scholarly journals MODELLING OF THE BREAK UP MECHANISM IN GAS ATOMIZATION OF LIQUID METALS

2020 ◽  
Author(s):  
Georgios S.E. Antipas
Keyword(s):  
Gas Phase ◽  
Liquid Metals ◽  
Wave Crest ◽  
Empirical Correlations ◽  
Shape Model ◽  
Liquid Body ◽  
Model Predictions ◽  
Break Up ◽  
Size Distribution Of Particles ◽  
Time Future

An integrated model of the atomization of a liquid column perturbed by a flowing gas phase is proposed. The algorithm termed Surface Wave Formation (SWF) is based on the concept of the formation of sinusoidal waves travelling along the surface of the liquid. The amplitude of such instabilities can grow exponentially under specific conditions, effectively causing the detachment of liquid particles either by shearing of part of a wave crest or by detachment of a liquid body at negative amplitude nodes. The SWF model covers both primary and secondary atomization and can in principle describe the break up of any well defined liquid shape. Model predictions compare favourably with experimental data from close coupled atomization of metals. The implications of the SWF algorithm are important, since - unlike empirical correlations - it can predict the size distribution of particles inside a spray in space and atomization time. Future integration could include calculations of cooling histories of drops in flight.

Gas Phase and Surface Reactions in Mocvd of GaAs from Triethylgallium, Trimethylgallium, and Organometallic Arsenic Precursors

1988 ◽  
Vol 131 ◽  
Author(s):  
Thomas R. Omstead ◽  
Penny M. Van Sickle ◽  
Klavs F. Jensen
Keyword(s):  
Gas Phase ◽  
Low Temperatures ◽  
Surface Reactions ◽  
Rate Data ◽  
Gas Phase Reactions ◽  
Heated Zone ◽  
Model Predictions ◽  
First Time ◽  
Good Agreement

ABSTRACTThe growth of GaAs from triethylgallium (TEG) and trimethylgallium (TMG) with tertiarybutylarsine (tBAs), triethylarsenic (TEAs), and trimethylarsenic (TMAs), has been investigated by using a reactor equipped with a recording microbalance for in situ rate measurements. Rate data show that the growth with these precursors is dominated by the formation of adduct compounds in the gas lines, by adduct related parasitic gas phase reactions in the heated zone, and by the surface reactions. A model is proposed for the competition between deposition reactions and the parasitic gas phase reactions. Model predictions are in very good agreement with experimental data for all combinations of precursors except for TEG/TMAs where extensive gallium droplet formation is observed at low temperatures. Growth of reasonable quality GaAs with Hall mobilities of 7600 cm2/Vs at 77 K using TEG and tBAs is reported for the first time.

Simulation of Multiphase Heat Transfer in Pebble Bed Modular Reactor

2004 ◽  
Author(s):  
Andrey A. Troshko ◽  
Ajey Y. Walavalkar
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Packed Bed ◽  
Multiphase Model ◽  
Test Rig ◽  
Pebble Bed ◽  
Model Predictions ◽  
Two Phases ◽  
Drag Law ◽  
Eulerian Multiphase Model

Computational Fluid Dynamics in conjunction with an Eulerian multiphase model of heat transfer in a Pebble Bed Modular Reactor (PBMR) was validated against experimental data obtained in a test rig. The cooling gas and packed fuel pebbles constituted two phases. The velocity of pebble phase was fixed to zero and a drag law accounting for a packed bed condition was used. The density of the gas phase varied with temperature. Volume averaged effective thermal conductivities accounting for radiation and packed spheres geometry were used for both phases. Model predictions compared favorably with the experiment for two gases — helium and nitrogen and two power levels. It was found that accounting for increased affective porosity close to walls results in more realistic velocity field prediction.

scholarly journals Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US

2018 ◽  
Vol 18 (1) ◽  
pp. 357-370 ◽  
Author(s):  
Havala O. T. Pye ◽  
Andreas Zuend ◽  
Juliane L. Fry ◽  
Gabriel Isaacman-VanWertz ◽  
Shannon L. Capps ◽  
...  
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Thermodynamic Model ◽  
Ambient Air ◽  
Particle Phase ◽  
Organic System ◽  
Pure Species ◽  
Southeastern Us ◽  
Model Predictions ◽  
Total Ammonia

Abstract. Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (ratio of ammonium to 2  ×  sulfate, RN∕2S  ≈  0.8 to 0.9) with approximately 70 % of total ammonia and ammonium (NHx) in the particle. Southeastern Aerosol Research and Characterization Network (SEARCH) gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and Gases in Ambient air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to a factor of 3 overestimate of the nonvolatile cations. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and aerosol mass spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H+]air (H+ in µg m−3 air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid–liquid phase separation. In addition, accounting for nonideal mixing modified the pH such that a fully interactive inorganic–organic system had a pH roughly 0.7 units higher than predicted using traditional methods (pH  =  1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C  ≥  0.6) compounds including several isoprene-derived tracers as well as levoglucosan but decrease particle-phase partitioning for low O : C, monoterpene-derived species.

scholarly journals Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern United States

2017 ◽  
Author(s):  
Havala O. T. Pye ◽  
Andreas Zuend ◽  
Juliane L. Fry ◽  
Gabriel Isaacman-VanWertz ◽  
Shannon L. Capps ◽  
...  
Keyword(s):  
United States ◽  
Gas Phase ◽  
Organic Compounds ◽  
Thermodynamic Model ◽  
Southeastern United States ◽  
Particle Phase ◽  
Organic System ◽  
Pure Species ◽  
Model Predictions ◽  
Total Ammonia

