Liquid Entrainment Research Articles

Processing of Zn-Substituted calcium silicate layers on Y-Tzp bioceramics by dip coating

Ceramic layers based on calcium silicate non-substituted and substituted by Zn with different thickness, were developed by immersing porous Y-TZP disks into SiO2–CaO–ZnO–P2O5 glass suspensions with ZnO contents in the range of 0–20 mol%. The effect of the disk surface porosity and the slip solid loading on the formation of the dip coated layer was investigated. Special emphasis was given to the ZnO content of the dip coating slurries and its influence on the thickness and composition of the sintered layer. The greater chemical stability of the 20 mol% ZnO-substituted glass powder during aqueous colloidal processing resulted in slips with low viscosity values; whereas the high dissolution rate of the glass having 10 mol% ZnO significantly increased the slip viscosity. The liquid entrainment mechanism at the initial stage was accelerated either by using 10 mol% ZnO-substituted glass slips or by increasing the slip solid loading. The casting rate for longer immersion times markedly increased by increasing the surface porosity of Y-TZP disks. Sintered layers with thickness ~30–70% lower were produced using the glass dip coating slip with 20 mol% ZnO in comparison to 10 mol% ZnO. The main crystalline phase of the coated sintered layers was Ca3Si3O9, Ca2ZnSi2O7 and ZnSiO4 for the glasses with 0, 10 and 20 mol% ZnO, respectively.

Extraction of nobiletin and tangeretin with antioxidant activity from peels of Citrus poonensis using liquid carbon dioxide and ethanol entrainer

ABSTRACT Extraction of nobiletin and tangeretin from peels of Citrus poonensis was conducted with liquid CO2 and ethanol entrainer. Yields of nobiletin (6.7 mg/g-dry peel) and tangeretin (4.4 mg/g-dry peel) for liquid CO2 with ethanol entrainer extractions (25ºC, 10 MPa, 60 min with CO2-ethanol mole fraction of 0.13) gave 24% and 19% higher yields compared to conventional ethanol extraction. The DPPH radical scavenging activity of the extracts obtained from liquid CO2 with ethanol entrainer showed to be similar to ascorbic acid and α-tocopherol.

Identification of gas-liquid two-phase flow patterns in dust scrubber based on wavelet energy entropy and recurrence analysis characteristics

For a wet dust scrubber, dust collection efficiency is tightly connected with the gas-liquid two-phase flow pattern. Using the characteristic parameters selected by current flow pattern identification methods, regions of significant coincidence exist among different patterns, thereby leading to a decline in the identification efficiency. In this study, a new method for processing the wavelet decomposition signal of the dust collector pressure was proposed to obtain the characteristic parameters that distinguish the flow pattern. Firstly, detailed information regarding the different frequency bands of the pressure signal was extracted via wavelet analysis. Then, in combination with the information entropy theory, wavelet energy entropy (WEE) was proposed to evaluate the uniformity of energy distribution in different frequency bands. The results show that WEE is sensitive to the change in gas-liquid two-phase flow patterns, and the corresponding distinguishing efficiency of flow patterns is 92.5%. There was only a small amount of crossover between the shear liquid curtain and entrainment air bubble pattern. For this, using the recursive analysis method (RAM), the characteristic recurrence plots (RP) and recurrence quantification analysis (RQA) of the original pressure signals and the wavelet decomposition signal with different frequency bands were obtained. Results show that the RP characteristics can intuitively reflect the gas-liquid flow state of different flow patterns. Although RQA characteristics are not sensitive to the change in low-level gas/liquid resonance flow pattern in the dust scrubber, it exhibits strong distinction to the evolution of other flow patterns. It effectively compensates for the crossover at the flow pattern distinguish between the shear liquid curtain and entrainment of air bubble using the parameters of the wavelet energy entropy. It is the highlight of this article that the combination of WEE and recurrence characteristics can effectively address the problems of high coincidence of flow pattern features in the dust scrubber.

