Effect Of Liquid Flow Rate Research Articles

CFD simulation of geometrical parameters effects on the hydrodynamic characteristics and CO2 absorption efficiency of Arc-RPB

The Computational Fluid Dynamics (CFD) technique was used to study the effect of the geometrical parameters on the intensification of hydrodynamic parameters and Carbon dioxide (CO2) absorption efficiency by Mono-Ethanol-Amine (MEA) solution in a novel Arc-blade Rotating Packed Bed reactor (Arc-RPB). The VOF multiphase approach and RNGk-ε turbulent model were used to study the multiphase and turbulent behavior of the flow field in the computational domain, respectively. The effects of liquid flow rate, the bed wire mesh diameter, and number of the mesh layers were studied on the liquid holdup (αL), gas-liquid interfacial area (Aint) and liquid dispersion index (Id). Considering the Arc-RPB bed wire mesh diameter from 0.2 mm to 1.6 mm showed that αL, Aint and Id decrease 20%, 29% and 11%, respectively. By examining the effect of the bed layers enhancement, the liquid holdup αL decreased by about 36% but, Aint and Id reached a maximum value at 16 bed layers. Finally, with study the effect of the bed geometrical parameters on CO2 absorption efficiency, results showed the efficiency reduces about 7.5% with increase in the bed mesh diameter and shows a maximum at 16 bed layers.

Experimental Study on Gas–Liquid Performance and Prediction of Shaft Power and Efficiency by Dimensionless Coefficients in a Multistage Electrical Submersible Pump

AbstractElectrical submersible pumps (ESPs) widely used in oil-gas artificial lift consume a lot of electric energy in long-term operation. This paper mainly focuses on the gas–liquid performance and predicting shaft power and efficiency of a 25-stage ESP. First, the calculation methods of two-phase hydraulic parameters and corresponding dimensionless hydraulic coefficients based on isothermal compression are proposed. Ignoring the gas compressibility will result in large errors in calculating two-phase hydraulic parameters. Then, the effects of liquid flowrate, inlet gas volume fraction, and rotational speed on head, shaft power, and efficiency are analyzed. The severe two-phase head degradation disappears in downstream stages of the ESP because of the decreasing interstage gas volume fraction. Similar to the head, the shaft power and efficiency decrease slowly at first, then rapidly, and finally slowly with the increase of inlet gas volume fraction. Finally, correlations are proposed for predicting the shaft power and efficiency by the dimensionless head and flow coefficients. There is a power function relation between two-phase head coefficient and efficiency. Thus, through the pump head which can be easily acquired by differential pressure signals in pipeline, prediction correlations for shaft power and efficiency are established with the relative errors lower than 10%. The prediction method based on two-phase dimensionless coefficients can also be referenced to ESPs with different types.

Experimental Study on Bubble Entrainment by a Free Fall Jet in an Argon‐Filled Continuous Casting Tundish

Inert gas entrainment by the impact of free fall jet can avoid the bubble grow‐up on nonwetting interface between liquid steel and refractory gas nozzle, which produces bubbles as small as 0.37 mm for deep cleaning the liquid steel in an argon‐filled tundish. The time‐dependent vibration of free fall jet is described by a high‐speed camera combined with image postprocessing software. The effect of liquid flow rate and free fall length on jet vibration is investigated. The equivalent surface roughness is proposed to characterize the surface wave of free fall jet without fixed amplitude and frequency. The entrained gas flow rate shows a good correlation with the equivalent surface roughness. Gas entrainment cannot happen with a free fall jet shorter than 2 mm, as the jet vibration is insufficient to make the bubbles separate from the gas sheath. The surface fluctuation caused by the impact of free fall jet can be well isolated within a submerged shield that remains a stable slag layer outside of the shield. Besides, the strong mixing flow caused by free fall jet is beneficial to dissipate the turbulence kinetic energy of the entry flow, which improves the tundish flow field.

