Bubble Count Research Articles

Novel Capped-Needle Device: A Novel Safety Feature to Eliminate Air Bubbles in Hemodialysis

Introduction: Air bubbles in the dialysis circuit are rarely visible after automatic priming; however, they are often visible after the needles are manually connected to the circuit. To prevent this issue, we thought to prime needles with a circuit at automatic priming by the hemodialysis machine. In order to achieve this idea, we designed and manufactured a novel capped needle to connect the needles to the extracorporeal circuit before the automatic priming of the hemodialysis machine. This study investigated the effectiveness of this novel capped needle and compared it with the conventional method for preventing air bubble contamination. Methods: We tested novel capped needles ten times to evaluate whether the dialysis machine works appropriately and removes air bubbles even with the attached capped needle. Next, we performed 25 trials using the conventional method, in which skilled nurses manually connect the needle. In both methods, we thoroughly counted the air bubbles with our naked eyes. We predicted that the capped needle would leave few bubbles in the circuit. In order to evaluate fewer bubbles, we conducted an additional experiment using a microparticle counter to measure the size and number of the bubbles. Results: We thoroughly searched for air bubbles during each of the ten tests but could not find any bubbles visible to the naked eye. In the conventional method, bubbles were visible in 29 out of 50 cases. The bubble count was significantly lower in the capped-needle method than in the conventional method (p < 0.0001, Pearson’s χ² test). In the additional experiments using the microparticle counter, the average remaining air volume in the extracorporeal circuit was 0.0999 ± 0.2438 nL when the priming was performed using the novel capped needles. Conclusion: The novel capped needle eliminated all visible bubbles efficiently and effectively; therefore, it could be a valuable device for hemodialysis treatment. The reduction of air from the dialysis circuit may improve patient prognosis.

Air‐Water Mixing in Vegetated Supercritical Flow: Effects of Vegetation Roughness and Water Temperature on Flow Self‐Aeration

AbstractVegetated flow is rarely investigated for supercritical flow regime, in which self‐aeration occurs and modifies the flow dynamics, energy dissipation, and mass transfer between the water body and ambient air environment. In this study, natural river water was used at two flow rates in combination with six bottom vegetation conditions to investigate the air‐water flow development in an 18‐m‐long sloping chute. The vegetation configurations included two artificial turfs with different grass lengths and three flexible plant covers with different canopy densities, in addition to a reference case of smooth solid boundary, providing flow resistance and turbulent disturbance with different orders of equivalent roughness heights. Physical measurements were focused on the air concentration, free‐surface splashing, turbulent velocity, bubble count frequency, and bubble size distributions from the upstream non‐aerated flow to the far‐field fully developed aeration region. Compared to the velocity developing to uniform equilibrium shortly downstream the inception of aeration, the flow self‐aeration reached air‐concentration equilibrium at further downstream positions, while the bubble count and air‐water interfacial area kept increasing. The vegetation roughness conditions affected the inception location, equivalent bubble rise velocity, superfacial splashing height, velocity gradient, and maximum bubble count near the free surface, whereas the equilibrium air concentration in the fully developed region depended only upon the slope. The vegetation type influenced the percentage of submillimetre bubbles. Little differences were shown in the air‐water flow characteristics by repeating the summer experiments in winter with a 25.5°C drop in water temperature, despite the variation in fluid viscosity thus the Reynolds number under identical discharge.

Improvements on time-resolved measurement of gas volume production in laboratories bench systems

We propose improvements to a time-resolved gas volume meter based on bubble count. This type of sensor is dedicated to small-scale laboratory applications, usually related to gas production in biological processes. We highlight the cost reduction and simplification in the manufacturing method of this type of sensor, when compared to the manufacturing method. To achieve this purpose, the sensor’s glass body was replaced by plastic material, a detection system based on the detection of capacitance variation was introduced and without contact with the measuring fluid, the data acquisition system was built based on small single-board computer and a graphical user interface were developed in an open source programming language. Theses innovations are significant for scientific research institutions, with limited financial resources, to uses gas volume sensors that can be applied in the investigation of biological processes such as alcoholic fermentation, biogas and biohydrogen generation.

