Low Liquid Flow Rates Research Articles

Effects of the divergent angle on bubble transportation in a rectangular Venturi channel and its performance in producing fine bubbles

Venturi-type bubble generator has a broad application in various fields and its performance depends on its geometrical size to a great extent. In present work, bubble movement, and breakup process in Venturi channels with different divergent angles were recorded by a high speed camera to further investigate the role of the divergent angle in bubble breakup. Three rectangular Venturi channels with the only difference in the divergent angles (7.5°, 10.0° and 12.5°) were tested at the liquid velocity of 0.67–10.0 m/s in the throat. Parameters relevant to bubble transportation, including bubble velocity, deceleration, breakup position and size distribution, etc., were obtained by Digital Image Analysis method from the video data. Results showed that bubbles experienced dramatic deceleration in the entrance of the diverging section, where an obvious stagnation region was observed. Strong interaction between the gas and liquid was resulted and gave rise to bubble breakup.The divergent angle had a significant influence on the deceleration process. For a larger divergent angle: (1) it took a shorter distance and time for bubbles to be decelerated to their minimum velocities; (2) more intensified interaction between the gas and liquid was resulted, generating smaller bubbles; (3) a lower liquid flow rate was required to induce bubble breakup. Finally, a modified correlation for predicting average bubble size in Venturi channels was proposed with the consideration of the effect of the divergent angle.

Popularization and application of the capillary foam deliquification technology in horizontal wells with low pressures and low liquid flow rates: A case study on middle–shallow gas reservoirs in the Western Sichuan depression

The application effect of the foam deliquification technology in horizontal wells is poor because the foaming agent fails to reach the target location. In view of this, the adaptability of the capillary foam deliquification technology in the Western Sichuan Gas Field in the Sichuan Basin was analyzed from the aspects of gas flow rate, liquid flow rate and casing program of gas wells, and the design of injection depth and the selection of capillary size, tool string parameters (the maximum length and the minimum counterweight) and foam deliquification parameters (foaming agent type selection, ground injection concentration and rate) were optimized. Then, a standardized capillary operation process was developed. Finally, a field application test was carried out. And the following research results were obtained. First, the capillary foam deliquification technology has a popularization potential in the horizontal wells of middle–shallow depth, low pressure and low liquid flow rate, but it is not suitable for the wells with too low gas flow rate, too high liquid flow rate or too high condensate content. Second, the well deviation angle at the injection depth shall be between 70° and 80°, the selection of capillary size shall satisfy the requirement for tension strength by the well depth, the foam deliquification parameters shall be optimized based on the specific well conditions and the liquid loading characteristics, and the capillary operation shall comply with the standardized process. Third, by the end of July 2017, the capillary foam deliquification technology had been successfully applied in 9 horizontal wells in the Western Sichuan Gas Field with a cumulative gas increment of 295 × 104 m3. Fourth, 4 supporting technologies of the capillary foam deliquification are formed, including capillary sticking prevention, integrated agent injection and pressure measurement, combined cleaning and deliquification and capillary wellhead suspension. In conclusion, the capillary foam deliquification technology provides a technological support for the deliquification and production stabilization of horizontal wells with middle–shallow depth, low pressures and low liquid flow rates in the Western Sichuan Depression, and also provides technological reference for the deliquification of horizontal wells in the similar type of gas reservoirs.

Heat transfer characteristics of obliquely dispensed evaporating falling films on an elliptic tube

This study examines the evaporation heat transfer characteristics of obliquely dispensed falling films over a horizontal elliptic tube. The theoretical model applied the volume-of-fluid (VOF) method to simulate the spreading development of falling liquid films for resolving the distributions of velocity, temperature, volume fraction in conjunction with the convective heat transfer coefficient. Specifically, a user defined function (UDF) was formulated to treat the evaporative effect at the liquid film surface to the environment. The predicted heat transfer coefficients and film thickness distributions around the circular and elliptic tube surfaces were validated by the experimental data from the available literatures. Based on the test results via comparing different flow models, the SST k-ω model provides the best capabilities in terms of the better prediction accuracy and less calculation time. CFD simulations were then extended using the validated computational model to explore the effects of inlet liquid mass flow rate and obliquely dispensed angle on the liquid film distribution and heat transfer characteristics over the horizontal elliptic tube. At a low liquid flow rate of 0.093 kg/m-s, the liquid films failed to fully enfold the tube surface with the appearance of dry areas, causing the substantial decline of heat transfer effectiveness. The condition at a high liquid flow rate of 0.186 kg/m-s achieved the average heat transfer coefficient up to 4.18 kW/m2 K, indicating good thermal performance similar to literature reports. Reasonable average heat transfer coefficients can be attained for the variation of dispensed angle within 30°.