A pressure drop model for the annular-mist flow in vertical Venturi

Venturi is one of the most commonly used flowmeters for measuring gas-liquid flow at the natural gas wellhead. A better understanding of the flow mechanism and the causes for pressure drop is necessary for the establishment of the measurement model. In this study, a one-dimensional pressure drop model between the two pressure taps of Venturi has been proposed for vertical annular-mist flow. The relations between the liquid film, entrainment rate, void fraction, and velocity slip have been revealed when the annular flow went through Venturi. We consider the gas acceleration in the throat of Venturi. The proportions of various pressure drops are given. The experimental results show that the relative errors of the pressure drop have a confidence probability of 98.5% within 10%. The predicted results are also in good agreement with the on-site data. It proves that the new pressure drop model has good performance.

An experimental analysis over phase separators applied to household refrigerators

The objective of this study was to experimentally evaluate the influence of liquid-vapor separators in the performance of a novel dual-evaporator cycle architecture for household refrigerators. A refrigerator prototype was designed and constructed and two T-separators with vapor branches of 10 mm and 28 mm in diameter were tested with compressor speeds from 2000 to 3500 rpm and duty cycle from 10% to 45%. A visualization section was installed to capture the refrigerant flow through the acrylic T-separators. Cooling capacity and coefficient of performance were measured and photographs of the refrigerant flow in the separators were used to gain a better understanding of the results. The study concluded that the liquid entrainment in the separator of 10 mm increased the freezer coefficient of performance up to 55% and the system performance for the same duty cycle in 11%, in average, when comparing to the system with 28 mm separator with no liquid drag. The liquid entrainment also compromised the compressor reliability and decreased the fresh food COP up to 29%. The separator of 28 mm increased the fresh food performance and provided a reliable system during the entire tested range. Also, with the use of this separator, liquid was able to accumulate at duty cycles of 40% and 45% and, at 45%, the system reached its maximum cooling capacity and COP at 16 °C and 3500 rpm, around 6% higher than the average global COP of the reduced diameter separator. Finally, pull down tests were performed to verify the systems performance during transient conditions. It was shown that the liquid entrainment tended to increase the pull down time.

Physical and numerical modeling of liquid slag entrainment in mould during slabs casting

The paper presents results of physical and numerical modeling of liquid slag entrainment during continuous casting of steel slabs process. The main aim of this work was to determine the critical casting speed and also to specify, which entrainment mechanism is most responsible for transport of slag droplets into steel volume. Physical modeling was based on water-oil model of mould, made on reduced linear scale of Sl = 0.4. In mathematical modeling, Realizable k-ε and LES WALE models were used to describe turbulent motion of water and oil, whereas Volume of Fluid model was used to take into account interactions between phases. It was found, that the main cause of slag entrainment is the formation of von Karman vortex in the vicinity of submerged entry nozzle. The results of laboratory experiments and numerical simulations were compared each other. Both method are a useful tools for modeling of slag entrainment. Great agreement was found between laboratory experiments and numerical simulation carried out using LES WALE model, regarding the shape of the oil and oil entrainment as a result of vortex structures formation. However, in the simulation case using Realizable k-ε model, the oil entrainment hasn’t been modeled for the conditions under consideration.

Evaluation of Wave Characteristics in Annular Flow in Horizontal Pipes

Annular flow experiments in horizontal flow in pipes were conducted with emphasis on wave characteristics (wave velocity, wave frequency) and liquid film thickness. The experiments were conducted using water/air in a 0.0504m pipe diameter with a total flow loop length of 28.68m. Liquid film thickness in all the flow matrix in this study, were observed to be decreasing with increase in gas velocity while increasing with increase in liquid velocity. The decreasing tendency with superficial gas velocity was because of liquid entrainments which were accounted. Pan and Hanratty correlation for liquid entrainment was chosen because it gave the most realistic results among other correlations from the experimental data. Wave velocity and wave frequency were presented to be increasing with increase in superficial gas velocity in annular flow. For wave frequency, it was observed that both superficial liquid and gas velocities have great impact on it. In annular flow in horizontal pipe, it was also observed that the lower the superficial liquid velocity, the lower the amplitude and the higher the wave frequency. This indicates that at low liquid velocity, more ripple waves occurred and at this time more energy were dissipated which resulted to the high frequency observed in this study. However, several correlations where compared with the obtained wave frequency in this study, but [2] preferably matched better as the superficial liquid velocity increases from 0.0903m/s to 0.1851m/s.