Learning new physical descriptors from reduced-order analysis of bubble dynamics in boiling heat transfer

Understanding bubble dynamics during boiling is challenging due to the drastic changes in system parameters, such as nucleation, bubble morphology, temperature, and pressure. In this study, principal component analysis (PCA), an unsupervised dimensionality reduction algorithm, is used to extract new physical descriptors of boiling heat transfer from pool boiling experimental images without labeling and training. The dominant frequency and amplitude of the time-series principal components (PCs) are analyzed, where the first few dominant PCs are used to approximate the instantaneous bubble morphologies, drastically reducing the data dimensions. The results show that the dominant frequency and amplitude can be used as new physical descriptors to distinguish different boiling regimes. The dominant frequency of the first PC is found to increase with heat flux in the discrete bubble regime until it reaches a peak and then decreases with heat flux in the bubble interference and coalescence regime, where the former is believed to be associated with the increase in bubble nucleation sites and the latter is associated with the bubble coalescence during pool boiling. The dominant frequency and amplitude extracted from the present unsupervised learning are qualitatively compared to the bubble count and size extracted from a supervised deep-learning algorithm, and the approach appears highly robust over multiple datasets and heater surfaces. To predict future boiling states for mitigating boiling crises, bidirectional long short-term memory (BiLSTM) neural network is used to estimate the future variations of PCs and hence the bubble dynamics, from time-series PCs. The PCA-BiLSTM models predict reduced-order bubble images well and show significantly higher prediction accuracy compared to the Convolutional-LSTM.

Physiology of repeated mixed gas 100-m wreck dives using a closed-circuit rebreather: a field bubble study.

PurposeData regarding decompression stress after deep closed-circuit rebreather (CCR) dives are scarce. This study aimed to monitor technical divers during a wreck diving expedition and provide an insight in venous gas emboli (VGE) dynamics.MethodsDiving practices of ten technical divers were observed. They performed a series of three consecutive daily dives around 100 m. VGE counts were measured 30 and 60 min after surfacing by both cardiac echography and subclavian Doppler graded according to categorical scores (Eftedal–Brubakk and Spencer scale, respectively) that were converted to simplified bubble grading system (BGS) for the purpose of analysis. Total body weight and fluids shift using bioimpedancemetry were also collected pre- and post-dive.ResultsDepth-time profiles of the 30 recorded man-dives were 97.3 ± 26.4 msw [range: 54–136] with a runtime of 160 ± 65 min [range: 59–270]. No clinical decompression sickness (DCS) was detected. The echographic frame-based bubble count par cardiac cycle was 14 ± 13 at 30 min and 13 ± 13 at 60 min. There is no statistical difference neither between dives, nor between time of measurements (P = 0.07). However, regardless of the level of conservatism used, a high incidence of high-grade VGE was detected. Doppler recordings with the O’dive were highly correlated with echographic recordings (Spearman r of 0.81, P = 0.008).ConclusionAlthough preliminary, the present observation related to real CCR deep dives questions the precedence of decompression algorithm over individual risk factors and pleads for an individual approach of decompression.

High-Velocity Air–Water Flow Measurements in a Prototype Tunnel Chute: Scaling of Void Fraction and Interfacial Velocity

Aeration occurs in many natural and human-made flows and must be considered in engineering design. In water infrastructure, air–water flows can be violent and of very high velocity. To date, most fundamental research and engineering design guidelines involving air–water flows have been based upon laboratory scale measurements with limited validation at prototype scale with larger Reynolds numbers. Herein, unique measurements were conducted in high-velocity air–water flows in the tunnel chute of the 225-m-high Luzzone arch Dam in Switzerland. For each of the two test series, an array of 16 double-tip conductivity probes was installed in the circular tunnel chute of 3 m diameter and slope of ≈37° measuring void fraction, bubble count rate, interfacial velocity, and droplet sizes for four different discharges of up to 15.9 m3/s corresponding to Reynolds numbers of up to 2.4 × 107 and mean flow velocities of up to 38 m/s. Void fraction and interfacial velocity distributions, as well as design parameters such as depth-averaged void fractions and flow resistance, compared well with previous laboratory studies and empirical equations. The droplet chord sizes exhibited scale effects, and care must be taken if air–water mass transfer and droplet momentum exchange processes are assessed at the laboratory scale.