Optofluidic microreactor for the photocatalytic water splitting to produce green hydrogen

The microfluidic devices can effectively be used for the renewable energy conversion, such as solar to chemical (e.g., H2) energy, to meet the global energy demand. The microchannel design plays a vital role in improving the mass transfer in photocatalytic processes. In this study, a simple, rapid, and inexpensive adhesive tape-based method was used to fabricate the serpentine, planar and micropillared optofluidic microreactors with sharp edges without any wall irregularities. The sol-gel method was used for the CdS catalyst coating in the microreactors. The effect of liquid flow rate (0.05–1 mL min−1) and sacrificial reagent (Na2SO3/Na2S) concentration (0.05–0.5 M) on the hydrogen generation under visible light was studied. A higher H2 production rate was observed in the serpentine microreactor as compared to that in planar and micropillared microreactors. The serpentine microreactor, having higher surface-to-volume ratio, induced the micromixing that enhanced the mass transfer of the sacrificial reagent and formed H2 gas. A maximum H2 production rate of 2.65 μmol h−1 cm−2 was observed at a flow rate of 1.0 mL min−1 and a sacrificial reagent concentration (Na2SO3/Na2S) of 0.5 M. The new approach developed in this study is a step forward in fabricating highly efficient and inexpensive optofluidic microdevices for the hydrogen production from solar energy.

Adsorption of Tartrazine anionic dye by novel fixed bed Core-Shell- polystyrene Divinylbenzene/Magnetite nanocomposite

In this study, the in situ chemical polymerization process was used to synthesize polystyrene/magnetite nanocomposite (PS-DVB/ Fe3O4). The prepared composite was characterized by XPS, SEM, XRD, HRTEM, FT-IR, and TGA technique. The XPS as an essential elemental analysis tool proved the proposed general formulae of the prepared nanocomposite (PS-DVB/ Fe3O4). FT-IR data proved the functional groups in the proposed structural formula of the prepared nanomaterials. The thermal analysis confirmed the high thermal stability of the prepared core–shell polymer. XRD results prove the crystallinity and single phase. Scanning electron microscope (SEM) and the presence of Fe2O3 and PS-DVB/Fe3O4 composite has been confirmed by HRTEM. The particle size analysis was used to determine the distribution of particle size within the polymer matrix. The adsorption potential of Tartrazine azo dye from polluted water samples onto cross-linked (PS-DVB/Fe3O4) using fixed-bed adsorption column was investigated. The adsorption capacity of Tartrazine onto PS-DVB greatly improved when Fe3O4 is added to the porous composite of PS-DVB copolymer to be 0.15 mol with removal efficiency reach 98%. In this respect, the effect of liquid flow rate, initial Tartrazine concentration, and PS-DVB/Fe3O4 bed height on the adsorption technique's breakthrough features was taken. In this work, the mass transfer model, which involved the two parameters of τ (50% breakthrough time) and k (adsorption rate constant), was suggested for discussion the effect of PS-DVB/Fe3O4on such values. It was found that the adsorption capacity Qe and τ values were decreased with the flow rate increases. The flow rate had little effect, at least for the PS-DVB/Fe3O4, on the k value. On the other hand, both Qe and τ values decreased with increasing the initial Tartrazine concentration, whereas the k value was slightly increased. We concluded that the liquid flow rate, initial Tartrazine concentration, and bed height were1mL/min, 5 M, and 7 cm, respectively. Finally, the PS-DVB/Fe3O4 was a suitable Tartrazine adsorbent using a fixed-bed adsorption column, which fitted well with the mass transfer model.

Rapid degradation of refractory organic pollutants by continuous ozonation in a micro-packed bed reactor

Recently microreactor technology attracts attention due to the excellent multiphase mixing and enhanced mass transfer. Herein, a continuous ozonation system based on a micro-packed bed reactor (μPBR) was used to improve the dissolution rate of ozone and achieved a rapid and efficient degradation of refractory organic pollutants. The effects of liquid flow rate, gas flow rate, initial pH, initial O3 concentration and initial phenol concentration on the phenol and chemical oxygen demand (COD) removal efficiencies were also investigated. Experimental results showed that phenol and COD removal efficiencies under optimal conditions achieved 100.0% and 86.4%, respectively. Compared with large-scale reactors, the apparent reaction rate constant in μPBR increased by 1-2 orders of magnitude. In addition, some typical organic pollutants (including phenols, antibiotics and dyes) were treated by ozonation in μPBR. The removal efficiencies of these organic pollutants and COD achieved 100.0% and 70.2%–80.5% within 71 s, respectively. In this continuous treatment system, 100% of the unreacted ozone was converted to oxygen, which promoted the healthy development of aquatic ecosystems. Thus, this continuous system based on μPBR is a promising method in rapid and efficient treating refractory organic pollutants.