Development and performance study of a natural silk fiber facial mask paper

Facial masks are beauty products which composed of a facial mask paper and beauty solution. Silk contains the amino acid structure closest to the human skin, and has the skin-friendly, cosmetic and antibacterial functions, but the common method for making nonwoven facial mask paper is not suitable for silk. In this paper, the silkworm’s spinning path is intervened manually to obtain a smart silk facial mask paper (SMC) of controllable thickness, so that the sericin on the silk fiber is well preserved. In the experiment where the SMC is compared with the nonwoven 384-cuprammonium rayon facial mask paper (CRMC) which is the most widely used in the market, it is found that the ways of forming the two facial mask paper are completely different, and therefore the morphologies under SEM are obviously different. The thickness of the SMC is 0.183 mm and the areal weight of it is 38.0 g/m2. It is very close to the CRMC (0.187 mm, 38.4 g/m2). The porosity of the SMC is 84.0%, which is slightly lower than that of the CRMC (86.3%), but its pores are well distributed. Compared with the CRMC, the smart SMC has higher dry and wet strength, lower elongation, slightly lower air permeability and liquid entrainment rate, and better antibacterial performance.

Evaluation of ionic liquid separation ability for the benzene–methanol mixture by extractive distillation

AbstractBACKGROUNDBenzene–methanol azeotrope can be formed at atmospheric pressure. Extractive distillation is widely used in the separation of azeotrope. The key factor for extractive distillation is the selection of entrainer. The minimal total annual cost of extractive distillation process can be used as objective function to evaluate the separation performance of ionic liquid entrainer. Intermolecular interaction energy can be used to analyze separation mechanisms.RESULTAn Aspen Plus software database belonging to the three ionic liquids 1‐hexyl‐3‐methylimidazolium acetate, 1‐octyl‐3‐methylimidazolium acetate and 1‐decyl‐3‐methylimidazolium acetate was established. The minimal total annual costs of three extractive distillation processes for the separation of benzene–methanol mixture with different ionic liquids were obtained by sequential iterative method. The feed rate of entrainer was also obtained under the optimized conditions. Among the three extractive distillation processes with different ionic liquid, the total annual cost and the entrainer feed rate of the extractive distillation process with 1‐hexyl‐3‐methylimidazolium acetate as entrainer are the smallest. The intermolecular interaction energies in the ternary system of benzene–methanol–ionic liquid were obtained using the Gaussian 09 software package based on the density functional theory. The separation mechanisms and the extractive distillation process of benzene–methanol azeotrope with ionic liquid as entrainer was interpreted by the intermolecular interaction energy.CONCLUSIONThe results show that the separation ability of 1‐hexyl‐3‐methylimidazolium acetate is higher than that of 1‐octyl‐3‐methylimidazolium acetate or 1‐decyl‐3‐methylimidazolium acetate. Intermolecular interaction energy analysis can be used in the screening and design of ionic liquid entrainer. © 2019 Society of Chemical Industry

Impact of wildfire on 137Cs and 90Sr wash-off in heavily contaminated forests in the Chernobyl exclusion zone

