Increasing Liquid Flow Rate Research Articles

Process modeling and optimization of Rhodamine B dye ozonation in a novel microreactor equipped with high frequency ultrasound wave

This paper reports the effect of 1.7 MHz ultrasound wave on decolorization efficiency of Rhodamine B (RB) solution by ozone in a T-type microreactor. Response surface methodology using central composite design (CCD) was used for analysis and optimization of the reaction conditions. The effective parameters such as solution pH, dye initial concentration, liquid volumetric flow rate, ozone dosage and the length of microreactor on decolorization process were investigated. Rhodamine B removal from solution was determined in presence of and without sonication. The results indicate that for both modes, the decolorization efficiency of RB increased with increase of the ozone dosage as well as the length of employed microreactor. However, with increase of RB initial concentration and liquid flow rate, the decolorization efficiency was decreased. The comparison between the reactors with and without sonication shows that the application of ultrasound wave is effective more than 15% on removal efficiency of RB at various conditions. At optimum conditions, the experimental RB removal yield of 97. 3% and 95. 8 was obtained for with and without irradiation layouts, respectively. The statistical analyses and the agreement of the experimental results with model predictions showed the reliability of the regression model.

ECVT imaging and model analysis of the liquid distribution inside a horizontally installed passive cyclonic gas–liquid separator

Passive cyclonic gas–liquid separators (PCGLSs) have unique advantages compared with other types of gas–liquid separators. In this study, liquid distribution inside a horizontally installed PCGLS is investigated using electrical capacitance volume tomography (ECVT). The liquid distribution is measured under various gas and liquid flow rates. It is found that the inlet liquid flow rate is the dominating factor influencing the liquid distribution. The angular velocity of the liquid layer is found to be proportional to the liquid flow rate when no gas is injected. The center axis of the gas core is observed to be lower than the center axis of the separator cylinder, and it will drift towards the separator׳s center axis with increasing liquid flow rate. A mechanistic model is derived, and flow field parameters are solved analytically to qualitatively explain this phenomenon. The calculated gas core positions match the ECVT images well.

Effects of graphene oxide nanofluids on heat pipe performance and capillary limits

In the present study, thermal performances of water-filled and 0.01 and 0.03 vol% graphene oxide (GO)/water nanofluids-filled heat pipes with a screen mesh wick were studied in order to investigate the effects of nanofluids on the heat pipe operation. The wall temperatures of the GO/water nanofluids-filled heat pipes were found to be lower than those of the water heat pipe. Also, the heat pipes charged with GO/water nanofluids showed lower evaporator thermal resistances by about 25% compared with the water-filled heat pipe, although the condenser thermal resistances were similar in both cases. The 0.01 vol% GO/water nanofluid-filled heat pipe showed better boiling heat transfer than 0.03 vol% GO/water nanofluid because of the different structures of the deposited nanoparticle layers on the wicks. The capillary limit of the heat pipes containing GO/water nanofluids was higher than for the water heat pipe, because the nanoparticles-coated layer modified the effective capillary radius and meniscus, resulting in an increase of the maximum liquid flow rate through the wick structure. The SEM images and wetting properties for wicks of the heat pipes with nanoparticles-coated layers support the thermal performance characteristics of the heat pipes obtained in the study.

Effect of Air Humidification on the Pumping Efficiency of Water in a Packed Column Humidifier

The effects of water temperature on the discharged liquid flow rate, pumping efficiency, gas holdup and slip velocity were examined for an airlift pump with a riser filled with packing. Comparing with ordinary airlift pumps operating in ordinary conditions, the humidification of contributes positively in the increase of pumped water flow rate and saving energy.In this study, for the purpose of high pumping efficiency, several water temperatures were tested for many submersion ratios and gas flow rates. The results show that the increase of water temperature causes air humidification, gas holdup and high Reynolds number. Or the pumped liquid flow rate and slip velocity increase with the gas holdup growth. Therefore, the pumping efficiency will be higher with air humidification.