Acoustic Nebulizer for the Processing of Undersized Fruit Plantations: Parameters and Operating Modes

When protecting undersized fruit plantations from diseases and pests, a large amount of working fluid is consumed, ordinary processing of fruit plantations reduces the productivity of sprayers. To solve this problem, it is proposed to use acoustic sprayers having a low liquid flow rate and a high degree of crushing. Studies have been carried out that have made it possible to optimize the parameters and operating modes of the acoustic sprayer and to establish a scheme for placing the sprayers on a sprayer. The dependence of the radius of the spray pattern on the design parameters of the nebulizer is found out. The average droplet diameter and the degree of coverage of the leaf surface are determined. The parameters of the proposed acoustic sprayer satisfy the agrotechnical requirements. The use of the proposed acoustic sprayer in the technological process of protecting undersized fruit plants allows to reduce the consumption of working fluid and to increase the productivity of the sprayer.

Study of primary instability of thick liquid films under strong gas shear

The initial stage of downward co-current annular flow was studied using two optical techniques: brightness-based laser-induced fluorescence technique and shadow technique. The experiments were conducted in a circular pipe and in a rectangular duct. The working area was represented by the first few centimetres from liquid inlet; the latter was organised as a tangential slot. The process of formation of disturbance waves was found to consist of three stages: formation of regular initial two-dimensional high-frequency waves; fragmentation into localised irregular three-dimensional waves and formation of large-scale quasi-two-dimensional disturbance waves. All the stages occur closer to the inlet at higher gas velocities and lower liquid flow rates. It was found that the initial two-dimensional waves appear at the initial area of thick film in the vicinity of the inlet. Spatiotemporal measurements were conducted and spectral and statistical approaches were applied to study the characteristics of the initial waves at the linear growth stage. The obtained characteristics were compared to the linear stability calculations; the comparison showed satisfactory agreement for the frequencies and velocities of the initial waves after taking into account non-equilibrium film thickness at the inlet.

Gas phase dispersion/mixing investigation in a representative geometry of gas-liquid upflow Moving Bed Hydrotreater Reactor (MBR) using developed gas tracer technique and method based on convolution/regression

Gas dispersion studies has been executed for the catalyst bed section of a representative geometry of scaled-down industrial Moving Bed Hydrotreater Reactor (MBR). The catalyst bed of MBR is modeled using Axial Dispersion Model (ADM) and its parameters gas dispersion coefficient (Dg) and Peclet number (Pe) are estimated using Residence Time Distribution (RTD) and implementing a methodology based on convolution and regression. Additionally, dimensionless variance (σD2) for the catalyst bed is also measured using RTDs first and second moments to compare with those findings of ADM model. This study is conducted at the varying flow rates of gas and liquid including scaled down operating conditions. The results of Dg,Pe, and σD2 indicate that bed behaves as a packed bed for low liquid flow rate and moves towards three-phase fluidized bed for increasing liquid flow rate. Overall the gas phase behavior is seen to be in plug flow for all the operating conditions, with relatively high dispersion/mixing in packed bed state. Scaled down flow conditions is seen to be best in terms of gas dispersion/mixing and catalyst utilization.

On the use of 3D-printed flow distributors to control particle movement in a fluidized bed

3D-printing has emerged as a revolutionary tool for the rapid-prototyping of both conventional and novel products. Its use can foster innovative solutions to engineering challenges that previously would have been considered impractical. We propose the manipulation and control of multiphase systems (e.g. fluidized bed bioreactors) as one such use. The article presented investigates the particle flow and mixing within a fluidized bed induced by novel additive manufactured flow distributors. The fluidized bed is designed for adherent cell expansion on 3mm diameter calcium alginate macrocarriers. Particle tracking was employed to assess the influence of flow channel angle and direction upon the radial flux of the carriers within the vessel. Uni-directional angled (45°) flow channels generated swirling fluidization of the macrocarriers; increasing particle radial velocities by up to 5.2 times (compared to their vertical flow channel counterparts) at a liquid superficial velocity of 0.0047m/s. Swirling fluidization also generated particle bed heights up to 52% higher than vertical flow channels. Bi-directional flow channels improved the spatial uniformity of particle radial velocity. In addition, the angular flow channels generated axial velocity gradients that facilitate fluctuations in the height of fluidized particles, thus counteracting elutriation. Finally, lower liquid flow rates and interstitial velocities were required to mix the particles, thus leading to lower hydrodynamic stresses introduced into the system. The introduction of multi-directional flow channels provides novel options to the design and use of flow distributor technology. We foresee additional advancements in chemical engineering product design utilizing additive manufacturing to manipulate multiphase flows.