Wildfires may play a role in redistributing radionuclides in the environment in combination with hydrological processes such as surface runoff and soil erosion. We investigated plot-scale radionuclide wash-off at forest sites affected by wildfires in the Chernobyl Exclusion Zone (CEZ). We also compared speciation of the washed-off radionuclides with those in previous studies conducted just after the accident in 1986. We observed the surface runoff and the radionuclide wash-off with a soil erosion plot at forest and post-fire sites during May–September 2018. In the post-fire site, 2.81 mm of surface runoff was observed in at least three flow events resulting from 285.8 mm total rainfall. The fluxes of dissolved and particulate 137Cs were estimated as 4.9 and 161 Bq m−2, respectively. The dissolved phase 90Sr flux was estimated as 214 Bq m−2. At the forest site, a single surface runoff (0.67 mm) event was generated by rainfall of 182.2 mm. The fluxes of dissolved and particulate 137Cs wash-off values were 6.2 and 8.6 Bq m−2, respectively. The flux of dissolved 90Sr wash-off from the forest was estimated as 45.1 Bq m−2. The distribution coefficient, which indicates the dissolved-particulate form of radionuclides, in the post-fire site was 30 times higher than that in the forest site, indicating the importance of particulate 137Cs wash-off after fire in the CEZ. The entrainment coefficients for dissolved and particulate 137Cs concentrations were around 50 times lower than those obtained in the corresponding position within the CEZ immediately after the accident in 1987. The effect of downward migration of 137Cs over 30 years led to decreased entrainment coefficients for dissolved and particulate 137Cs. The effect of downward migration of radionuclides was considered sufficient to indicate changes in normalized liquid and solid radionuclides wash-off entrainment coefficient and the distribution coefficient in this study.

Liquid entrainment through a large-scale inclined branch pipe on a horizontal main pipe

T-junction structures play an important role in nuclear power plant systems. Research on liquid entrainment is mostly based on small-scale branch pipes (d/D ≤ 0.2) and attention paid to large-scale branch pipes (0.33 < d/D < 1) is insufficient. Accordingly, this study implements a series of experiments on the liquid entrainment of T-junction with different angles (32.2°,47.9°,62.3°,90°) through a large-scale branch (d/D = 0.675).The onset liquid entrainment is related to the gas phase Froude number Frg, the dimensionless gas chamber height hb/d and the branch pipe angle θ. As Frg increases, hb/d also rises. With a constant hb/d, the onset liquid entrainment changes from droplets entrainment by the gas phase to that by the rising liquid film. The steady-state liquid entrainment is related to w3g, h/d and θ. With constant w3g and h/d, the branch quality grows as the branch angle increases. With a certain h/d, the branch quality increases, as the w3g number increases.

Mass-Transfer Characteristics and Optimization of a Hydrophilic Ceramic Membrane Contactor for SO2 Absorption

Postcombustion SO2 capture—from a high-volume flue gas—calls for a separator which should possess a high gas/liquid ratio concurrently without causing liquid flooding and entrainment. This study ai...

Effect of bubble plume on liquid phase flow structures using PIV

In this study, particle image velocimetry (PIV) technique was used for the quantitative visualization and analysis of the liquid phase flow structure driven by a chain of air bubbles in a rectangular bubble column. So, we aimed to provide the recirculation flow pattern and turbulence characteristics in the vicinity of rising bubbles. To this aim, a simple experimental set-up was built, the liquid phase was seeded with 10 µm hallow glass particles. The illumination system consists of a 5 W argon laser source. Images were taken with a high-speed camera (Teledyne Dalsa, Falcon 1.4M100 HG CMOS). The sequence of different bubbles trajectories in water and glycerin solution of high viscosity was studied in order to understand the induced liquid phase flow structure. When the liquid viscosity increases, the instabilities of the liquid velocity field disappears showing the liquid entrainment in the bubbles wake which tends to rise in vertical alignment around the central axis of the column. Furthermore, the viscous force reduces the pseudo-turbulence induced by the rising bubbles, which increases the vertical liquid velocity.

A Study on Onset of Liquid Entrainment in Low Pressure Depressurization System of Advanced Passive Pressurized Water Reactors