Effect of Liquid Flow Rate and Amine Concentration on CO<sub>2</sub> Removal from Natural Gas at High Pressure Operation in Packed Absorption Column

Greenhouse gas (GHG) emissions such as carbon dioxide (CO2) and methane (CH4) from oil and natural gas operation at offshore platforms have significant contribution to global warming. The reduction of these GHG emissions is possible through CO2 capture technology. This study reports the absorption performance of monoethanolamine (MEA) for the removal of CO2 from natural gas (NG) at high pressure conditions. The absorption experiments were performed in an absorption column packed with Sulzer Metal Gauze Packing at 5.0 MPa operating pressure. The absorption performance was evaluated in terms of CO2 removal (%) with liquid flow rate ranging from 1.81 to 4.51 m3/m2.h and MEA concentration of 1.0 - 4.0 kmol/m3. It was found that CO2 removal (%) had increased with increasing liquid flow rate and MEA concentration.

Mass transfer performance of rotating packed beds with blade packings in carbon dioxide absorption into sodium hydroxide solution

This study investigated the mass transfer performance of the rotating packed bed (RPB) with blade packings in carbon dioxide (CO2) absorption by sodium hydroxide (NaOH) solution. The overall volumetric gas-phase mass transfer coefficients (KGa) were compared using 1vol% CO2 and 1mol/L NaOH solution for three RPBs with blade packings with the effects of rotational speed, gas flow rate, and liquid flow rate. As expected, the rotational speed positively affected the KGa values for all RPBs. Furthermore, the obtained results indicated that the KGa values increased as the inner radius of the bed was increased and the outer radius of the bed was decreased. Moreover, the KGa values increased with an increasing liquid flow rate and an increasing gas flow rate for all RPBs. According to the comparison with the RPB with structured packings, the RPB with blade packings had applicability in removing CO2 from the exhaust gas.

Absorption of CO2 from natural gas using different amino acid salt solutions and regeneration using hollow fiber membrane contactors

Natural gas consists primarily of methane but it also contains considerable amounts of contaminating compounds mainly carbon dioxide (CO2). In the present work, the absorption/Stripping performance of four different amino acid salt (AAS) aqueous solutions was compared with MEA and NaOH solutions by using homemade PVDF hollow fiber gas–liquid membrane contactor modules. Compared to MEA, AAS have enhanced CO2 absorption/stripping performance. The experimental results show that the absorption performance can be enhanced by increasing liquid flow rate. However, the gas flow rate has negative effect on the removal efficiency although flux increases. Furthermore, it has been observed that AAS shows negligible effect of temperature on absorption performance. To improve the stripping performance, enhanced CO2 desorption (based on pH-shift) was studied by using asymmetric solutions of AAS. Higher molar ratios of amino acid shows better stripping and reduced absorption performance because lower pH shifts the CO2 reaction equilibrium towards the release of CO2. Also it has been observed AAS solutions have lower potential of membrane wetting due to its high surface tension. Further it has been proved AAS solutions have good recyclability.

Selective absorption of H2S from a gas mixture with CO2 in a microporous tube-in-tube microchannel reactor

In industrial gas processing, there is an increasing interest in gas absorption processes for the selective removal of H2S from gas streams with a high CO2/H2S ratio. In this work, the selective absorption of H2S from a gas mixture with CO2 into N-methyldiethanolamine (MDEA) in a microporous tube-in-tube microchannel reactor (MTMCR) was studied. A high H2S removal efficiency of 99.85% could be achieved. The effects of various parameters such as MDEA concentration, liquid and gas flow rates, gas–liquid ratio, absorbent temperature, mean micropore size and annular channel width of MTMCR on H2S removal efficiency and selectivity were explored. The results indicated that MDEA concentration, liquid and gas flow rates had significant influence on H2S removal efficiency and selectivity. With the increase of MDEA concentration and liquid flow rate, H2S removal efficiency increased while selectivity decreased. Increasing gas flow rate resulted in H2S removal efficiency decrease and the selectivity increase. The smaller micropore size and annular channel width led to higher H2S removal efficiency and lower selectivity. Furthermore, the micropore size had a bigger effect on H2S selective removal process than the annular channel width. The results obtained imply a great potential for MTMCR applied to the selective absorption of H2S.

