEDC, 2005. http://dx.doi.org/10.1115/icmm2005-75163.
Повний текст джерелаАнотація:
A series of visualized experiments were conducted to investigate the boiling nucleation and bubble dynamics restricted within parallel microchannels on a silicon chip. The cross-section of each channel was 100 μm (W) × 100 μm (H). A high-speed CCD camera (up to 8,000 fps) was employed together with a microscope to record the boiling process. Under the present experimental conditions, the incipience of boiling was captured. The rates of bubble growth were measured at various flow and heating conditions. The interaction between vapor bubbles, vapor-liquid interface, and solid wall, was analyzed.
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Krueger, Paul S., Razvan Bidoae, and Peter E. Raad. "Simulation of Air Entrapment by a Plunging Liquid Jet of Finite Length." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56291.
Повний текст джерелаАнотація:
The impingement of a finite length round water jet on a large pool of water was simulated numerically using a 3D Eulerian-Lagrangian Marker and Micro-Cell (ELMMC) method. The method allowed simulation of the initial impact of the jet on the pool surface, the deformation of the pool surface by the falling jet, and, under certain conditions, the entrapment of an air bubble as the pool closes in on the jet. The conditions considered were for ratios of jet length to radius (h/r) in the range of 4 to 25 and jet Froude number in the range of 16 to 74. The results agreed with previous experimental observations by Oguz et al. (J. Fluid Mech., 294, 1995) in terms of entrapped air volume and the possible geometries of entrapped bubbles (viz., toroidal or spheroidal). The simulation results also allowed for a detailed study of effects difficult to discern experimentally, such as vorticity generation and differences in entrapped air volume between toroidal and spheroidal bubbles.
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Knauer, Oliver S., Andreas Braeuer, Matthias C. Lang, and Alfred Leipertz. "Measurement of Concentration and Temperature Gradients at Binary Mixture Boiling Bubbles." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22054.
Повний текст джерелаАнотація:
Due to the high heat flux available, nucleate boiling is one of the most utilized processes for the transfer of large amounts of heat in chemical or power engineering applications. Nevertheless, the basic physical phenomena of this kind of heat transfer are physically not well understood, especially for multi-component mixtures in which the heat transfer coefficient is a function of the mixture composition. To apprehend the binary mixture boiling phenomena, the knowledge of the composition and temperature field surrounding a boiling bubble near the heater surface is of great impact. These quantities are measured at individual boiling bubbles by means of laser-optical methods without disturbing the system and with high spatial resolution. An optical accessible and temperature adjustable boiling chamber for the generation of single bubbles of acetone-isopropanol mixtures was constructed. As the vapor-liquid equilibriums (VLE) of these mixtures show a large gap between the saturated liquid and vapor line, significant composition alterations occur during the phase transition. Concentration and temperature gradients have been measured along a line by linear Raman spectroscopy. Due to the species specific Raman shift and the linear superposition of the inelastic scattered light intensities, qualitative and quantitative composition information can be achieved. In alcohols, e.g. isopropanol, the molecules can develop hydrogen bonds, which have an impact on the shape of the O-H bind signal in the Raman spectrum. As the ratio of molecules with and without hydrogen bonds changes with temperature, the temperature of the liquid phase can be derived from the spectra as well. The results show an enhancement of isopropanol, the less volatile component, near the phase boundary due to preferential evaporation of acetone. Furthermore, a not expected depletion of isopropanol approximately 0.75 mm away from the bubble was measured. The detected temperature increases near the boiling bubble, indicating a heat transfer from the gas phase to the surrounding liquid. The temperature distribution also has a minimum at the same position as the isopropanol distribution. A species conservation calculation with simplified assumptions was carried out and validated the measured composition distribution in the liquid surrounding a boiling bubble.
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Povich, Matt. "Beyond Strömgren Spheres and Wind-Blown Bubbles: An Observational Perspective on H II Region Feedback." In Frank N. Bash Symposium 2011: New Horizons in Astronomy. Trieste, Italy: Sissa Medialab, 2012. http://dx.doi.org/10.22323/1.149.0006.
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Li, Yun, and Huiying Wu. "An Experimental Investigation of Flow Boiling Characteristics in Interconnected Microchannels With Different Slot Arrangement." In ASME 2022 Heat Transfer Summer Conference collocated with the ASME 2022 16th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/ht2022-81624.