Gravimetric system using high-speed double switching valves for low liquid flow rates

This paper presents a gravimetric system developed to perform the static weighing with flying-start-and-stop (SW-FSS) calibration method at low liquid flow rates using a pair of identical high-speed switching valves as a flow diverter. Features of the gravimetric system comprise three main components: a pair of switching valves that divert the working liquid between two symmetrical flow paths; a weighing vessel equipped with an overflow inner vessel and enclosed in a weighing chamber; and a liquid discharge mechanism comprising a discharge tube and a discharge pump, used with a multi-purpose bin. These are described with an explanation of the design considerations behind each feature. The overflow inner vessel is designed with a notch in its wall and is positioned so that it does not come into contact with the liquid surface of the accumulated liquid in the weighing vessel or the side wall of the weighing vessel to obtain a good repeatability of the interactive effects between the feeding tube and the submerging working liquid, thus ensuring a correct mass reading of the liquid collection. A performance test showed that, in terms of contribution to the overall uncertainty of the standard flow rate, the pair of switching valves is capable of performing SW-FSS satisfactorily with small relative timing errors within %. However, the mass loss due to evaporation is considered a major source of error of the gravimetric system, showing a maximum error of 0.011% under the most evaporative condition tested for the longest liquid collection time of the gravimetric system.

High-Precision Measurements and Regulation for Low Liquid Flow Rates

We develop a device for high-precision measurements and regulation of low flow rates of special liquids with different properties. The application of this device enables one to automate the process of high-precision mixing and dosing of various liquids with a possibility of control of the process of dosing in real time.

Effect of Bottom Baffles and Air Inlet Position on Mass Transfer Performance of a Water-Sparged Aerocyclone

Water-sparged Aerocyclone (WSA) is a new type of gas-liquid mass transfer equipment with a coupling field of liquid jet with gas cyclone, which can be widely used in wastewater treatment process. To further optimize the structural design of WSA, the effect of bottom baffles and air inlet position on mass transfer performance of WSA was comparatively studied by air stripping of ammonia from wastewater. The results indicated that the separation space configuration of a WSA affects its mass transfer performances. Under the same condition, the axial air inlet position has no effect on mass transfer performance, but moving air inlet position downward could reduce the gas pressure drop in WSA by about 10%, which was probably caused by abating the friction loss between the gas cyclone and the wall. In case of high air inlet velocity and low liquid flow rate, the bottom baffles in the WSA could intensify the mixing effect between gas and liquid phases, thereby improving the mass transfer performance, and the effect is more pronounced with the increase of air inlet velocity. The results could be used as a guide for the design of WSA with excellent mass transfer performance.

Ceramic membrane ozonator for soluble organics removal from produced water

In this work, the performance of ozonation for degradation of soluble organic compounds in produced water was investigated. Tubular ceramic membrane diffuser (with and without a static mixer in the lumen side) was used to facilitate contact between ozone and produced water. The ozonation was conducted at ozone flow rate of 8 L.min-1, ozone concentration of 0.4 ppm, original pH of the solution, and pressure of 1.2 bar, while the flow rates of the produced water were varied (192, 378 and 830 mL.min-1). It was found that the reduction of benzene, toluene, ethylbenzene, and xylene were 85%, 99%, 85%, and 95%, respectively. A lower liquid flow rate in a laminar state showed a better component reduction due to the longer contacting time between the liquid and the gas phase. The introduction of the static mixer in the lumen side of the membrane as a turbulence promoter provided a positive effect on the performance of the membrane diffuser. The twisted static mixer exhibited the better removal rate than the spiral static mixer.

Experimental and computational investigations on severe slugging in a catenary riser

Severe slugging can occur in a pipeline-riser system at relatively low liquid and gas flow rates during gas-oil transportation, possibly causing unexpected damage to the production facilities. Experiments with air and water are conducted in a horizontal and downward inclined pipeline followed by a catenary riser in order to investigate the mechanism and characteristics of severe slugging. A theoretical model is introduced to compare with the experiments. The results show that the formation mechanism of severe slugging in a catenary riser is different from that in a vertical riser due to the riser geometry and five flow patterns are obtained and analyzed. A gas-liquid mixture slug stage is observed at the beginning of one cycle of severe slugging, which is seldom noticed in previous studies. Based on both experiments and computations, the time period and variation of pressure amplitude of severe slugging are found closely related to the superficial gas velocity, implying that the gas velocity significantly influences the flow patterns in our experiments. Moreover, good agreements between the experimental data and the numerical results are shown in the stability curve and flow regime map, which can be a possible reference for design in an offshore oil-production system.

