scholarly journals Facile fabrication and characterization on alginate microfibres with grooved structure via microfluidic spinning

2019 ◽  
Vol 6 (5) ◽  
pp. 181928 ◽  
Author(s):  
Xiaolin Zhang ◽  
Lin Weng ◽  
Qingsheng Liu ◽  
Dawei Li ◽  
Bingyao Deng
Keyword(s):  
Flow Rate ◽  
Loss Modulus ◽  
Fibre Diameter ◽  
Morphological Structure ◽  
Flow Rates ◽  
Alginate Solution ◽  
The Core ◽  
Facile Fabrication ◽  
Fabrication And Characterization ◽  
Alginate Fibres

Alginate microfibres were fabricated by a simple microfluidic spinning device consisting of a coaxial flow. The inner profile and spinnability of polymer were analysed by rheology study, including the analysis of viscosity, storage modulus and loss modulus. The effect of spinning parameters on the morphological structure of fibres was studied by SEM, while the crystal structure and chemical group were characterized by FTIR and XRD, respectively. Furthermore, the width and depth of grooves on the fibres was investigated by AFM image analysis and the formation mechanism of grooves was finally analysed. It was illustrated that the fibre diameter increased with an increase in the core flow rate, whereas on the contrary of sheath flow rate. Fibre diameter exhibited an increasing tendency as the concentration of alginate solution increased, and the minimum spinning concentration of alginate solution was 1% with the finest diameter being around 25 µm. Importantly, the grooved structure was obtained by adjusting the concentration of solutions and flow rates, the depth of groove increased from 278.37 ± 2.23 µm to 727.52 ± 3.52 µm as the concentration varied from 1 to 2%. Alginate fibres, with topological structure, are candidates for wound dressing or the engineering tissue scaffolds.

Microfluidic Fabrication of Helical Ca-Alginate Hydrogel Fibers

2021 ◽  
Vol 1035 ◽  
pp. 843-850
Author(s):  
Sha Chen ◽  
Jing Hua Gong ◽  
Jing Hong Ma
Keyword(s):  
Flow Rate ◽  
Helical Structure ◽  
Outer Flow ◽  
Flow Rates ◽  
Conductive Materials ◽  
Responsive Polymers ◽  
The Core ◽  
The Past ◽  
Sheath Fluid ◽  
Collection Tube

Helix is a sophisticated structure in nature and has many unique functions which makes it possible to store more information and energy, even receive more sensitive signals. Besides, as an effective method for preparing hydrogel fibers, microfluidic spinning has achieved unprecedented development in the past decade. However, hydrogel fiber with helical structure has began to be studied only in recent years. In this paper, the helical hydrogel fibers were prepared by the microfluidic spinning method. The microfluidic chip was assembled by PDMS connector, collection tube, inner and outer channels. Sodium alginate (SA) and calcium chloride were used as the core fluid and sheath fluid, respectively. By designing and adjusting the length of the chip, changing the concentration of SA and the ratio of two flow rates (inner flow rate/outer flow rate), a continuous and uniform helical hydrogel fiber was prepared. The relationships between the diameter of the fiber, the pitch of the helix and the concentration of SA, the ratio of two flow rates were discussed. The results showed that the diameter of the fiber was mainly affected by the core fluid. Within a certain range, as the concentration of SA increased, the diameter of the fiber increased. Besides, the pitch of the helix was greatly affected by the flow rate of sheath fluid. As the velocity of the sheath fluid increased, the pitch of the fiber increased. Such helical fiber could be used in micro sensors when added some conductive materials or crosslinked with some temperature responsive polymers such as N-isopropylacrylamide.

Adsorption/Retention of Petroleum Sulfonates in Berea Cores

1977 ◽  
Vol 17 (05) ◽  
pp. 353-357 ◽  
Author(s):  
J.H. Bae ◽  
C.B. Petrick
Keyword(s):  
Adsorption Isotherm ◽  
Aqueous Solutions ◽  
Flow Rate ◽  
Oil Recovery ◽  
Reservoir Rock ◽  
Equivalent Weight ◽  
Flow Rates ◽  
The Core ◽  
Petroleum Sulfonate ◽  
Pass Through