The low-pressure depressurization system (LPDS) of advanced passive pressurized water reactors (PWRs) is designed to provide depressurization of the reactor coolant system during a small break loss-of-coolant accident (LOCA). The liquid entrainment to the LPDS is important for the safety case of the advanced passive PWRs due to the significant increase of the pressure loss and the depressurization rate versus mass loss characteristics. The existing experimental researches on the liquid entrainment at LPDS have been reviewed, and the intermittent entrainment mechanism and the continuous entrainment mechanism are identified. The intermittent entrainment is closely related to the flow regime transition from the horizontal stratified flow to the intermittent flow in the hot leg where the LPDS port is located. The horizontal stratification model previously developed for the FULL SPECTRUM LOCA evaluation model has been assessed against the entrainment onset data in the available LPDS entrainment experiments, i.e., the ATLATS air–water experiment, the ADETEL air–water and steam–water experiments, and the full-scale FATE air–water experiment. The prediction matches the measure data well especially in the full-scale FATE experiments. The comparison results also confirmed the scalability of the horizontal stratification model with the applicability of the horizontal stratification criterion to the full-scale PWR condition. The uncertainty factors that impact the depressurization system entrainment onset are discussed for the future improvements. This work provides the direction to accurately model the entrainment onset for LPDS and improve the simulation of LOCA in advanced passive PWRs.

Jet-film contact devices for heat and mass transfer processes in heat power engineering

One of the main production processes for many branches of industry is cooling of recycled\\circulating water, which takes place in the cooling towers. The most important parameter to determine the cooling efficiency of water in the cooling tower is the contact surface of air and water. The existing designs of contact devices are highly effective in cooling the liquid, but they are complex to manufacture and expensive. In this regard, a new design of the jet-film contact device was developed, which allows creating a highly developed contact surface of liquid and gas phases. Mathematical model of the element of jet-film contact device was built by means of specialized software package and numerical calculations were carried out. Paper includes the study of behaviour of liquid and gas phases in the device element, and the mathematical dependences were obtained. Dependency of the liquid entrainment from device when changing the water flow rate was studied. Also, the comparison of designs with different location of holes within the wall elements was also carried out. Modernization of the studied jetfilm contact device was carried out in order to identify the direction which to follow for improvement of design properties. This paper proposes an engineering method for calculating the jet-film contact device.

The Application of Computational Thermo-Fluid-Dynamics to the Simulation of Hybrid Rocket Internal Ballistics with Classical or Liquefying Fuels: A Review

The computational fluid dynamics of hybrid rocket internal ballistics is becoming a key tool for reducing the engine operation uncertainties and development cost as well as for improving experimental data analysis. Nevertheless, its application still presents numerous challenges for the complexity of modeling the phenomena involved in the fuel consumption mechanism and its coupling with the chemically reacting flowfield. This paper presents a review of the computational thermo-fluid-dynamic models developed for the internal ballistics of hybrid rockets burning gaseous oxygen with classical polymeric or paraffin-based fuels, with a special focus on the interaction between the fluid and the solid fuel surface. With the purpose of predicting the local fuel regression rate, which is the main parameter needed for the hybrid rocket design, the model is coupled with an improved gas/surface interface treatment based on local mass, energy and mean mixture-fraction balances, combined to either a pyrolysis-rate equation in the case of classical polymers, or to an additional equation for the liquid paraffin entrainment fraction of the total fuel consumption rate. A number of experimental test cases obtained from the static firing of two different laboratory-scale rockets are simulated to determine the models’ capabilities, showing very good agreement between the calculated and measured fuel regression rates with both standard pyrolyzing and liquefying fuels. The prediction of the chamber pressure measured with paraffin fuel resulted in it being more cumbersome for the single-phase flow assumption. The advantages and limitations of the models are discussed.

Saturated pool boiling heat transfer of acetone and HFE-7200 on modified surfaces by electrophoretic and electrochemical deposition