Preparation of silk fibroin-based microspheres under high-gravity field

The possibility of preparing regenerated silk fibroin (RSF)-based microspheres by a high-gravity anti-solvent precipitation method was explored. The high-gravity environment was generated by a rotating packed bed (RPB) reactor. Aqueous RSF solutions and ethanol were used as solvent and anti-solvent, respectively. The effects of liquid flow rates and anti-solvent/solvent ratios, as well as centrifugation and freezing time, on the formation, size distribution and morphology of RSF microspheres were investigated. The results showed that RSF microspheres, with diameters of 0.1–1.6 μm, can be prepared under high-gravity field via self-assembly of RSF molecular chains induced by ethanol and quenched by freezing and lyophilization. The mechanism of RSF microsphere formation was also discussed. In addition, rhodamine B was used as a model drug for evaluation of drug delivery capability of the RSF microspheres. The merits of this study lie in a simple low-cost apparatus with ease for scale-up and thereby potential high volume continuous production capacity, which is of practical advantages and industrial significance in preparation of protein microspheres for commercial mass production.

Formation and uniformity of bubbles in highly viscous fluids in symmetric parallel microchannels

This work focuses on the formation and uniformity of bubbles in highly viscous fluids in symmetric parallel microchannels by using a high-speed camera. Nitrogen and high viscous glycerol-water solution containing 0.3% SDS are used as the gas and liquid phases respectively. The interface evolution during bubble information is reported. The effects of liquid flow rates, liquid viscosities, gas pressures, and microchannel configurations on bubble size distribution are investigated based on the gas-liquid two-phase flow resistance model. It is found that the difference in the downstream resistance, the pressure fluctuation of the upstream channels, and the feedback effect of bubble behaviors in the cavity affect the uniformity of bubble size. In the configuration that the widths of the microchannels engineered according to Murray's law, the uniformity is better, under low gas pressures, high viscosities and flow rates of liquids. Finally, the prediction models of bubble size in both geometries are proposed.

Enhanced Spray Cooling Using Micropillar Arrays: A Systematic Study

Abstract The role of contact-line evaporation on spray impingement heat transfer is systematically studied by spraying de-ionized water on silicon substrates with micropillar arrays. The height, the pillar diameter, and the spacing of the micropillar array were varied from 5 to 50 μm while keeping the porosity constant at 0.75. An air-assisted nozzle was used to create a liquid spray with a Sauter mean diameter (SMD) of ∼22 to 42 μm depending on flow conditions. Most test runs were conducted at a water flow rate of 30 ml/min and an air-liquid mass flow rate ratio of ∼0.57. The results show a continuous increase in the critical heat flux (CHF) as the pillar diameter is decreased. The effects of pillar height are nonmonotonic, with CHF and peak heat transfer coefficient attaining a maximum as the height-to-diameter ratio approaches unity. Values of CHF as high as 830 W/cm2 were achieved, along with cooling efficiencies of 49%. The effect of liquid flow rates and air-flow rates were also investigated independently using textured surfaces.

Hydrodynamics and phenol adsorption studies in continuous counter current liquid-solid settling column

Adsorption is a cost-efficient and a well-established method to treat a large volume of wastewater. Most of the adsorption studies have been carried out in batch and continuous (packed and fluidized bed column) reactors. In most of the continuous operations, a solid adsorbent is held in batch mode and the liquid phase is continuous. In a counter-current liquid-solid adsorber, both the liquid and solid phase will be continuous. In this study, synthetic wastewater containing phenol of 200 ppm is treated in a counter-current liquid-solid adsorber using activated carbon as the adsorbent. The adsorption kinetics and the effect of size and mass of adsorbent were studied in batch operation. Thermodynamic properties including Gibbs' free energy, standard enthalpy and entropy change were calculated and the feasibility of the process is confirmed. In the continuous counter-current liquid-solid settling column, the effects of liquid flow rate, particle size and solid flow rate on hydrodynamics and mass transfer have been studied. From the range of flow rates studied in this work, liquid flowrate of 10 lph and solids (of diameter 0.5 mm) flow rate of 24 g/s gave the maximum phenol removal. An empirical equation has been proposed to predict the mass transfer coefficient for the range of continuous process.