Abstract A series of petroleum sulfonate adsorption experiments was conducted in 2-in.-diameter, 2-ft-long Berea cores initially saturated with 1-percent NaCl brine. The sulfonates used had an average equivalent weight of 430 with a broad equivalent-weight distribution. The concentration ranged from 0.01 to 8 per cent. The flow rates investigated ranged from 2 to 36 ft/D. Adsorption was determined either from analysis of the effluent concentrations or by extraction of sulfonates from the core. The physical properties of the solutions were also measured. In several tests, Na2CO3 was used as a sacrificial chemical, either in a preflood or added to the sulfonate solution. It was found that at certain concentrations, apparent adsorption is dependent on the flow rate. The sulfonate adsorption isotherm was found to pass through a maximum. The value of the pass through a maximum. The value of the adsorption maximum and the concentration at which it occurs are also dependent on the flow rate. The time required for adsorption equilibrium was found to increase with increasing sulfonate concentration. A sacrificial chemical reduced the sulfonate adsorption. However, sulfonate adsorption increased gradually with time. Adsorption tests should be conducted at realistic flow rates. Introduction One of the major problems in surfactant flooding is the adsorption of surfactants on the reservoir rock. If adsorption is excessive, surfactants are depleted rapidly from the slug as it moves through the reservoir; consequently, it loses the ability to lower the oil-water interfacial tension. Thus, the magnitude of adsorption is an important technical as well as economic parameter. It has been reported that the adsorption of petroleum sulfonates is selective. The high-equivalent-weight sulfonates are adsorbed preferentially whole low-equivalent-weight preferentially whole low-equivalent-weight sulfonates show almost no adsorption. Most of the adsorbed sulfonates had an equivalent weight of 500 or more. This type of fractionation was considered to be the main cause for poor oil recovery in a field pilot test. The literature data on the adsorption of petroleum sulfonates from aqueous solutions indicate petroleum sulfonates from aqueous solutions indicate that there is a maximum in the adsorption isotherm. Furthermore, the adsorption of sulfonate is reduced significantly when sacrificial chemicals are used. The experimental methods used in these measurements differ from one another and, on occasion, the adsorbed sulfonates are defined to be the amount extracted by a solvent after a brine flush. The term "adsorption" is used here rather loosely. Some people prefer the term retention to adsorption since there may be physical retention in a core. The physical retention may or may not exist in a given experiment and detection of it may be very difficult. The objective of this work is to investigate the adsorption phenomenon in dynamic core tests. Several questions are examined: How is the adsorption isotherm related to the general properties of the solution? Do the dynamic test conditions affect the adsorption measurement? Are sacrificial chemicals useful in reducing sulfonate adsorption? EXPERIMENTAL PROCEDURES The petroleum sulfonate used was a blend of sulfonates, TRS 18 and TRS 40 obtained from Witco Chemical Co., and has an average equivalent weight of 430. The equivalent weight ranged from 250 to 650, with about 80 percent ranging from 350 to 550, almost evenly distributed. Isopropyl alcohol was used as a cosolvent at 1/10 of the sulfonate concentration. A 1-percent NaCl brine was used as the aqueous medium. Weight percentage is used throughout this paper. All adsorption tests were conducted at room temperature of 72 degrees F in 2-in.-diameter, 2-ft-long Berea cores saturated with brine. The permeability to brine in all tests was 450 + 25 md. The sulfonate solution was injected continuously into the cores using a positive-displacement pump. The produced fluids were collected in a fraction collector. In most cases, at the end of sulfonate injection, the sulfonate in the core was extracted immediately with a methanol-chloroform mixture. SPEJ P. 353

scholarly journals Cellular Nutrition in Complex Three-Dimensional Scaffolds: A Comparison between Experiments and Computer Simulations

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Claudia Bergemann ◽  
Patrick Elter ◽  
Regina Lange ◽  
Volker Weißmann ◽  
Harald Hansmann ◽  
...  
Keyword(s):  
Shear Stress ◽  
Cell Viability ◽  
Computer Simulations ◽  
Flow Rate ◽  
Oxygen Supply ◽  
Three Dimensional ◽  
Flow Rates ◽  
The Core ◽  
Local Oxygen

Studies on bone cell ingrowth into synthetic, porous three-dimensional (3D) implants showed difficulties arising from impaired cellular proliferation and differentiation in the core region of these scaffolds with increasing scaffold volumein vitro. Therefore, we developed anin vitroperfusion cell culture module, which allows the analysis of cells in the interior of scaffolds under different medium flow rates. For each flow rate the cell viability was measured and compared with results from computer simulations that predict the local oxygen supply and shear stress inside the scaffold based on the finite element method. We found that the local cell viability correlates with the local oxygen concentration and the local shear stress. On the one hand the oxygen supply of the cells in the core becomes optimal with a higher perfusion flow. On the other hand shear stress caused by high flow rates impedes cell vitality, especially at the surface of the scaffold. Our results demonstrate that both parameters must be considered to derive an optimal nutrient flow rate.