Boiling heat transfer intensification is of big relevance to energy conversion and conservation, materials and resources saving, and electronics cooling. This work aims to enhance saturated pool boiling of well-wetting liquids, i.e., acetone and HFE-7200 on nanoparticles-deposited surfaces by electrophoretic deposition and on microporous foam surfaces by electrochemical deposition. The electrophoretic-deposited surfaces enhance the heat transfer coefficient of acetone and HFE-7200 by up to 70% and 190%, respectively. However, the critical heat flux is not improved on electrophoretic-deposited surfaces. The electrochemical-deposited surfaces increase the boiling heat transfer coefficient by up to 370% and the critical heat flux by more than 30%. Bubble dynamics were visualized simultaneously. The bubble departure diameter from experiments can be predicted by a dynamic force balance model within a ±20% error band. A mechanistic heat transfer model was proposed for modified porous surfaces, including not only the heat fluxes from microlayer evaporation and transient conduction but also the heat flux from micro-convection due to liquid agitation and entrainment by growing and departing bubbles. The mechanistic heat transfer model can predict experimental pool boiling curves of acetone and HFE-7200 on electrophoretic-deposited and electrochemical-deposited surfaces relatively well, especially for the isolated bubble regime where most bubbles are isolated and bubble coalescence is not intensive. Besides, the critical heat flux of a modified surface can be estimated if the initial (maximum) wicked volume flux on the structured surface relative to the smooth surface is considered.

Pilot application of a novel Gas–Liquid separator on offshore platforms

Existing devices available on offshore gas/oil platforms are incapable of realizing complete separation of the liquid phase from wet natural gas. This results in eccentric motion of rotors and eventually causes trouble halting of natural-gas compressors. To tackle this problem, use of a novel gas-liquid separator has been reported for offshore oil platform applications. A pilot scale test was performed using the proposed equipment. Results of the test demonstrate that the optimum operating point of the pilot plant corresponds to a flow rate of 90 m3/h (30 °C, 5.0 MPa), and this could be used as a reference for subsequent industrial scale-ups. The results of the pilot test lead to the conclusion that the said novel separator has higher separation efficiency when compared against conventional industrial devices used on oil platforms. Using of the proposed equipment is aimed at alleviating the problem of liquid entrainment of natural gas entering the compressor, increasing compressor service life, and reducing operational and maintenance costs. The proposed study provides a new outlook towards engineering design of offshore-oil-platform equipment of theoretical as well as practical value.

Experimental and theoretical investigation on pool entrainment under small air flow rate

The liquid entrainment is a ubiquitous phenomenon in nuclear engineering. In the scenario of SBLOCA, liquid entrainment plays an important role threatening the core safety. Numerous research has been conducted on the mechanism of pool entrainment. Part of experiment data could be predicted well by Kataoka-Ishii entrainment correlation which has been widely used. However, most research focused on the pool entrainment is conducted under intermediate or high gas flow rate. The Kataoka-Ishii correlation is also less accurate when air flow rate is small. Therefore, an experimental investigation under small air flow rate is important to conduct. This paper demonstrates experiment apparatus, instrumentation, experiment phenomenon as well as relevant analysis. An entrainment correlation is proposed based on the experiment data. The relative uncertainty of fitting entrainment correlation based on the experiment data is within ±30%. Entrainment factor influenced by exit effect of different location is specifically deducted. The transition region of pool entrainment is analyzed and can be estimated by flow pattern map. Some typical entrainment patterns under different air flow rate are also illustrated and described.

Experimental research on bubble size distribution and vapor quality at the outlet of vertical narrow channel

The presence of bubbles exerts a strong influence on pressure drop, heat transfer, flow pattern, and many other flow characteristics. Due to the complexity of two-phase flow boiling, it is not easy to carry out experimental research. An experimental setup based on ultrasonic detection method is built up in this paper. The present study investigates bubble size distribution and vapor quality in liquid-gas two-phase flow in a vertical narrow channel with the cross section of 3×20 mm. Bubble size distribution is heavily affected by the heat power and mass flux, which means that different flow patterns show different bubble size distributions. Vapor quality is also obtained by the ultrasonic attenuation method, which is compared to the theoretical calculation. The ultrasonic detection model is mainly applied in the bubble-coalesced flow. As the vapor quality is small, the detection value is close to the theoretical value, and this detection model is suitable for nucleate boiling. As the vapor quality is increased, the deviation is larger. By comparison with the theoretical calculations, it is necessary to modify the ultrasonic detection model to fit different flow patterns, which is helpful to study the liquid entrainment mechanism in the micro-channel (especially when the inner diameter is less than 5 mm) in the future.