Effect of Liquid Flow Rate on Carbon Dioxide Absorption Performance Using Aqueous Potassium Carbonate Promoted with Glycine at Elevated Pressure Condition of Packed Absorption Column

This paper presented the absorption removal efficiency for carbon dioxide (CO2) removal from natural gas using an environmental friendly solvent, potassium carbonate promoted with glycine. Recently, CO2 capture using this solvent (with precipitating) was studied by previous researchers. However, the precipitates of the solvent increase the potential of blockage in the packing and piping thus result failure in absorption processes. Therefore, this study focused to assess the CO2 removal efficiency of non-precipitating potassium carbonate promoted with glycine. This green solvent contains aqueous blend of 20 wt% potassium carbonate and 8 wt% glycine. The absorption performance of the solvent was obtained by demonstrated a few experimental works using a bench scale packed absorption column. The packing type was Sulzer metal gauze and the column consisted of six sampling point which located equidistance along the packing. The effect of liquid flow rate was assessed in term of its CO2 removal efficiency and concentration profile along the packing. The study shows the increasing trend of CO2 removal as liquid flow rate increases. Higher liquid/molar flow rate gas (L/G) offers a better absorption performance compared to lower L/G ratio. The results demonstrated the efficient absorption up to 77% using non-precipitating potassium carbonate promoted with glycine.

Fast screening of amine/physical solvent systems and mass transfer studies on efficient aqueous hybrid MEA/Sulfolane solution for postcombustion CO2 capture

AbstractBACKGROUNDThe addition of a physical solvent to a traditional chemical absorbent has been shown to improve the absorption and desorption performance of the absorbent system. This type of novel absorbent system combining a single physical solvent with an amine solvent is a promising development in the industrial application of CO2 capture.RESULTSHybrid solutions composed of Monoethanolamine (MEA), a physical solvent, and H2O were comprehensively investigated using the rapid solvent screening apparatus and a VLE apparatus. The results show that 30 wt% MEA with 20 wt% Sulfolane and 50 wt% H2O achieved higher rich loading, strong cyclic CO2 capacity and the highest desorption rate over a wide range of CO2 loadings. Also, the mass transfer performance of CO2 absorption into the 30 wt% MEA and 20 wt% Sulfolane solution was investigated in a lab‐scale random packing column. The effects of liquid flow rate, liquid feed temperature, lean CO2 loading, inert gas flow rate and CO2 partial pressure on the mass transfer performance were evaluated in terms of volumetric overall mass transfer coefficient (KGav). Furthermore, a correlation was developed for CO2 absorption into MEA/Sulfolane solution in a random packing column using semi‐empirical models as functions.CONCLUSIONUnlike for amine solution alone, inert gas flow rate is an indispensable operating parameter in the MEA/Sulfolane system. A mass transfer correlation model was established and holds significance in studying the kinetics of CO2 absorption by a mixture of physical and chemical solvents and for the optimal design of Dixon‐ring random packing columns. © 2019 Society of Chemical Industry

Study on the formation characteristic of microbubbles used in sewage treatment

Microbubble usually has very small volume, and it is difficult to rise in the water, so it can be used to wrap ozone for sewage treatment. In the present study, the experiments of bubble formation in a mechanical microfluidic device are developed. The effect of liquid flow rate and gas pressure on bubble formation characteristic was obtained through experiments. By observing experimental phenomena, it can be concluded that bubble growth process can be divided into three stages, and the law of the detachment volume and formation frequency of microbubbles under single variable factor was investigated by the control variable method. The investigation of bubble formation characteristic can help to control bubble detachment volume and formation frequency precisely.

Growth Characteristic of Microbubble in a Co-flowing Liquid in Microfluidic Chip

Experiments of microbubble formation in a co-flowing liquid in polydimethylsiloxane (PDMS) microfluidic chip were developed. The experimental system was set up to investigate the effects of liquid flow rate, gas pressure, gas channel width and concentration of polyvinyl alcohol (PVA) solution on microbubble growth process. Three stages of the bubble growth process were first obtained through experiments. The control variable method was used to explore the growth characteristics of bubbles, such as the volume change rate, the contact angle, the ratio of length to width, and the centroid displacement. This study provides an empirical reference for the growth process of microbubbles in microfluidic chips, which helps to achieve precise control of microbubble volume and generation frequency.

Effect of Activated Alkanolamine for CO2 Absorption using Hollow Fiber Membrane Contactor

Hollow Fiber Membrane Contactor (HFMC) technology has been widely developed as an alternative technology to separate CO2 gas. HFMC technology combines gas absorption process with absorbent and membrane technology. Membrane contactor technology has advantages than conventional technology such as larger gas-liquid contact area, smaller equipment, modularity, and gas-liquid flow rates adjusted independently. In this research, the CO2 absorption experiments was conducted for absorption process at 30°C temperature and various gas flow rate from 200 - 600 mL/min, feed gas of CO2 20%vol. flowed into shell side and the absorbents flowed in tube side of membrane contactor. Piperazine (PZ) and monosodium glutamate (MSG) as activators with 1%w/w concentration, added into methyldiethanolamine (MDEA) 30% w/w solution to form aqueous solutions of activated MDEA. The membrane material used in this experiment was hydrophobic polypropylene membrane. The effect of liquid flow rate and various activators used to get CO2 absorption flux and CO2 removal in HFMC. The results showed that the best of CO2 absorption process using activated alkanolamine was MDEA-PZ, where the highest flux value was 5.5x10−4 mole/m2.s and CO2 removal reached 96.9% at a gas flow rate of 600mL/min.