A study visualizing the collapse of vapor bubbles in a subcooled pool

The condensation processes of vapor bubbles in a subcooled pool were recorded and analyzed, which could help to illustrate the mechanism of collapse of vapor bubbles and emission of microbubbles during Microbubble Emission Boiling (MEB). Vapor bubbles were injected into the subcooled pool through an orifice with the inner diameter of 4mm at different vapor volumetric flow rates. Visualized results showed that the bubble surface became rougher and more unstable with the increase in liquid subcooling and volumetric flow rate, during which four condensation features were confirmed and defined as smooth bubble regime, shape oscillation regime, transition regime and capillary wave regime, respectively. Fine surface wave formed after a while of condensation would enlarge the effective area of condensation, resulting in the acceleration of bubble condensation. Furthermore, the fine surface wave which might also lead to bubble collapse only appeared on bubble surface at liquid subcooling over 25K and vapor volumetric flow rate higher than 0.74m3/h, which corresponded to the occurrence conditions of MEB. After the sudden collapse of the vapor bubble with capillary wave, a great many microbubbles formed, with a greater velocity and much smaller radius with subcooling and vapor injection rate increasing. In the region of MEB, a strong surface wave usually appeared on vapor film before the film collapse and the emission of microbubbles. Nevertheless, the film surface formed in film boiling was relatively smooth compared with that formed in MEB. All of the experiments results and analysis illustrated that the strong surface wave introduced by condensation may be one of the reasons resulting in the formation of MEB.

Mass Transfer Performance of CO2 Absorption from Natural Gas using Monoethanolamine (MEA) in High Pressure Operations

Most carbon dioxide (CO2) absorption studies that use amine based solvents for flue gas treatments were conducted at atmospheric pressure. This study reports the absorption performance of monoethanolamine (MEA) for the removal of CO2 from natural gas (NG) at high pressure conditions. The absorption experiments were conducted in an absorption column packed with Sulzer metal gauze packing at 5.0 MPa operating pressure. The effects of gas flow rate (18.89–35.08 kmol/m2·h), liquid flow rate (1.81–4.51 m3/m2·h), MEA concentration (1.0–4.0 kmol/m3), and liquid temperature (27–45 °C) on the mass transfer performance were evaluated in terms of CO2 removal (%) and overall volumetric mass transfer coefficient (KGav). From this study, the KGav was found to increase with increasing liquid flow rate and MEA concentration. However, the mass transfer performance was not affected by the total gas flow rate. The optimum condition for liquid temperature was found to be at 40 °C.

Evaluation of hydraulic characteristics of a pilot-scale air-lift internal-loop bioreactor

Using sodium fluoride as tracer, residence time distribution technique was employed to evaluate the hydraulic characteristics of a pilot-scale Internal-Loop Airlift Bio-particle (ILAB) bioreactor that was a novel system for ammonia removal from wastewater. The results showed that the flow pattern of ILAB reactor was close to completely mixed reactor under all the tested air flow rates and liquid flow rates (with average N of 1.88). The total dead zone (TDZ) was 32.43% with biological dead zone (BDZ) of 20.66% and hydraulic dead zone (HDZ) of 8.95%. At higher air flow rates, the flow pattern of reactor approached that of completely mixed reactor (N from 2.72 to 1.54), and the increase of air flow rate gave rise to the decrease of TDZ in the reactor (from 36.24% to 23.00%). Whereas at higher liquid flow rates, the flow pattern of ILAB reactor got away from that of completely mixed reactor (N from 1.51 to 1.72), and the increase of liquid flow rate yielded a rise of TDZ in the reactor (from 28.48% to 36.84%). The study highlighted that the effect of air flow rate on flow pattern and TDZ of the reactor was greater than that of liquid flow rate.

Experimental study on vapour splitter in packed divided wall column

AbstractBACKGROUNDAdjustment of the vapour split in a divided wall column (DWC) is a great challenge. In order to resolve this problem, a vapour splitter was proposed and the properties and performance of the vapour splitter were examined in a number of experiments.RESULTSGas flow rates and vapour split changed significantly with blade angle in the range 50–10°. When the liquid flow rates on both sides were the same, the vapour split reduced with increasing liquid flow rate. The gas flow rate decreased with increase of liquid flow rate in the same side. The vapour split increased when the gas velocity decreased. When the V‐type cap angle was 50° the gas nonuniformity was minimum. The gas nonuniformity also varied with blade angle, but fortunately remained at a low level.CONCLUSIONThe device can adjust the vapour split regardless of operating conditions. The gas is distributed uniformly before entering the packed bed. There are some limitations to this device, but the results indicate that the prospects of our vapour splitter are promising. © 2014 Society of Chemical Industry

