Dynamics of bubble formation at micro-orifices under constant gas flow conditions

2020 ◽  
Vol 132 ◽  
pp. 103407
Author(s):  
Ehsan Mohseni ◽  
Jaunty Jose Kalayathine ◽  
Sebastian Felix Reinecke ◽  
Uwe Hampel
Keyword(s):  
Gas Flow ◽  
Bubble Formation ◽  
Flow Conditions

Bubble formation from sub-millimeter orifices under variable gas flow conditions

2021 ◽  
pp. 116698
Author(s):  
E. Mohseni ◽  
T. Ziegenhein ◽  
S.F. Reinecke ◽  
U. Hampel
Keyword(s):  
Gas Flow ◽  
Bubble Formation ◽  
Flow Conditions

scholarly journals A Mechanistic Model for Bubble Formation from Microscale Orifices under Constant Gas Flow Conditions

2021 ◽  
Author(s):  
Ehsan Mohseni ◽  
Gusttav Bauermann Lang ◽  
Sebastian Felix Reinecke ◽  
Uwe Hampel
Keyword(s):  
Gas Flow ◽  
Mechanistic Model ◽  
Bubble Formation ◽  
Flow Conditions

scholarly journals Experimental Study of Bubble Formation from a Micro-Tube in Non-Newtonian Fluid

Micromachines ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 71
Author(s):  
Georgia Kontaxi ◽  
Yorgos G. Stergiou ◽  
Aikaterini A. Mouza
Keyword(s):  
Liquid Phase ◽  
Shear Rate ◽  
Newtonian Fluid ◽  
Gas Flow ◽  
Bubble Formation ◽  
Release Time ◽  
Internal Diameter ◽  
Asymptotic Value ◽  
Shear Thinning Fluids ◽  
A Value

Over the last few years, microbubbles have found application in biomedicine. In this study, the characteristics of bubbles formed when air is introduced from a micro-tube (internal diameter 110 μm) in non-Newtonian shear thinning fluids are studied. The dependence of the release time and the size of the bubbles on the gas phase rate and liquid phase properties is investigated. The geometrical characteristics of the bubbles are also compared with those formed in Newtonian fluids with similar physical properties. It was found that the final diameter of the bubbles increases by increasing the gas flow rate and the liquid phase viscosity. It was observed that the bubbles formed in a non-Newtonian fluid have practically the same characteristics as those formed in a Newtonian fluid, whose viscosity equals the asymptotic viscosity of the non-Newtonian fluid, leading to the assumption that the shear rate around an under-formation bubble is high, and the viscosity tends to its asymptotic value. To verify this notion, bubble formation was simulated using Computational Fluid Dynamics (CFD). The simulation results revealed that around an under-formation bubble, the shear rate attains a value high enough to lead the viscosity of the non-Newtonian fluid to its asymptotic value.

Diabatic Nozzle Flow with Constant Small Stage Efficiency

1960 ◽  
Vol 64 (598) ◽  
pp. 632-635 ◽  
Author(s):  
R. A. A. Bryant
Keyword(s):  
Gas Flow ◽  
Nozzle Flow ◽  
Flow Conditions ◽  
One Dimensional ◽  
Real Flow ◽  
Stage Efficiency ◽  
Frictional Effects

The concept of small stage efficiency is introduced when studying one-dimensional gas flow in nozzles in order to permit a closer approximation of real flow conditions than is possible from an isentropic analysis. It is more or less conventional to assume the flow conditions are adiabatic whenever the small stage efficiency is used. That is to say, small stage efficiency is generally considered in relation to flows contained within adiabatic boundaries, in which case it becomes a measure of the heat generated by internal frictional effects alone.

scholarly journals Improved Catalytic Transfer Hydrogenation of Levulinate Esters with Alcohols over ZrO2 Catalyst

2020 ◽  
Vol 2 (1) ◽  
pp. 28
Author(s):  
Tommaso Tabanelli ◽  
Paola Blair Vásquez ◽  
Emilia Paone ◽  
Rosario Pietropaolo ◽  
Nikolaos Dimitratos ◽  
...  
Keyword(s):  
Gas Flow ◽  
Agricultural Waste ◽  
High Surface ◽  
High Surface Area ◽  
Tetragonal Zirconia ◽  
Transfer Hydrogenation ◽  
Catalytic Transfer Hydrogenation ◽  
Flow Conditions ◽  
Catalytic Transfer ◽  
Alkyl Levulinates

Levulinic acid (LA) and its esters (alkyl levulinates) are polyfunctional molecules that can be obtained from lignocellulosic biomass. Herein, the catalytic conversion of methyl and ethyl levulinates into γ-valerolactone (GVL) via catalytic transfer hydrogenation (CTH) by using methanol, ethanol, and 2-propanol as the H-donor/solvent, was investigated under both batch and gas-flow conditions. In particular, high-surface-area, tetragonal zirconia has proven to be a suitable catalyst for this reaction. Isopropanol was found to be the best H-donor under batch conditions, with ethyl levulinate providing the highest yield in GVL. However, long reaction times and high autogenic pressures are needed in order to work in the liquid-phase at high temperature with light alcohols. The reactions occurring under continuous gas-flow conditions, at atmospheric pressure and a relatively low contact time (1 s), were found to be much more efficient, also showing excellent GVL yields when EtOH was used as the reducing agent (GVL yield of around 70% under optimized conditions). The reaction has also been tested using a true bio-ethanol, derived from agricultural waste. These results represent the very first examples of the CTH of alkyl levulinates under continuous gas-flow conditions reported in the literature.