Microbubble characteristic in a co-flowing liquid in microfluidic chip

An experimental method for the formation characteristics of co-flowing focusing microbubbles based on polydimethylsiloxane (PDMS) microfluidic chip is introduced. An experimental system was set up to investigate the effects of liquid flow rate, gas pressure and gas channel width on bubble detachment volume and formation time. Based on the assumption of ellipsoid theory, the theoretical model for volume prediction of co-flowing focusing microbubbles is established. The numerical solution of the model is obtained by the fourth-order Runge-Kutta method. The results show that the prediction results of theoretical model correlate well with the experimental data.

Growth characteristic of microbubble in a T-junction microchannel in microfluidic chip

Microbubble formation in a T-junction microchannel in polydimethylsiloxane (PDMS) microfluidic chip were developed. The experiment based on high-speed microscopic camera system was set up to investigate the effects of liquid flow rate, gas pressure and gas channel width on microbubble growth. Three stages of microbubble growth process were obtained through the experiment firstly. The control variable method was used for investigating the growth characteristics of microbubble, including volume change rate and the ratio of length to width. The present study provided an empirical reference for the growth of microbubble in microchannel, which helped to achieve precise control of microbubble volume.

CO2 REMOVAL EFFICIENCY FROM NATURAL GAS AT ELEVATED PRESSURE OF PACKED ABSORPTION COLUMN USING POTASSIUM CARBONATE PROMOTED WITH GLYCINE

This article reports the absorption removal efficiency for carbon dioxide (CO2) capture from natural gas using an environmental friendly solvent, potassium carbonate promoted with glycine. Recently, CO2 capture using this solvent (with precipitating) was studied by previous researchers. However, the precipitates of the solvent increase the potential of blockage in the packing and piping thus result failure in absorption processes. Therefore, this study focused to assess the CO2 removal efficiency of non-precipitating potassium carbonate promoted with glycine. This green solvent contains aqueous blend of 20 wt% potassium carbonate and 8 wt% glycine. The absorption performance of the solvent was obtained by demonstrated a few experimental works using a bench scale packed absorption column. The packing type was Sulzer metal gauze and the column consisted of six sampling point which located equidistance along the packing The system was running over a range of liquid flow rate 1.81-7.22 m3/m2.h at fixed operating pressure (4 Mpa), CO2 inlet concentration (20%), gas flow rate (33 kmol/m2.h) and solvent temperature (60 . The effect of liquid flow rate was assessed in term of its CO2 removal efficiency and concentration profile along the packing. The study shows the increasing trend of CO2 removal as liquid flow rate increases. Higher liquid/molar flow rate gas (L/G) offers a better absorption performance compared to lower L/G ratio. This study demonstrated the efficient absorption up to 77 % using non-precipitating potassium carbonate promoted with glycine.

Microbubble characteristic in a T-junction microchannel in microfluidic chip

ABSTRACTFormation characteristic of microbubble in a T-junction microchannel in polydimethylsiloxane (PDMS) microfluidic chip is investigated. Microbubble formation experiments are carried out to investigate the effects of liquid flow rate, gas pressure and gas channel width on the detachment volume and formation time of microbubble. The growth process of the bubble is described by the form of force analysis, and the definition of the bubble detachment distance is introduced. The equivalent spherical theoretical model of bubble detachment diameter prediction is established, and the numerical solution of the model is obtained by the fourth-order Runge–Kutta method. The prediction results of theoretical model correlate well with the experimental data.

Experimental investigation of heat transfer in a rivulet driven by gas flow in a minichannel

The heat transfer in a shear driven rivulet flow at isothermal conditions in a minichannel has been studied. The experiments were conducted using the setup, specially designed for the shear driven rivulet flow. The effect of liquid flow rate and substrate temperature on the width of the rivulet was studied experimentally using Laser induced fluorescence technique (LIF). The temperature distribution for different time moments of the rivulet surface was measured by the FLIR infrared (IR) camera. IR-measurements served to demonstrate that rivulet surface temperature is lower than substrate one due to liquid evaporation from the rivulet surface.