Characterization of 3-D wave flow regimes on falling liquid films

Experimental study of wave evolution on the surface of isothermal liquid films falling down vertical plate conducted by means of field measuring system has revealed three typical scenarios of the evolution in the range of low and moderate liquid flow rates. At low liquid flow rates transverse modulation of 2D waves develops without formation of 3D waves. Two dimensional waves break up into 3D waves only when Reynolds number Re of the film flow exceeds some threshold value which depends on physical properties of working fluid. The fully developed steady-state 3D wave regimes are observed when Re exceeds another threshold value. The obtained results allow to determine the boundaries within which the adequate comparison between modeling and experiments on 3D wave flow of liquid films is possible.

Quantitative analysis of transverse non-uniformity of liquid film at the initial stage of annular-dispersed flow

The process of formation of disturbance waves in annular gas-liquid flow was studied using three-dimensional configuration of brightness-based laser-induced fluorescence technique in two ducts of different geometry in the proximity of the inlet. The process was found to consist of three stages: formation of initial two-dimensional high-frequency waves; fragmentation into localised chaotic 3D-waves and formation of large-scale quasi-2D disturbance waves. A method of quantitative characterisation of the degree of transverse coherence of film surface was developed and used to estimate the coordinates of the borders of the three stages. All the stages occur closer to the inlet at higher superficial gas velocities and lower liquid flow rates. It was found that the shape of the duct does not exert significant influence of the distance of existence of two-dimensional initial waves, whilst the disturbance waves are formed closer to the inlet in the circular duct.

Study of development of disturbance waves in annular gas-liquid flow

Downstream development of disturbance waves properties in annular regime of gas - liquid flow was conducted in adiabatic air-water downwards flow in a vertical pipe with inner diameter of 11.7 mm. The measurements were conducted using brightness-based laser-induced fluorescence technique. Instantaneous distributions of local thickness of liquid film along one longitudinal section of the duct over the first 45 cm from the inlet were obtained with sampling frequency of 10 kHz. Based on these spatiotemporal plots, dependence of local average velocity of disturbance waves on downstream distance was obtained for a wide range of gas and liquid flow rates. Three main stages of flow development were identified: a stage prior to formation of disturbance waves, a stage of constant acceleration of disturbance waves and a stage of deceleration nearly compensating the initial acceleration. Transitions to both second and third stages occur closer to the inlet at higher gas velocities and lower liquid flow rates. The initial acceleration is defined by the effect of the gas shear; it grows in parabolic manner with superficial gas velocity and shows weak dependence on liquid flow rate. The deceleration is supposed to occur due to entrainment of liquid from disturbance waves.

Development of a gravimetric system using a conical rotating double-wing diverter for low liquid flow rates

An improved gravimetric system for low flow rates was developed at National Metrology Institute of Japan (NMIJ) to perform calibration method of flying-start-and-stop. The present paper describes the main features of the gravimetric system comprising three main components – a compact and umbrella-like conical rotating double-wing diverter, a weighing tank with a chimney-like inlet structure, and a liquid discharge mechanism using a suction nozzle – with explanation of the design considerations behind each feature. Performance tests show that, under the most unfavorable conditions, diverter timing error relative to liquid collection time is below 0.003% whereas evaporation rate of weighing tank relative to amount of liquid collection is below 0.005%. Dependency of diverter timing error on flow rates due to liquid collection loss was also revealed, and this shortcoming was improved by either one of the two following countermeasures: adjustment of nozzle sizes or modification of wing shape. These two measures are both effective in achieving a consistent timing error with varying flow rates. The overall performance results confirm the gravimetric system's capability in performing low flow calibration.