Abstract. Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phase for conditions in the southeastern United States during summer 2013. Existing equilibrium models and frameworks were found to be sufficient although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (Ratio of ammonium to 2 × sulfate, RN/2S ≈ 0.8 to 0.9) with approximately 70 % of total ammonia and ammonium (NHx) in the particle. Southeastern Aerosol Research and Characterization (SEARCH) network gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for Aerosols and Gases in Air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to biases in the nonvolatile cations that resulted from either overestimated emissions and/or underestimated mixing. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and Aerosol Mass Spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H+]air (H+ in μg m−3 air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid-liquid phase separation. In addition, accounting for non-ideal mixing modified the pH such that a fully interactive inorganic-organic system had a pH roughly 0.7 units higher than predicted by traditional methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C ≥ 0.6) compounds including several isoprene-derived tracers as well as levoglucosan, but decrease particle-phase partitioning for low O : C, monoterpene-derived species.

Effect of Solids Loading, Reynolds Number, and Particle Size Distribution on Velocity Fluctuations in Gas-Particle Flows

2003 ◽  
Author(s):  
Jennifer Sinclair Curtis
Keyword(s):  
Reynolds Number ◽  
Gas Phase ◽  
Single Phase ◽  
Glass Beads ◽  
Coarse Particles ◽  
Single Phase Flow ◽  
Velocity Fluctuations ◽  
Flow Models ◽  
Solids Loading ◽  
Model Predictions

A variety of LDV experiments were conducted to assess the influence of solids loading, Reynolds number and particle size distribution on velocity fluctuations and flow behavior in gas-particle systems. This talk will summarize those experimental findings, as well as show comparisons of experimental results with multiphase CFD model predictions that utilize concepts from kinetic theory to describe particle velocity fluctuations. In order to probe solids loading effects, an axisymmetric particle-laden jet was investigated using LDV for 70 micron glass beads with solids loadings ranging from one to thirty. Dilute conditions are characterized by isotropic particle r.m.s. velocities and decreases in the magnitude of the r.m.s. velocities as the solids loading increases. Particle clustering is observed for dense conditions as well as anisotropy between axial and radial particle r.m.s. velocities. Under dense conditions, increases in the solids loading lead to increases in the axial particle r.m.s. velocity while the radial r.m.s. velocity remains at a constant level. Gas-solids flow models display good agreement between predictions and experimental measurements of mean velocities of the gas and solids as well as modulation of the gas turbulent kinetic energy by the presence of the particles. However, the gas-solid flow models based on kinetic theory concepts consistently overpredict the particle r.m.s. velocity for the range of solids loadings investigated. In addition, the same axisymmetric particle-laden jet consisting of 70-micron glass beads was investigated for a range of Reynolds numbers with a constant mass loading (m = 0.7). The presence of the solids dampens the gas turbulence intensity at the lowest value of Re investigated (8,300) compared with single-phase flow at the same Re. As the Reynolds number increases, the gas turbulence increases and for Re ≥ 15,200 the turbulence is enhanced compared with the single-phase flow at the same Re. The observed trend in turbulence modulation with Reynolds number is possibly due to the segregation of the solids and their effect on the gas mean velocity profiles. Finally, the particle-laden jet was investigated for binary mixtures of 25 and 70-micron glass beads. Specifically, the effect of a bimodal PSD on the modulation of gas-phase turbulence, the particle rms velocity, and particle segregation patterns was explored in detail. Measurements and model predictions indicate that increasing the mass fraction of the finer particles dampens the gas-phase turbulence. Changes in the random motion of the coarser particles are observed upon the addition of the finer material; clusters of fine particles arise for the largest solids loading investigated, and these clusters increase both the mean and fluctuating velocities of the coarse particles. The particles are also observed to segregate by size and volume fraction, with the coarse particles tending towards the center of the pipe.

scholarly journals Experimental studies of two-phase liquid metal-gas chain flow with ultrasonic echo pulse method and in the magnetic field of permanent magnets

2018 ◽  
Vol 240 ◽  
pp. 03003
Author(s):  
Artur Andruszkiewicz ◽  
Kerstin Eckert
Keyword(s):  
Magnetic Field ◽  
Gas Phase ◽  
Gas Flow ◽  
Permanent Magnets ◽  
Liquid Metals ◽  
Experimental Studies ◽  
Pulse Method ◽  
Phase Flow ◽  
Ultrasonic Echo ◽  
Echo Pulse

Metallurgical processes of refining and degassing liquid metals are related to the blowing-in neutral gasses like for example argon. Effectiveness of the process depends on the flowing gas parameters like: dimensions, velocity, distribution amd gas phase flow zone. These parameters can be changed under the influence of outside magnetic field and formed by it a Lorentz’ force. In order to get full information of rising bubbles essential are certain measuring methods. Among many of these the ultrasonic echo pulse method is likely to be the most intensive developed in the past few years. That method enables estimation of gas phase flow parameters in a range from individual bubble flow up to full continuous gas flow at the inlet nozzle. In this paper a measurement principle has been described for an ultrasonic echo method and there also submitted and discussed results of obtained results for diphase flow of GaInSn-argon.

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