Hydraulic model of a water cooling system in a chemical plant

1988 ◽  
Vol 53 (4) ◽  
pp. 788-806
Author(s):  
Miloslav Hošťálek ◽  
Jiří Výborný ◽  
František Madron
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Cooling Water ◽  
Graph Algorithm ◽  
Automatic Generation ◽  
Hydraulic Calculation ◽  
Return Flow ◽  
Flow Rates ◽  
Pressure Losses ◽  
Controlled Flow

Steady state hydraulic calculation has been described of an extensive pipeline network based on a new graph algorithm for setting up and decomposition of balance equations of the model. The parameters of the model are characteristics of individual sections of the network (pumps, pipes, and heat exchangers with armatures). In case of sections with controlled flow rate (variable characteristic), or sections with measured flow rate, the flow rates are direct inputs. The interactions of the network with the surroundings are accounted for by appropriate sources and sinks of individual nodes. The result of the calculation is the knowledge of all flow rates and pressure losses in the network. Automatic generation of the model equations utilizes an efficient (vector) fixing of the network topology and predominantly logical, not numerical operations based on the graph theory. The calculation proper utilizes a modification of the model by the method of linearization of characteristics, while the properties of the modified set of equations permit further decrease of the requirements on the computer. The described approach is suitable for the solution of practical problems even on lower category personal computers. The calculations are illustrated on an example of a simple network with uncontrolled and controlled flow rates of cooling water while one of the sections of the network is also a gravitational return flow of the cooling water.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

scholarly journals Comparison of different models to calculate the viscosity of biogas and biomethane in order to accurately measure flow rates for conformity assessment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Karine Arrhenius ◽  
Oliver Büker
Keyword(s):  
Binary Mixtures ◽  
Flow Rate ◽  
Correction Method ◽  
Gas Mixtures ◽  
Conformity Assessment ◽  
Flow Rates ◽  
Unknown Composition

AbstractThe study presents an optimised method to correct flow rates measured with a LFE flowmeter pre-set on methane while used for gas mixtures of unknown composition at the time of the measurement. The method requires the correction of the flow rate using a factor based on the viscosity of the gas mixtures once the composition is accurately known. The method has several different possible applications inclusive for the sampling of biogas and biomethane onto sorbent tubes for conformity assessment for the determination of siloxanes, terpenes and VOC in general. Five models for the calculation of the viscosity of the gas mixtures were compared and the models were used for ten binary mixtures and four multi-component mixtures. The results of the evaluation of the different models showed that the correction method using the viscosity of the mixtures calculated with the model of Reichenberg and Carr showed the smallest biases for binary mixtures. For multi-component mixtures, the best results were obtained when using the models of Lucas and Carr.

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽  
2021 ◽  
pp. 1-5
Author(s):  
Jingjing Liu ◽  
Tengfang Chen ◽  
Zhenggang Lv ◽  
Dezhong Wu
Keyword(s):  
Flow Rate ◽  
Oxygen Therapy ◽  
Preliminary Investigation ◽  
Nasal Cannula ◽  
Low Flow ◽  
Antiplatelet Drugs ◽  
Flow Rates ◽  
The Past ◽  
Oxygen Inhalation ◽  
Significant Difference

<b><i>Introduction:</i></b> In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. <b><i>Methods:</i></b> We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. <b><i>Results:</i></b> No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ<sup>2</sup> = 1.007, <i>p</i> &#x3e; 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ<sup>2</sup> = 2.082, <i>p</i> &#x3e; 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate &#x3c;5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ<sup>2</sup> = 0.838, <i>p</i> &#x3e; 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ<sup>2</sup> = 18.428, <i>p</i> &#x3c; 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ<sup>2</sup> = 26.194, <i>p</i> &#x3c; 0.001). <b><i>Discussion/Conclusion:</i></b> Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

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