The effect of mesh-type bubble breaker on two-phase vertical co-flow

The influence of a mesh-type bubble breaker in a two-phase vertical co-flow is experimentally investigated using high-speed imaging. A range of liquid and gas flow rates were considered that correspond to the gas-to-liquid flow rates ratios (GLRs) from 0.05 to 39.6 covering bubbly, slug and churn flow regimes. The mesh-type bubble breaker was found to be effective in reducing the size of nozzle-generated bubbles in two-phase co-current vertical flow. The bubble size reduction by 50%-70% is observed in the presence of the mesh-type bubble breaker compared to that without a bubble breaker. The results also show that at a given GLR, the mesh-type bubble breaker delayed the flow regime transition compared to that without a bubble breaker. A Froude number correlation was proposed to predict the mean bubble size downstream of the bubble breaker for the bubbly flow regime, which accurately predicted the bubble size over a range of bubble breaker parameters. It is observed that the geometry of the bubble breaker influence the two-phase flow regime transition. At low liquid flow rates, small pore size of the breaker was found to be effective. This effect diminishes at higher liquid flow rate due to the elongation of the bubbles by the liquid inertia. The results also show that a longer bubble breaker located closer to the bubble generating nozzle is the most effective in producing bubbly flow over a longer range of gas-liquid flowrates ratios.

Comparison of a high temperature torch integrated sample introduction system with a desolvation system for the analysis of microsamples through inductively coupled plasma mass spectrometry

This work describes for the first time the comparison of the analytical performances obtained with a high temperature torch integrated sample introduction system (hTISIS) against those found with a commercially available desolvation system (APEX) associated with inductively coupled plasma mass spectrometry (ICP-MS). A double pass spray chamber was taken as the reference system. Similar detection limits and sensitivities were obtained in continuous injection mode at low liquid flow rates for the APEX and hTISIS operating at high temperatures. In contrast, in the air-segmented injection mode, the detection limits obtained with hTISIS at high temperatures were up to 12 times lower than those found for the APEX. Regarding memory effects, wash out times were shorter in continuous mode and peaks were narrower in air segmented mode for the hTISIS as compared to the APEX. Non spectral interferences (matrix effects) were studied with 10% nitric acid, 2% methanol, for an ICP multielemental solution and a hydro-organic matrix containing 70% (v/v) acetonitrile in water, 15mmolL−1 ammonium acetate and 0.5% formic acid containing lanthanide complexes. In all the cases, matrix effects were less severe for the hTISIS operating at 200°C and the APEX than for the double pass spray chamber. Finally, two spiked reference materials (sea water and Antartic krill) were analyzed. The hTISIS operating at 200°C gave the best results compared to those obtained with the APEX and the double pass spray chamber. In conclusion, despite the simplicity of the hTISIS, it provided, at low liquid flow rates, results similar to or better than those obtained with the by other sample introduction systems.

Enhancing Capillary-Driven Flow for Paper-Based Microfluidic Channels.

Paper-based microfluidic devices have received considerable interest due to their benefits with regards to low manufacturing costs, simplicity, and the wide scope of applications. However, limitations including sample retention in paper matrix and evaporation as well as low liquid flow rates have often been overlooked. This paper presents a paper-based capillary-driven flow system that speeds up flow rates by utilizing narrow gap geometry between two parallel surfaces separated by a spacer. The top surface is hydrophobic, while the bottom surface is a hydrophobic paper substrate with a microfluidic channel defined by a hydrophilic pathway, leaving sides of the channel open to air. The liquid flows on the hydrophilic path in the gap without spreading onto the hydrophobic regions. The closed-channel flow system showed higher spreading distances and accelerated liquid flow. An average flow rate increases of 200 and 100% were obtained for the nanoparticle-coated paperboard and the blotting papers used, respectively. Fast liquid delivery to detection zones or reaction implies rapid results from analytical devices. In addition, liquid drying and evaporation can be reduced in the proposed closed-channel system.

Hydrodynamics in falling liquid films on surfaces with complex geometry

These studies include investigation of the character of liquid spreading over the surfaces with complex geometry, the effect of microstructure, corrugation angle, and perforation on the wave film flow. The paper present the results of experimental studies on dynamics of the film flow of cryogenic liquid over the complex surfaces: vertical plane and ribbed aluminum plates with/without wave microtexture. Experimental results were obtained at the flow of liquid nitrogen.According to results of experiments on the ribbed structured perforated aluminum surfaces with the use of highly wetting low-viscous liquids, the film flow character depends significantly on the irrigation rate. The direction and parameters of microstructure, the angle of inclination of the main fins, position and diameter of holes effect significantly the zones of liquid spreading and its distribution over the surface of the ribbed structured plates, especially, within the range of low liquid flow rates. According to high-speed video recording, in case of horizontal microstructure the wave dynamics influences considerably liquid redistribution in transverse direction. This is caused by the fact that liquid flows intensively at propagation of secondary waves along the channels of horizontal microstructure.Experimental results on dependence of the relative portion of liquid, held in a single irrigated channel of the corrugated plates with different thicknesses, on the irrigation degree are presented.