Flat sheet membrane contactor (FSMC) for CO2 separation using aqueous amine solutions

A new multi-flat-sheet membrane contactor (FSMC) was developed and used to investigate CO2 removal from CO2/N2 gas mixture using aqueous 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) solution in the presence and the absence of piperazine (Pz) as activator. The FSMC was operated under various experimental conditions in order to study the effect of liquid flow rate, gas phase composition, CO2 liquid loading and contactor configuration (number of membranes, type of membrane (PTFE, PP and laminated PTFE/PP) and fluid flow orientation (co- and counter-current)). For comparison purpose, MEA aqueous solution (the benchmark amine used in the CO2 capture process) was also tested under the same experimental conditions. The absorption rates through the membranes were found to increase with the increase of liquid flow rate and CO2 concentration in the gas phase and decrease with the raise of CO2 loading. Pz activated AHPD solution showed better performance than single AHPD solution, and similar absorption fluxes were obtained for AHPD+Pz and MEA solutions. As a proportional increase of the absorption rate with the number of membranes was observed, when required, more membranes can be easily added to a contactor module to increase the absorption performance. A two-scale model accounting for CO2 diffusion in the gas-filled membrane pores, CO2 and amines diffusion/reaction in the liquid-filled membrane pores and CO2 and amines diffusion/reaction in the liquid boundary layer was developed to describe the comportment of the multi-flat-sheet membrane contactor.

Model of bubble velocity vector measurement in upward and downward bubbly two-phase flows using a four-sensor optical probe

The knowledge of bubble behaviors is of considerable significance for a proper understanding and modeling of two-phase flows. To obtain the information on the bubble motion, a novel model was developed, by which the bubble velocity vector can be directly calculated from six time intervals measured with a four-sensor probe. The measurements of local bubble velocity vector and void fraction were performed in both upward and downward bubbly flows by using a four-sensor optical probe. The area-averaged void fraction and bubble velocity obtained from the probe agree well with those measured by other cross-calibration methods, and the measurement errors are within 15% under various flow conditions. Experimental results of the bubble velocity vector reveal that the bubble lateral migration may be suppressed in upward flows, but be strengthened in downward flows as the liquid flow rate increases. Also, with an increase in gas flow rate, the bubble velocity distribution varies into the power–law profile in upward flows, but into an off-center peak profile in downward flows. In addition, the void fraction shows a core peak distribution at low void fraction for downward flows, but a wall peak distribution for upward flows. However, when the void fraction is relatively high, it displays an off-center peak distribution for downward flows but a core peak distribution for upward flows.

Investigation on heat transfer characteristics of R134a spray cooling

Due to its high local heat transfer coefficients, spray cooling is a vital technique for thermal management of high heat flux electronic devices. In this study, an experimental system using R134a as the working fluid was designed and built to study the heat transfer characteristic of spray cooling. The influences of the liquid flow rate, the vapor phase mass fraction and the liquid subcooling of the two phase R134a spray cooling on the heat transfer performances were discussed. The experimental results show that the heat transfer coefficient increased with the increasing liquid flow rate when the liquid fluid rate was less than 1.6L/min. However, the enhancement on heat transfer coefficient owing to the increase of liquid flow rate was insignificant while the flow rate was higher than 1.6L/min. A maximum surface heat flux of 325.99W/cm2 was achieved using R134a spray cooling while the temperature of the test surface was about 42.4°C at the flow rate of 2.15L/min.

Effect of working parameters and nozzle wear rate onto the spray quality in use of different fan flat nozzle

The subject of the analysis was the influence of working parameters (working pressure and working speed) on +drop tracks size and changes in flow rate level from flat fan nozzle. New nozzles and nozzles after laboratory wear were tested. The influence of nozzles wear on +drop tracks size was examined. It was found that increase in liquid flow rate results in higher values of mean diameter of +drop track. Increase in working pressure or working speed cause decrease in +drop tracks size and reduce merging of drops on spray surface. Increase in wear degree was followed by increased coverage rate. This phenomenon is especially dangerous when using nozzles with considerable wear degree for agricultural spray since this poses ecological threat to environment.