Ozone Cracking and Protection of Rubber

1970 ◽  
Vol 43 (5) ◽  
pp. 1230-1254 ◽  
Author(s):  
G. J. Lake
Keyword(s):  
Ozone Concentration ◽  
Test Piece ◽  
Gas Flow ◽  
Protective Layer ◽  
Diffusion Control ◽  
Direct Reaction ◽  
Flow Conditions ◽  
Single Crack ◽  
Layer Development ◽  
Very High

Abstract Studies of the growth of single ozone cracks show that a critical severity of deformation is required for growth to occur. Above this deformation the rate of single crack growth is essentially independent of strain and for a number of rubbers at normal temperatures is proportional to the ozone concentration. The mechanics of cracking in stretched surfaces is more complex, the rate of growth being dependent on strain and on various other factors such as the gas flow conditions and the test piece size. It is shown that these effects are consistent with diffusion control of the rate of attack; this occurs because the rapidity with which ozone is destroyed by stretched rubber leads to a reduced concentration adjacent to a surface. Certain chemical antiozonants can completely prevent cracking, even at very high deformations. Current investigations suggest that this is due to the formation of a protective layer on the surface of the rubber by direct reaction of the antiozonant with ozone; the diffusion of unreacted antiozonant is an important factor influencing layer development. It appears that the amount of antiozonant required for protection may be determined by the rate at which a coherent layer can be formed in relation to the rate at which ozone is attacking the surface.

Numerical Simulation of Bubble Formation in Co-Flowing Mercury

2008 ◽  
Author(s):  
Ashraf Ibrahim ◽  
Mark Wendel ◽  
David Felde ◽  
Bernard Riemer
Keyword(s):  
Acoustic Waves ◽  
Bubble Growth ◽  
Gas Flow ◽  
Bubble Formation ◽  
Science Center ◽  
Proton Radiography ◽  
Two Phase ◽  
Vof Model ◽  
Computational Fluid Dynamics Cfd ◽  
Bubble Sizes

In this work, we present computational fluid dynamics (CFD) simulations of helium bubble formation and detachment at a submerged needle in stagnant and co-flowing mercury. Since mercury is opaque, visualization of internal gas bubbles was done with proton radiography (pRad) at the Los Alamos Neutron Science Center (LANSCE2). The acoustic waves emitted at the time of detachment and during subsequent oscillations of the bubble were recorded with a microphone. The Volume of Fluid (VOF) model was used to simulate the unsteady two-phase flow of gas injection in mercury. The VOF model is validated by comparing detailed bubble sizes and shapes at various stages of the bubble growth and detachment, with the experimental measurements at 1.66 mg/min helium gas flow rate and different mercury velocities. The experimental and computational results show a two-stage bubble formation in stagnant mercury. The first stage involves growing bubble around the needle, and the second follows as the buoyancy overcomes wall adhesion. The comparison of predicted and measured bubble sizes and shapes at various stages of the bubble growth and detachment is in good agreement.

A Comparison Between PSRK and GERG-2004 Equation of State for Simulation of Non-Isothermal Compressible Natural Gases Mixed with Hydrogen in Pipelines / Porównanie równań stanu opracowanych według metody PSRK oraz GERG-2004 wykorzystanych do symulacji zachowania ściśliwych mieszanin gazu ziemnego i wodoru w rurociągach, w warunkach przepływów nie-izotermicznych

2013 ◽  
Vol 58 (2) ◽  
pp. 579-590
Author(s):  
Frits E. Uilhoorn
Keyword(s):  
Equation Of State ◽  
Natural Gas ◽  
Gas Flow ◽  
Transient Flow ◽  
Equations Of State ◽  
Group Contribution Method ◽  
Flow Conditions ◽  
Fluid Approximation ◽  
Natural Gases

In this work, the GERG-2004 equation of state based on a multi-fluid approximation explicit in the reduced Helmholtz energy is compared with the predictive Soave-Redlich-Kwong group contribution method. In the analysis, both equations of state are compared by simulating a non-isothermal transient flow of natural gas and mixed hydrogen-natural gas in pipelines. Besides the flow conditions also linepack-energy and energy consumption of the compressor station are computed. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum and energy. A pipeline section of the Yamal-Europe gas pipeline on Polish territory has been selected for the case study.

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