Air-Water Flow Properties in Hydraulic Jumps With Fully and Partially Developed Inflow Conditions

Abstract Novel air–water flow measurements were conducted in fully aerated hydraulic jumps with partially and fully developed supercritical inflow conditions. Irrespective of the inflow conditions, the hydraulic jumps resembled typical flow patterns with strong aeration and instabilities, albeit hydraulic jumps with fully developed inflow conditions had a more upward directed roller motion and a larger clear water core in the second half of the roller. Hydraulic jumps with fully developed inflow conditions had comparatively larger void fractions in the first half of the jump roller and larger bubble count rates throughout, while a comparatively larger number of smaller bubble sizes suggested a stronger break-up of bubbles. This was consistent with slightly larger interfacial velocities and turbulence intensities in the first half of the jump roller with fully developed inflow conditions. An assessment of the required sampling duration for air–water flow properties indicated the requirement to sample for at least five times longer than applied in previous studies. These results highlighted the need to carefully consider the inflow conditions and sampling parameters for aerated hydraulic jumps.

Physio-Chemical Analysis of Amide and Amine Poly(dimethylsiloxane)-Modified Defoamer for Efficient Oil-Water Separation.

The formation of foam due to the injection of surfactant foam in FAWAG causes significant problems in the oil well production and separation facilities. The excessive foam can lead to the reduction of the separator capacity as well as its efficiency. A defoamer is needed to break and destroy the foam in the separator. There are many commercially available defoamer agents in the market, but not all defoamers are suitable for every application. For this reason, four modified silicone-based defoamers were successfully synthesized and characterized based on the data obtained from the screening process using various commercial defoamers. The performance of modified defoamers was evaluated using TECLIS FoamScan that imitate real conditions of treatment. The results show that all four of the modified silicone-based defoamers, especially amide-terminated-modified defoamers (S2) showed excellent performance as a defoaming agent to mitigate foam in specific conditions. The best-case condition for the modified defoamer to perform was at a high temperature (60 °C), gas flow rate of 1.0 L/min, and low ration concentration of the surfactant to brine (30:70). The study on the bubble count and distribution using a KRÜSS Dynamic Foam Analyzer revealed that S2 excellently contributes to the formation of unstable foam that can fasten foam destruction in the foaming system.

MO665THE BRAND-NEW NEEDLE CAP ELIMINATES ALL VISIBLE AIR BUBBLES DURING THE AUTOMATIC PRIMING PROCESS OF HEMODIALYSIS MACHINES

Abstract Background and Aims The air contamination from the dialysis circuit into the patient's body is an unsolved serious problem. Recently, Automatic priming function of dialysis machines is widely used. There are rarely any air bubbles left in the extracorporeal circuit after automatic priming of the dialysis machines. To use this method, the arterial and venous sides of the extracorporeal circuit are connected to create a closed circuit so that dialysate can circulate and overflowed through a line from this closed circuit. However, air bubbles may enter when disconnecting the closed extracorporeal circuit and attaching the needles. We tried to solve this problem by simply connecting the arterial and venous needles to the extracorporeal closed circuit before the process of automatic priming process. To prime the whole extracorporeal circuit with needles, we had made a brand-new suitable cap of the needle, which is tightly connected with a needle and has an open end. (Fig) This special cap allows the needle to be incorporated into the closed circuit prior to the automatic priming process, allowing the dialysis machine to completely remove the air during priming process. The purpose of this study is to present the details of this new method and compare its effectiveness in preventing air bubble contamination between the traditional method and this new method. Method A prospective, non-randomized, comparative study was conducted to verify whether air remained grossly visible after the needle was connected to the extracorporeal circuit. The traditional method: DCS-100NX (Nikkiso Co Ltd, Tokyo Japan) was used for extracorporeal circuit priming. After the automatic priming was finished. Nurses disconnect the arterial and venous side of the extracorporeal circuit and connect both ends to the needles by hands. The nurse operates the dialysis machine to blow the small amount of dialysate out of the needle and tried to remove the air. It takes nearly 2minutes in each case. We examined the extracorporeal circuits consecutively. New cap-based method: The needles were connected to the closed circuit with the new cap and auto-primed by the dialysis machine N100. Automatic priming, including the needle were performed consecutively. In each method, we thoroughly checked for any remaining macro bubbles with the naked eye. Since bubbles in the extracorporeal circuit on the arterial side are likely to be supplemented by the air trap chamber, only bubbles on the venous side were compared. Results The study was conducted in October 15th to 24th 2020 at the Yokohama Minami Clinic. The traditional method: We checked 50 extracorporeal circuits consecutively. There were bubbles in the venous side of the extracorporeal circuits 29 times out of 50 times. New cap-based method: 10 consecutive automatic priming, including the needle was performed. DCS-100NX was used as the dialysis machine. There were no bubbles visible to the naked eye in the arterial and venous side of the circuit. Statistical Results There was a statistically significant difference of the bubble count between the traditional method and new cap-based method. (p=0.0001, Pearson's chi-square test) Conclusion All visible bubbles were removed automatically by simply connecting the needles using this brand-new cap before a process of automatic priming. This easy-to-use and highly effective cap could be considered an essential device for hemodialysis treatment like seat belts in automobiles.

