On the origin of the driving force in the Marangoni propelled gas bubble trapping mechanism

2017 ◽  
Vol 19 (28) ◽  
pp. 18695-18703 ◽  
Author(s):  
A. Miniewicz ◽  
C. Quintard ◽  
H. Orlikowska ◽  
S. Bartkiewicz
Keyword(s):  
Driving Force ◽  
Gas Bubbles ◽  
Gas Bubble ◽  
Particle Trajectories ◽  
Trapping Mechanism ◽  
Bubble Trapping

Particle trajectories around gas bubbles due to Marangoni induced flows of liquid.

Gas bubble induced scalings in geothermal systems

2021 ◽  
Author(s):  
Lilly Zacherl ◽  
Thomas Baumann
Keyword(s):  
Ph Value ◽  
Saturation Index ◽  
Gas Bubbles ◽  
Gas Bubble ◽  
Geothermal Systems ◽  
Injection Wells ◽  
Term Operation ◽  
Maintenance Schedule ◽  
Local Experience ◽  
Maintenance Schedules

<p>Scalings in geothermal systems are affecting the efficiency and safety of geothermal systems. An operate-until-fail maintenance scheme might seem appropriate for subsurface installations where the replacement of pumps and production pipes is costly and regular maintenance comprises a complete overhaul of the installations. The situation is different for surface level installations and injection wells. Here, monitoring of the thickness of precipitates is the key to optimized maintenance schedules and long-term operation.</p><p>A questionnaire revealed that operators of geothermal facilities start with a standardized maintenance schedule which is adjusted based on local experience. Sensor networks, numerical modelling and predictive maintenance are not yet applied. In this project we are aiming to close this gap with the development of a non-invasive sensor system coupled to innovative data acquisition and evaluation and an expert system to quantitatively predict the development of precipitations in geothermal systems and open cooling towers.</p><p>Previous investigations of scalings in the lower part of production pipes of a geothermal facility suggest that the disruption of the carbonate equilibrium is triggered by the formation of gas bubbles in the pump and subsequent stripping of CO<sub>2</sub>. Although small in it's overall effect on pH-value and saturation index, significant amounts of precipitates are forming at high volumetric flow rates. To assess the kinetics of gas bubble induced precipitations laboratory experiments were run. The experiment addresses precipitations at surfaces and at the gas bubbles themselves.</p>

Nuclei and Cavitation

1970 ◽  
Vol 92 (4) ◽  
pp. 681-688 ◽  
Author(s):  
J. William Holl
Keyword(s):  
Bubble Growth ◽  
Scale Effects ◽  
Gas Bubbles ◽  
Gas Content ◽  
Gas Bubble ◽  
Cavitation Nuclei ◽  
The Stability

This paper is a review of existing knowledge on cavitation nuclei. The lack of significant tensions in ordinary liquids is due to so-called weak spots or cavitation nuclei. The various forms which have been proposed for nuclei are gas bubbles, gas in a crevice, gas bubble with organic skin, and a hydrophobic solid. The stability argument leading to the postulation of the Harvey model is reviewed. Aspects of bubble growth are considered and it is shown that bubbles having different initial sizes will undergo vaporous cavitation at different liquid tensions. The three modes of growth, namely vaporous, pseudo, and gaseous are presented and implications concerning the interpretation of data are considered. The question of the source of nuclei and implications concerning scale effects are made. The measurement of nuclei is considered together with experiments on the effect of gas content on incipient cavitation.

An Electrochemically Actuated Micro Dosing System With Improved Dosing Control

1999 ◽  
Author(s):  
Sebastian Böhm ◽  
Wouter Olthuis ◽  
Piet Bergveld
Keyword(s):  
Driving Force ◽  
Gas Bubbles ◽  
Back Reaction ◽  
Integrated Sensor ◽  
Bubble Generation ◽  
Sensor Actuator ◽  
The Past ◽  
Electrolyte Mixture ◽  
Measured Impedance ◽  
Oxygen Gas