Повний текст джерелаАнотація:
Abstract Flow boiling in microchannels is a promising approach to solve the heat dissipation problems of the electronic components. In this work, two types of interconnected slot microchannels (SM) with the staggered (SSM) and in-line (ISM) arrangement of the slots (W = 300μm, H = 600μm) are fabricated. Flow boiling experiments are conducted in the SMs (W = 300μm, H = 600μm, L = 35mm) at mass fluxes of 118–370 kg/m2·s, with the deionized water being used as the working fluid. It is found that compared with plain-wall microchannels (PM), the critical heat fluxes (CHF) in ISM are increased by 24.3%∼50.0%, and 30.8∼53.1% for SSM within the test range. The comparative study with PM reveals that SMs can significantly promote the bubbly flow. Equally important, IMs increase the effective heat transfer area while facilitating the redevelopment of the liquid film. Therefore, the heat transfer coefficient (HTC) in ISM and SSM are significantly enhanced by 44.8% ∼ 60.9% and 43.7% ∼ 68.3%, respectively. Furthermore, the connection of the microchannels promotes the mixing of the fluid and enables a more uniform flow distribution in microchannels. The interconnected slots provide the lateral expansion space for bubbles, thus suppressing the reversal flow of the bubbles. Compared with ISM, SSM could break out the long slug bubbles more effectively and prevent gigantic bubbles from forming. The two-phase pressure drop in SSM could be reduced by 23% on average compared with ISM. This work is trying to provide an improved design for microchannels to enhance the flow boiling process.
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McAuliffe, B. R., and M. I. Yaras. "Numerical Study of Instability Mechanisms Leading to Transition in Separation Bubbles." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-91018.
Повний текст джерелаАнотація:
In this paper, transition in a separation bubble is examined through numerical simulation. The flow Reynolds number and streamwise pressure distribution are typical of the conditions encountered on the suction side of low-pressure turbine blades of gas-turbine engines. The spatial and temporal resolutions utilized in the present computations correspond to a coarse direct numerical simulation, wherein the majority of turbulence scales, including the inertial subrange, are adequately resolved. The accuracy of the simulation results is demonstrated through favorable comparisons with experimental data corresponding to the same flow conditions. The results of the simulation show linear Tollmien-Schlichting (T-S) instability growth downstream of the point of separation, leading to the roll-up of spanwise vorticity into disctete vortical structures, characteristic of Kelvin-Helmholtz (K-H) instability growth. The extent of cross-stream momentum exchange associated with packets of amplified T-S waves is examined, along with details of the time-periodic breakdown into turbulence occurring upon the development of the K-H instability. Reynolds-averaged properties of the separation bubble are presented, and provide evidence of the strong three-dimensional nature of the reattachment process.
10
Mele´ndez, Elva, and Rene´ Reyes. "Experimental Description of the Convective Heat Transfer Coefficient for Pool Boiling of Binary Mixtures on Porous Heating Surfaces." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47196.
Повний текст джерелаАнотація:
This work presents the experimental results of the effect of porous heating surfaces, and the Marangoni effect on the convective heat transfer coefficient for pool boiling, h. The porous heating surfaces fabricated for these experiments, and the interfacial tension gradients in the binary mixtures reduced the bubbles’ size and their coalescence in the proximity of the heating surface. The convective heat transfer coefficient was calculated for the boiling of pure water and three aqueous mixtures with 12, 16, and 20% weight of ethanol on five different porous coverings on the heating element. Some combinations of these variables were studied in a 32 factorial design, and represented by the response surface calculated. The maximum h for boiling of pure water on the bare surface of the heating element was 50 kW/m2 °C. Using the porous coverings, the maximum h value was 180 kW/m2 °C. For boiling the binary mixtures on the smooth heating element surface the maximum h value was 65 kW/m2 °C, while on the porous coverings the values of h attained a maximum of 220 kW/m2 °C. The maximum values of h correspond to the composition of 16% ethanol, and a porous covering with the smallest porous diameter.
Звіти організацій з теми "H-bubbles"
1
Sartain, Bradley, Kurt Getsinger, Damian Walter, John Madsen, and Shayne Levoy. Flowering rush control in hydrodynamic systems : part 1 : water exchange processes. Engineer Research and Development Center (U.S.), September 2022. http://dx.doi.org/10.21079/11681/45425.
Повний текст джерелаАнотація:
In 2018, field trials evaluated water-exchange processes using rhodamine WT dye to provide guidance on the effective management of flowering rush (Butomus umbellatus L.) at McNary Dam and Reservoir (Wallula Lake, 15,700 ha). Additional evaluations determined the effectiveness of BubbleTubing (hereafter referred to as bubble curtain) at reducing water exchange within potential flowering rush treatment areas. Dye readings were collected from multiple sampling points at specific time intervals until a dye half-life could be determined. Whole-plot dye half-lives at sites without bubble curtain ranged 0.56–6.7 h. In slower water-exchange sites (≥2.6 h dye half-life), the herbicide diquat should have a sufficient contact time to significantly reduce flowering rush aboveground biomass. Other sites demonstrated very rapid water exchange (<1.5 h dye half-life), likely too rapid to effectively control flowering rush using chemical treatments without the use of a barrier or curtain to slow water exchange. At one site, the use of the bubble curtain increased the dye half-life from 3.8 h with no curtain to 7.6 and 7.1 h with a bubble curtain. The bubble curtain’s ability to slow water exchange will provide improved chemical control and in-crease the potential for other chemical products to be effectively used.
2
Lahav, Ori, Albert Heber, and David Broday. Elimination of emissions of ammonia and hydrogen sulfide from confined animal and feeding operations (CAFO) using an adsorption/liquid-redox process with biological regeneration. United States Department of Agriculture, March 2008. http://dx.doi.org/10.32747/2008.7695589.bard.