Characterization of bubble detectors for space application

A passive neutron-bubble dosimeter, developed by Bubble Technology Industries, has been used for space applications. This study provides a means to characterize the response of these detectors to various particle types in support of bubble-detector measurements made on a board the International Space Station (ISS) in Low Earth Orbit. An analysis of the radiation environment onboard the ISS in the Service Module with the OLTARIS code indicates that neutrons, protons, and lower atomic mass particles are the more abundant particles. Based on a Monte Carlo treatment with the Stopping Range of Ions in Matter (SRIM) code, the response functions of the lighter ions were determined. This assessment considered the maximum linear energy transfer of these ions at the end of their path (Bragg peak) in the detector that exceeded the minimum threshold to cause bubble nucleation. The model was benchmarked against previous heavy-ion measurements in ground-based accelerator studies. The model was able to successfully predict, for a beam oriented along the detector axis, the observed energies at which the ions penetrated and exited the detector as well as the relative scaling of the response curves. By folding in the calculated particle fluxes with both the predicted light-ion response functions, as well as using experimental responses for neutrons, protons and alpha particles measured in previous accelerator studies, the contribution of particles in space to the bubble count was evaluated. This analysis shows that for an isotropic-irradiation geometry in space, neutrons are the major contributors to the bubble count with a much smaller contribution from protons.

Foam bubble size is significantly influenced by sclerosant concentration for polidocanol but not sodium tetradecyl sulphate

To determine the effect of liquid gas fraction (LGF), sclerosant type and concentration, and filter use on foam bubble size and count. Sclerosant foam microstructure was investigated using light microscopy for a range of LGFs (1 + 2, 1 + 4 and 1 + 8), for both sodium tetradecyl sulphate (STS) and polidocanol (POL), at a range of concentrations (0.5-3%), with and without the addition of micro-filters. Foam was generated using a modified Tessari method and placed into wells for analysis by light microscopy. Foam microscopic morphology was photographically documented, and bubble diameters and counts were quantified. Spherical bubbles were observed at lower LGF and a trend towards polyhedral morphology was observed at the higher LGF of (1 + 8). The higher gas content in LGF led to larger but fewer bubbles. POL bubble diameters appeared to be more influenced by concentration than STS with smaller bubbles observed at higher concentrations of POL. The mean bubble diameters were slightly larger for STS than POL at the highest concentration of 3% but smaller at lower concentrations of 1% and 1.5%. LGF is the primary determinant of bubble diameter and count. In contrast to STS, POL concentration influences the foam bubble size with smaller bubbles generated at higher concentrations of POL and larger bubbles appearing at low concentrations of this agent.