Abstract In this contribution a micromachined electrochemically-actuated micro dosing system is presented, which accurately can manipulate fluids in microsystems in the nanoliter range. The driving force to actively dispense liquids is provided by the electrochemical generation of gas bubbles (hydrogen and oxygen) by the electrolysis of an electrolyte. As these bubbles expand, they indirectly drive liquid out of a liquid filled reservoir, which is in hydraulic contact with the electrolyte in the bubble reservoir. The dosing system consists basically of a micromachined channel/reservoir structure in silicon, realized by dry reactive ion etching (DRIE). On top of this silicon fluidic board, a Pyrex® cover is bonded on which a set of electrodes is structured. These electrodes are applied for the generation of gas bubbles and at the same time, to measure the impedance of the gas/electrolyte mixture that is formed after bubble generation. It will be shown that this measured impedance reflects the gas bubble fraction in the bubble reservoir and that this parameter can be applied in determining the dosed amount of fluid. Besides the integrated sensor/actuator electrodes, measures have been taken to reduce the catalytic back reaction from the hydrogen oxygen gas mixture to water, as have been observed in the past.

Behavior of Inert Gas Bubbles in Forced Convective Liquid Metal Circuits

1976 ◽  
Vol 98 (1) ◽  
pp. 5-11 ◽  
Author(s):  
W. J. Minkowycz ◽  
D. M. France ◽  
R. M. Singer
Keyword(s):  
Liquid Metal ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Liquid Sodium ◽  
Gas Bubble ◽  
Flowing Liquid ◽  
Argon Gas ◽  
The Core

Conservation equations are derived for the motion of a small inert gas bubble in a large flowing liquid-gas solution subjected to large thermal gradients. Terms which are of the second order of magnitude under less severe and steady-state conditions are retained, thus resulting in an expanded form of the Rayleigh equation. The bubble dynamics is a function of opposing mechanisms tending to increase or decrease bubble volume while being transported with the solution. Diffusion of inert gas between the bubble and the solution is one of the most important of these mechanisms included in the analysis. The analytical model is applied to an argon gas bubble flowing in a weak solution of argon gas in liquid sodium. Calculations are performed for these fluids under conditions typical of normal and abnormal operation of a liquid metal fast breeder reactor (LMFBR) core and the resulting bubble radius, internal gas pressure, and mass of inert gas are presented in each case. An important result obtained indicates that inert gas bubbles reaching the core inlet of an LMFBR will always grow as they traverse the core under normal and extreme abnormal conditions and that the rate of growth is quite small in all cases.

Low Level Iodine Detection by TXRF in a Reactor Safety Simulation Experiment

1986 ◽  
Vol 30 ◽  
pp. 85-88 ◽  
Author(s):  
F. Hegedüs ◽  
P. Winkler ◽  
P. Wobrauschek ◽  
Christina Streli
Keyword(s):  
Simulation Experiment ◽  
Fission Products ◽  
Gas Bubbles ◽  
Vapor Concentration ◽  
Gas Bubble ◽  
Iodine Vapor ◽  
Reactor Safety ◽  
Water Pool ◽  
Federal Institute ◽  
Water Moderator

In the event of an accident in a light water moderated nuclear plant, the fission products escape from the water moderator in form of gas bubbles. One of the most important fission products is Iodine. Presently there are only rough estimations of the escape of Iodine. The aim of the experiment planned at the Swiss Federal Institute for Reactor Research (EIR) is to simulate the conditions of an accident and to measure the amount of Iodine which escapes from the moderator water into the space inside the reactor containment.It is supposed that at 5 m depth in a water pool, the canning of the fuel element explodes releasing 1-3 liter large gas bubbles containing the volatile fission products. The Iodine vapor concentration, saturated in the gas bubble, will be about 3 mg/l. It is expected that the water strongly absorbs the Iodine vapor and the I concentration in the gas bubble arriving at the water surface will be strongly reduced to a few ug/l.

Driving force of gas-bubble growth and dissolution

2018 ◽  
pp. 49-62 ◽  
Author(s):  
Saul Goldman ◽  
J. Manuel Solano-Altamirano ◽  
Kenneth M. Ledez
Keyword(s):  
Bubble Growth ◽  
Driving Force ◽  
Gas Bubble

scholarly journals Hydrodynamic interaction between gas bubbles in liquid

1976 ◽  
Vol 77 (1) ◽  
pp. 27-44 ◽  
Author(s):  
L. Van Wijngaarden ◽  
D. J. Jeffrey
Keyword(s):  
Relative Motion ◽  
Momentum Flux ◽  
Hydrodynamic Interaction ◽  
Liquid Mixture ◽  
Gas Bubbles ◽  
Gas Bubble ◽  
Virtual Mass ◽  
Bubble Liquid ◽  
The One

A calculation is given of the velocity which a cloud of identical gas bubbles acquires when the liquid in which the cloud is immersed is impulsively accelerated. From the results an expression follows for the effective virtual mass of a bubble in a gas-bubble/liquid mixture. Further consideration is given to that part of the momentum flux in the mixture associated with relative motion between liquid and bubbles. An expression for this quantity is derived which appears to differ from the one used in practice. It is shown that qualitative support for the expression obtained here is provided by experimental observations reported in the literature.