Liquid Film Falling on Horizontal Plain Cylinders: Numerical Study of Heat Transfer in Unsaturated Porous Media

In this article, numerical investigation of liquid film falling over three horizontal plain cylinders is presented. The flow Reynolds number of 50 to 3000 and cylinder diameters of 0.022 m, 0.123 m, and 0.1 m are employed. Numerical predictions are obtained using FLUENT, a proprietary computational fluid dynamics (CFD) code for 2D configurations of the three cylinders. The mathematical approach is based on the volume of fluid (VOF) method to account for two fluid phases, namely air and water. The research reported in this paper is motivated by the possibility of using detailed numerical simulations of the phenomena that occur in beds of irrigated porous media to cool horticultural produce. The effect of liquid flow rate (Reynolds number) and the cylinder diameter on heat transfer coefficient have been studied. It is found that increasing liquid flow rate or Reynolds number results in an increase in the heat transfer coefficients, and decreasing the cylinder diameter results in an increase in the heat transfer coefficient. The numerical results provide an insight into the cooling mechanisms within beds of unsaturated porous media. This research is part of an overall study of horizontal cylinders falling film flow and heat transfer.

Wpływ parametrów pracy i zużycia rozpylaczy na jakość oprysku z wykorzystaniem różnych rozpylaczy płaskostrumieniowych

The subject of the analysis was the influence of working parameters (working pressure and working speed) on +drop tracks size and changes in flow rate level from flat fan nozzle. New nozzles and nozzles after laboratory wear were tested. The influence of nozzles wear on +drop tracks size was examined. It was found that increase in liquid flow rate results in higher values of mean diameter of +drop track. Increase in working pressure or working speed cause decrease in +drop tracks size and reduce merging of drops on spray surface. Increase in wear degree was followed by increased coverage rate. This phenomenon is especially dangerous when using nozzles with considerable wear degree for agricultural spray since this poses ecological threat to environment.

The influence of flow rate on inter-nucleation site heat transport

The main topic of this paper is the influence of vertically aligned nucleation sites on each other in upward flow boiling. A setup was constructed to facilitate vertical up-flow of deminiralized water under saturation conditions. The main test section is a glass channel with a set of vertically aligned bubble generators. Each bubble generator is operated independently, where power and wall temperature are registered and the vapour bubbles are visualized by a high-speed camera. During the experiments, the downstream bubble generator (BG1) power is kept constant, while the power fed to the upstream bubble generator (BG2) is incrementally increased. Two main trends have been identified. The first trend is dominated by added convection from one site to the other. Both bubble frequency and detachment diameter on BG1 increase with increased power fed to upstream BG2. This effect decreases with increasing inter-site distance and becomes more significant with increasing liquid flow rate. When vapor bubbles start nucleating from BG2, these vapor bubbles inhibit bubble nucleation BG1 and can even lead to deactivation of this nucleation site. This second trend is only weakly dependent on inter-site distance, since the inhibition originates from bubbles flowing past BG1 in close proximity.

Effect of transesterification of vegetable oil on liquid flow number and spray cone angle for pressure and twin fluid atomizers

Vegetable oils as energy source can either be used in their pure form or as bio-diesels after transesterification. In the present study, performance of a hollow cone pressure atomizer and a twin fluid atomizer with sunflower straight vegetable oil and its ester (bio-diesel) has been compared. The pressure drop (ΔP) of liquid across the atomizer and the liquid flow rate (Q) have been measured for different liquid temperatures and atomizer liquid flow number (FN) and coefficient of discharge (Cd) are calculated. The spray cone angles have been evaluated from optical images of the sprays at different conditions. Though, the flow number is found to increase upon transesterification in case of the twin fluid atomizer, an opposite trend is observed for the hollow cone pressure atomizer. It shows that less pumping power is required for the atomization of sunflower oil compared to that of its ester in case of hollow cone atomizer. This is attributed to the smaller size of the air core formed due to higher viscosity of pure sunflower oil. The lower viscosity of bio-diesel causes a higher spray cone angle compared to that with pure vegetable oil for both the atomizers. In case of hollow cone pressure atomizer, the spray cone angle increases with the increase in liquid flow rate, while in the twin fluid atomizer an increase in air pressure increases the cone angle.