Bubble characteristics affecting air-water exchange in open-channel flow with a jet forming over a sudden bottom drop

Entrainment of air bubbles into flowing water increases significantly the interfacial area between the two phases hence enhancing the air-water mass transfer. The air bubble characteristics are thus of direct relevance to the waterbody aeration and oxygenation, which should be understood in the context of bubbly-flow turbulence development. In this paper, we studied experimentally a canonical aerated flow featured by a two-dimensional jet over a sudden bottom drop followed by a sloping open-channel flow. This is a representative scenario of open-channel flow with simultaneous free-surface air-water exchange and bottom aeration into the deep water. In addition to the air concentration and air flux evolutions upstream and downstream of the jet impact on the channel bed as well as from bottom to the free-surface, the local and accumulative bubble count rate distributions were depicted. The air-water flow structures were revealed at bubble scales with the aid of a further characterisation of the bubble chord length spectrum and mean bubble size distributions, indicating intense bubble breakups following the jet impact and next to the bottom boundary layer. Although the jet impact on the dry bottom was responsible for a substantial air loss, an increasing number of smaller bubbles were produced and prevented drastic drop in the air-water interfacial area. The mean bubble size and specific interfacial area were predicted under some rough assumption for the deep-water mass transfer. An insight into the bubble-turbulence interplay was presented based on a statistic bubble clustering analysis.

Estimation of air-flow parameters and turbulent intensity in hydraulic jump on rough bed using Bayesian model averaging

A hydraulic jump is an abrupt transition between subcritical and supercritical flows which is associated with energy dissipation, air entrainment, spray, splashing, and surface waves. Both physical and numerical modeling were largely applied to study hydrodynamics, turbulence and air-entrainment in the hydraulic jump, while the literature about the application of classifier models is quite limited. Determining air-flow parameters and turbulent intensity has been merely performed by costly and time-consuming experimental methods, while this study is the first attempt to estimate the mentioned parameters using a computer-based methodology with desired precision. In the present study, air-flow parameters including void fraction (C) and bubble count rate (F), as well as turbulent intensity (Tu) on rough bed were estimated using Bayesian model averaging (BMA) and three multilayer perceptron (MLP), support vector regression (SVR) and generalized regression neural network (GRNN) as classifier models. To develop the stated models, the experimental data from Felder and Chanson (2016) were divided into four classes based on longitudinal distance from the jump toe. Results highlighted that the MLP and GRNN models have more accurate results compared to the SVR model. For F and Tu, the GRNN model and for C, the MLP model showed better performance than other models in four classes. The average acceptance rate between 15 and 30% of the BMA model performance for all classes proved the accuracy and efficiency of the proposed methodology. The average RMSE value of BMA results and the bests classifier models were 0.41 and 0.42, respectively, for the estimation of all three parameters. Results revealed that the BMA model by weighting individual classifier models could be able to estimate parameters with better accuracy than the best classifier model in each class. The significant outcome of this study is that the proposed model is able to render accurate results in a complex system such as hydraulic jump.

Experiments on air entrainment produced by a circular free falling jet

The process of a circular free falling jet entering an idle pool was studied with the objective of determining a relation between the naturally occurring disturbances on the jet surface and air entrainment. To this end the instabilities of the free falling jet were characterized and compared with the bubble count distribution and an estimated amount of entrained air in the plume. Different jet lengths were considered. The aeration process was captured through image sequences. Individual analysis of each disturbance in the jet surface was made. Our results show that both the bubble count and entrained air have a linear relation with the steepness of the jet disturbances. Moreover, the wave-jet ratio is introduced, which defines an entrainment condition for all the studied cases.

Singular air entrapment at vertical and horizontal supported jets: plunging jets versus hydraulic jumps

In plunging jets and at hydraulic jumps, large amounts of air bubbles are entrained at the impingement of the liquid jet into the receiving body. Air is entrapped and advected into a turbulent shear layer with strong interactions between the air bubble advection process and momentum shear flow. In this new physical study, air-water flow measurements were systematically repeated with identical inflow length, inflow depth and inflow velocity in a vertical supported jet (PJ) and a horizontal hydraulic jump (HJ). Detailed measurements were conducted with the same instrumentation. Both similarities and differences were observed between the two multiphase gas-liquid shear flows. Visual observations showed a key difference in the outer region, with a buoyancy-driven flow in the plunging jet with negligible void fraction, versus a strong recirculation motion with uncontrolled interfacial aeration in the hydraulic jump. Differences were also observed at the impingement perimeter, in terms of fluctuation frequencies and amplitudes, for identical inflow conditions. Both flow conditions yielded intense local singular air entrainment and close results were observed in terms of void fraction, bubble count rate, bubble chord sizes and interfacial area in the shear layer, in both the plunging jet and hydraulic jump. The transfer of momentum between impinging jet and receiving water, as well as the effect of buoyancy, were however affected by the flow geometry.