The velocity of rise of distorted gas bubbles in a liquid of small viscosity

1965 ◽  
Vol 23 (4) ◽  
pp. 749-766 ◽  
Author(s):  
D. W. Moore
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Gas Bubbles ◽  
Quantitative Agreement ◽  
Terminal Velocity ◽  
Dimensionless Group ◽  
Gas Bubble ◽  
Numerical Accuracy ◽  
Small Viscosity ◽  
Acceleration Of Gravity

The terminal velocity of rise of small, distorted gas bubbles in a liquid of small viscosity is calculated. Small viscosity means that the dimensionless group gμ4/ρT3 where g is the acceleration of gravity, μ the viscosity, ρ the density and T the surface tension, is less than 10−8. It is assumed—and the numerical accuracy of the assumption is discussed—that the distorted bubbles are oblate ellipsoids of revolution. The drag coefficient is found by extending the theory given recently (Moore 1963) for the boundary layer on a spherical gas bubble. The results are in reasonable quantitative agreement with the experimental data.

The Influence of Velocity and Scale on Cavitation Inception where Wall-Generated Gas Bubbles are the Sole Source of Cavitation Nuclei

1975 ◽  
Vol 17 (2) ◽  
pp. 45-51
Author(s):  
M. R. Baum
Keyword(s):  
Bubble Growth ◽  
Flow System ◽  
Scale Effects ◽  
Gas Bubbles ◽  
Sole Source ◽  
Gas Bubble ◽  
Cavitation Inception ◽  
Boundary Wall ◽  
Cavitation Nuclei ◽  
System Properties

It is established, using recently derived expressions relating the flow system properties to the size at which a gas bubble grown at a boundary wall will become detached, that the commonly observed variation in cavitation inception pressure with velocity in a given system can be simply attributed to variations in the size of bubble detached. However, it is concluded, from a comparison of predicted and experimental variations of inception pressure with scale of the system, that when considering scale effects the pressure necessary to promote gas-bubble growth must also be taken into account.

Mathematical Model of Gas Bubble Evolution in a Straight Tube

1999 ◽  
Vol 121 (5) ◽  
pp. 505-513 ◽  
Author(s):  
D. Halpern ◽  
Y. Jiang ◽  
J. F. Himm
Keyword(s):  
Decompression Sickness ◽  
Ambient Pressure ◽  
Fluid Motion ◽  
Gas Bubbles ◽  
Coupled System ◽  
Bubble Surface ◽  
Inert Gas ◽  
Straight Tube ◽  
Gas Bubble ◽  
Bubble Evolution

Deep sea divers suffer from decompression sickness (DCS) when their rate of ascent to the surface is too rapid. When the ambient pressure drops, inert gas bubbles may form in blood vessels and tissues. The evolution of a gas bubble in a rigid tube filled with slowly moving fluid, intended to simulate a bubble in a blood vessel, is studied by solving a coupled system of fluid-flow and gas transport equations. The governing equations for the fluid motion are solved using two techniques: an analytical method appropriate for small nondeformable spherical bubbles, and the boundary element method for deformable bubbles of arbitrary size, given an applied steady flow rate. A steady convection-diffusion equation is then solved numerically to determine the concentration of gas. The bubble volume, or equivalently the gas mass inside the bubble for a constant bubble pressure, is adjusted over time according to the mass flux at the bubble surface. Using a quasi-steady approximation, the evolution of a gas bubble in a tube is obtained. Results show that convection increases the gas pressure gradient at the bubble surface, hence increasing the rate of bubble evolution. Comparing with the result for a single gas bubble in an infinite tissue, the rate of evolution in a tube is approximately twice as fast. Surface tension is also shown to have a significant effect. These findings may have important implications for our understanding of the mechanisms of inert gas bubbles in the circulation underlying decompression sickness.

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