Повний текст джерелаАнотація:
The project was originally aimed at investigating and developing new efficient methods for cost effective removal of ammonia (NH₃) and hydrogen sulfide (H₂S) from Concentrated Animal Feeding Operations (CAFO), in particular broiler and laying houses (NH₃) and hog houses (H₂S). In both cases, the principal idea was to design and operate a dedicated air collection system that would be used for the treatment of the gases, and that would work independently from the general ventilation system. The advantages envisaged: (1) if collected at a point close to the source of generation, pollutants would arrive at the treatment system at higher concentrations; (2) the air in the vicinity of the animals would be cleaner, a fact that would promote animal growth rates; and (3) collection efficiency would be improved and adverse environmental impact reduced. For practical reasons, the project was divided in two: one effort concentrated on NH₃₍g₎ removal from chicken houses and another on H₂S₍g₎ removal from hog houses. NH₃₍g₎ removal: a novel approach was developed to reduce ammonia emissions from CAFOs in general, and poultry houses in particular. Air sucked by the dedicated air capturing system from close to the litter was shown to have NH₃₍g₎ concentrations an order of magnitude higher than at the vents of the ventilation system. The NH₃₍g₎ rich waste air was conveyed to an acidic (0<pH<~5) bubble column reactor where NH₃ was converted to NH₄⁺. The reactor operated in batch mode, starting at pH 0 and was switched to a new acidic absorption solution just before NH₃₍g₎ breakthrough occurred, at pH ~5. Experiments with a wide range of NH₃₍g₎ concentrations showed that the absorption efficiency was practically 100% throughout the process as long as the face velocity was below 4 cm/s. The potential advantages of the method include high absorption efficiency, lower NH₃₍g₎ concentrations in the vicinity of the birds, generation of a valuable product and the separation between the ventilation and ammonia treatment systems. A small scale pilot operation conducted for 5 weeks in a broiler house showed the approach to be technically feasible. H₂S₍g₎ removal: The main goal of this part was to develop a specific treatment process for minimizing H₂S₍g₎ emissions from hog houses. The proposed process consists of three units: In the 1ˢᵗ H₂S₍g₎ is absorbed into an acidic (pH<2) ferric iron solution and oxidized by Fe(III) to S⁰ in a bubble column reactor. In parallel, Fe(III) is reduced to Fe(II). In the 2ⁿᵈ unit Fe(II) is bio-oxidized back to Fe(III) by Acidithiobacillus ferrooxidans (AF).In the 3ʳᵈ unit S⁰ is separated from solution in a gravity settler. The work focused on three sub-processes: the kinetics of H₂S absorption into a ferric solution at low pH, the kinetics of Fe²⁺ oxidation by AF and the factors that affect ferric iron precipitation (a main obstacle for a continuous operation of the process) under the operational conditions. H₂S removal efficiency was found higher at a higher Fe(III) concentration and also higher for higher H₂S₍g₎ concentrations and lower flow rates of the treated air. The rate limiting step of the H₂S reactive absorption was found to be the chemical reaction rather than the transition from gas to liquid phase. H₂S₍g₎ removal efficiency of >95% was recorded with Fe(III) concentration of 9 g/L using typical AFO air compositions. The 2ⁿᵈ part of the work focused on kinetics of Fe(II) oxidation by AF. A new lab technique was developed for determining the kinetic equation and kinetic parameters (KS, Kₚ and mₘₐₓ) for the bacteria. The 3ʳᵈ part focused on iron oxide precipitation under the operational conditions. It was found that at lower pH (1.5) jarosite accumulation is slower and that the performance of the AF at this pH was sufficient for successive operation of the proposed process at the H₂S fluxes predicted from AFOs. A laboratory-scale test was carried out at Purdue University on the use of the integrated system for simultaneous hydrogen sulfide removal from a H₂S bubble column filled with ferric sulfate solution and biological regeneration of ferric ions in a packed column immobilized with enriched AFbacteria. Results demonstrated the technical feasibility of the integrated system for H₂S removal and simultaneous biological regeneration of Fe(III) for potential continuous treatment of H₂S released from CAFO. NH₃ and H₂S gradient measurements at egg layer and swine barns were conducted in winter and summer at Purdue. Results showed high potential to concentrate NH₃ and H₂S in hog buildings, and NH₃ in layer houses. H₂S emissions from layer houses were too low for a significant gradient. An NH₃ capturing system was designed and tested in a 100-chicken broiler room. Five bell-type collecting devices were installed over the litter to collect NH₃ emissions. While the air extraction system moved only 10% of the total room ventilation airflow rate, the fraction of total ammonia removed was 18%, because of the higher concentration air taken from near the litter. The system demonstrated the potential to reduce emissions from broiler facilities and to concentrate the NH₃ effluent for use in an emission control system. In summary, the project laid a solid foundation for the implementation of both processes, and also resulted in a significant scientific contribution related to AF kinetic studies and ferrous analytical measurements.