Production-Logging Technologies Enhance Inflow Profiling in Deepwater Gulf of Mexico

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 196188, “Third-Generation Production-Logging Technologies Enhance Inflow Profiling in Deepwater Gulf of Mexico Reservoirs,” by Glenn Donovan, SPE, Sagar Kamath, and Elizabeth Tanis, SPE, Shell, et al., prepared for the 2019 SPE Annual Technology Conference and Exhibition, Calgary, 30 September–2 October. The paper has not been peer reviewed. This paper discusses the effectiveness of third-generation (Gen3) production-logging-tool (PLT) technology, which uses co-located digital sensors for simultaneous acquisition of flow data to provide the most accurate characterization of the flow condition at each depth surveyed. The resulting data allow for much-improved processing. The probabilistic interpretive model used in the processing has been updated to incorporate this and future developments in PLT architecture. Introduction The first generation of PLT provided a single, discrete measurement for each sensor along the tool assembly’s length, resulting in long tool assemblies and measurements taken at different points along the flow path. This approach had several drawbacks: long toolstrings, point sensors that only provided a measurement at a single point in the cross section of the flow, and measurements that were not acquired simultaneously at each depth logged. Second- generation PLTs represented an improvement because sensors were arranged as an array, enabling multiple measurements to be made at a single depth. However, the toolstrings were still long and not all were arranged optimally to capture data in the flow path. The Gen3 PLT is one-tenth the length of the first-generation versions and roughly one-third that of the shortest second-generation tools. Digitalization allows for direct measurement of flow conditions and rapid interpretation of results. In multiphase flow and deviated wells, co-locating sensors in a spatial geometry provides the optimal information with which to create a fully accurate picture of the downhole flow. Description of Gen3 PLT The PLT described in the paper exemplifies how miniaturization and digitalization are enabling transformational improvements over traditional systems in terms of efficiency and capability. The tool encompasses, within a 3-ft length, up to 24 sensors that collect multiple measurements of fluid properties and fluid movements in a wellbore. These include oil, gas, and water holdup and bubble count, fluid conductivity, phase velocities, pressure, temperature, inclination, rotation, and depth correlation, plus power and communication. The fluid characteristics are locally screened by an array of 8 to 16 tube-shaped probe sensors that are interchangeable, depending on the targeted measurements (Fig. 1). The tool relies on a refractive index needle-shaped probe with a triphasic sensor to identify and quantify the oil, gas, and water holdups and bubble counts at each point of the array. The geometric design of the sensitive tip, along with the optoelectronics of the sensor, are optimized to discriminate oil, water, and gas with high confidence, overcoming the fact that the refractive indexes of oil and water are close to each other.

Flow Resistance and Energy Dissipation in Supercritical Air‐Water Flows Down Vegetated Chutes

AbstractVegetation covers on dikes and embankment dams have proven as sustainable and cost‐effective surface protection against external erosion caused by hydraulic, mechanical, or climatic impacts. Determination of the hydraulic loads that act upon these covers requires the knowledge of the flow resistance. While the high‐velocity flows on vegetated slopes are often aerated, the flow aeration has rarely been considered, and no direct measurements of the air‐water flow properties have been conducted to date. The air‐water flow properties are needed for a direct estimation of important design parameters such as friction factors and residual head at the downstream end. Herein, unique air‐water flow measurements were conducted in high‐velocity air‐water flows down a vegetated chute with a 1:3 slope. Several vegetation covers were tested for a range of flow rates. The experiments revealed strong flow aeration within three‐dimensional, fragmented flows associated with complex interactions of vegetation and high‐velocity flows. The air‐water flow properties were measured with phase‐detection intrusive probes providing novel insights into aerated flows on vegetated chutes including distributions of void fraction, bubble count rate, and interfacial velocity as well as direct estimates of energy dissipation and flow resistance. The results highlighted strong flow aeration and energy dissipation for all vegetated configurations. The median equivalent Darcy‐Weisbach friction factors for all vegetations were within 0.19 to 0.45, comparable to aerated flows on stepped spillways. The present results highlighted the significant flow resistance of vegetated covers and the need to consider air‐water flow properties in the design of vegetated chutes.

Volume and rate measurement of slowly generated gas bubbles

The use of an inverted burette arrangement that allowed volume and time-course tracking of bubble movement via camera imaging is shown here to improve on the classical inverted jar (or beaker) method for measuring gases generated in small volumes and at slow rates (below 1 mL/s). In tests involving discrete gas volume measurements delivered at 0.57 mL/s, comparison with pre-set air volume delivered by a syringe pump showed high correspondence, linearity, and repeatability. Tests with continuous gas flows at 0.2, 0.32 and 0.57 mL/s revealed average bubble count versus volume trends that displayed high linearity to indicate that the bubble volumes (at any flowrate) were constant. The average bubble count versus time also showed linear trends and repeatability indicating that the time intervals between the appearance of any two bubbles (at a particular flowrate) were uniform. The analytical and simulated results helped to explain why bubble size determination by high speed camera recording for measuring gas volume and flowrate is fraught with inherent problems. An analysis using light ray tracing showed that flowrate determination using such an approach would necessitate complicated image correction when two cameras are used for simultaneous recording due to distortion effects resulting from refraction. A virtual gate approach involving the binarization of images recorded with a standard camera is shown to be more feasible in establishing the flowrate using bubble counting or finding the time interval between bubbles.

Foamstability: The interplay between salt-, surfactant- and critical micelle concentration

It is central to understand the underlying factors that affect the generation and stabilization of foam. Nevertheless, reports on how foam stability is impacted by surfactant concentration, electrolyte concentration, and electrolyte nature are ambiguous. This paper summarizes the foaming properties below and above the critical micelle concentration (CMC) at various electrolyte concentrations. The commonly used surfactant, alpha olefin sulfonate (AOS), was used along with NaCl in a range of concentrations. The foam height, foam volume stability, bubble count, and foam structure were studied to determine the foam behavior at given conditions. The optimum surfactant concentration for the formation of a stable micellar film was found to be just above the CMC value and the foam stability on the addition of salts is related to the surfactant concentration. There exists another critical concentration (not CMC) that is important to determine the impact of salts on the stability of the foam. The addition of NaCl does not have the same impact below and above this critical concentration. If the concentration of surfactant is below the critical concentration, addition of NaCl reduces the half-life and foam stability. However, at higher surfactant concentrations, the presence of NaCl improves the half-life and foam stability. This study clarifies the ambiguities that are present in the literature pertaining to the effect of salt on foam stability and foaming properties.

Role of Counterions and Nature of Spacer on Foaming Properties of Novel Polyoxyethylene Cationic Gemini Surfactants

Application of foam in various upstream operations, such as in enhanced oil recovery, has gained significant attention in recent years. A good foaming agent should generate a stable foam, must be thermally stable (&gt;90 °C, typical reservoir temperature), must have a high tolerance to salinity, and should have low adsorption on the reservoir rock. In view of this, four thermally stable and salt-tolerant polyoxyethylene cationic gemini surfactants were synthesized with different spacers (mono phenyl and biphenyl) and different counterions (Br− and Cl−). Foaming properties were evaluated using initial foam generation, foam volume stability at a given time, bubble count, and average foam bubble radius. The effect of counterions and nature of spacers, with and without the presence of salts, on foaming properties was evaluated. It was found that number of phenyl rings (mono phenyl and biphenyl) had no significant effect on foamability and foam stability in the presence or absence of salts. However, the effect of counterions was prominent in deionized water. In deionized water, foam generated by gemini surfactants with bromide as a counterion was more stable compared to the foam generated using the surfactant containing chloride as the counterion. In saline solution, the type of counterion had no effect on the foamability or foam stability of the foam generated using synthesized cationic gemini surfactants. The foam volume stability decreased by the addition of salts; however, a further increase in salt concentration enhanced the foam volume stability. The synthesized surfactants showed good thermal stability, salt tolerance, and foaming properties and can be an attractive choice for upstream applications.