Volume Flow Rate Ratio Research Articles

Investigations into aggregate formation with oppositely charged oil-in-water emulsions at different pH values

The pH-dependent formation and stability of food-grade heteroaggregates from oppositely charged oil-in-water (O/W) emulsions was investigated. After screening suitable emulsifiers, 10% (w/w) oil in-water emulsions (d32≈1μm) were prepared at pH 3–7 using a positively charged emulsifier (Na-lauroyl-l-arginine ethyl ester; LAE) and four negatively charged ones (citric esters of mono- and diglycerides, soy lecithin, sugar beet pectin, and Quillaja saponin). The oppositely charged emulsions were then combined at constant pH values at a volume flow rate ratio of 1:1. Emulsions and heteroaggregates were characterized by their surface charge, particle size distribution and microstructure using dynamic and static light scattering as well as confocal laser scanning microscopy. The emulsifier type was found to greatly influence the type of heteroaggregates formed, as well as the pH value, specifically in combined LAE/Quillaja saponin emulsions. Larger aggregates particularly were formed with increasing pH values (2.71±1.21 to 46.53±4.30μm from pH 3 to 7, respectively), while LAE/pectin aggregates appeared not to be affected by pH over the full pH range investigated (3.80±2.89 to 3.94±2.78μm from pH 3 to 7, respectively). Our study thus provides valuable first insights into the mechanism of the formation of food-grade heteroaggregates for later use in food systems.

Effect of uneven red cell influx on formation of cell-free layer in small venules

This study examined how the uneven influx of red blood cells (RBCs) from feeding vessels influences formation of cell-free layer (CFL) in the downstream vessel of a venular bifurcation. Spatio-temporal variations of the CFL width along the downstream vessel (19–41-μm inner diameter, D) were determined at 0.5D intervals from 0.5D to 3.0D away from the bifurcation. Upstream flow conditions were quantified by the ratio of volume flow rates (Q⁎=QHigh/QLow) between high flow (QHigh) and low flow feeding (QLow) vessels. The RBC aggregation level in the rats was adjusted to be at healthy human levels by infusing Dextran 500. Our results suggested that the CFL formation process could be seen only from 2.0D away from the bifurcating point. The mean CFL width at the wall adjacent to the feeding vessel with a higher flow rate was consistently greater than that at the opposite wall, leading to an asymmetric CFL formation in the vessel. A positive relation (P<0.05) between the asymmetry of the CFL width and the volume flow rate ratio (Q⁎) was found. Our numerical prediction showed that flow resistance in the venular network could be significantly increased by the asymmetric formation of CFL downstream and this effect might become more pronounced under pathological flow conditions such as hyper-aggregating and/or low shear conditions.

Impact of Structure Design of Artififical Upwelling Tube

Deep ocean water (DOW) is cold, nutrient-rich and pathogen-free water, which can be transported to the surface by upwelling. Upwelling can change the temperature and nutrient distribution of the surrounding water, hence improves the marine ecological environment and the marine primary productivity. Two lake experiments were accomplished in Qiandao Lake .The first experiment was done with hard PVC upwelling tube, while in the second experiment , the upwelling tubes with different diameters (0.5 m, 1 m, 1.5 m and 2 m) were made of nylon ,which are supported by rings. It can be concluded that upwelling ratio (the ratio of water volume flow rate and air volume flow rate) of the hard PVC upwelling tube was higher than that of soft nylon upwelling tube, and in condition of soft nylon upwelling tube, upwelling ratio of 1 m diameter tube was higher than that of others, providing important guidance for the next sea trial.

Liquid–liquid extraction based on droplet flow in a vertical microchannel

In this work, the flow patterns and mass transfer characteristics of immiscible fluids based on droplet flow in a vertical microchannel are investigated experimentally. Water-succinic acid-n-butanol is chosen for the working system. An opposite-flowing T-shaped microchannel has been proposed to form favourable monodispersed droplet flow in a wide range of volume flow rate ratio. Experiments were performed at volume flow rate ratios between 1.2 and 24, and droplet flow and plug flow were observed in the main channel. The droplet flow occurs at volume flow rate ratio of 3–24, and plug flow occurs at volume flow rate ratio of 1.2–2. For droplet flow regime, monodispersed organic droplets with average diameters of 123–532μm were generated, and the volumetric mass transfer coefficients were in the ranges of 0.012–0.082s−1. In addition, the effects of various operating conditions such as volume flow rate ratio, total flow velocity, and the inner diameter of the main channel on the droplet coalescence, average droplet diameter, extraction efficiency and volumetric mass transfer coefficient are also been studied. An empirical correlation is developed to predict the volumetric mass transfer coefficients.

Experimental study of heat transfer enhancement in electrohydrodynamic conduction pumping of liquid film using flush electrodes

Electrohydrodynamic conduction pumping of free surface dielectric liquid film, using flush electrodes, has been studied experimentally for various film temperatures. Volume flow rate, heat transfer and power consumption ratio and conduction pumping efficiency of free surface liquid film in different film thicknesses and temperatures have been investigated and then the best operating conditions have been presented. Also, the heat transfer coefficient on free surface liquid film passing on flush electrodes is compared with similar liquid film in absence of flush electrodes in different temperatures. Results show that as applied voltage increases, significant differences in volume flow rates have been observed by changing the temperature. Applied voltage related to the highest percentage of heat transfer coefficient enhancement demonstrates the reverse relation with temperature. Results confirm that there is a direct relationship between film thickness and the applied voltage related to the maximum heat transfer per pumps power consumption.

Catalytic Oxidation of Toluene over CuyMnzOx/γ-Al2O3 Catalysts

Experimental investigations using granular activated carbon (GAC) adsorption and then desorpted with microwave irradiation for toluene abatement are reported in this paper. The results indicated that For different kinds of catalysts, Cu0.33Mn0.67Ox/γ-Al2O3 had the highest catalytic activity. For toluene combustion, the temperature required for 99% toluene conversion was lower than 300°C. In combination process of microwave desorption with catalytic combustion, the toluene conversion was ranged from 92% to 99% and the optimum volume flow rate ratio of carrier and air was 1:1.

Catalytic Oxidation of Toluene over Cu&lt;sub&gt;y&lt;/sub&gt;Mn&lt;sub&gt;z&lt;/sub&gt;O&lt;sub&gt;x&lt;/sub&gt;/γ-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Catalysts

Experimental investigations using granular activated carbon (GAC) adsorption and then desorpted with microwave irradiation for toluene abatement are reported in this paper. The results indicated that For different kinds of catalysts, Cu0.33Mn0.67Ox/γ-Al2O3 had the highest catalytic activity. For toluene combustion, the temperature required for 99% toluene conversion was lower than 300°C. In combination process of microwave desorption with catalytic combustion, the toluene conversion was ranged from 92% to 99% and the optimum volume flow rate ratio of carrier and air was 1:1.

Hemodynamics in the pulmonary artery of a patient with pneumothorax

Pneumothorax is characterized by lung collapse and an alteration of lung geometry, resulting in alterations of the pulmonary artery blood flow. Though many clinical studies and animal experiments have investigated the effects of pneumothorax on the hemodynamics of pulmonary arteries, its precise effects remain unclear. In this patient-specific study, we investigated the effects of lung deformation and vascular resistance increases due to pneumothorax on the pulmonary blood flow during the acute phase and after recovery. Arterial geometry was extracted up to the fifth generation from computed tomography images, and reconstructed. Computational fluid dynamic analysis was performed, for an unsteady laminar flow with resistance at the outlets, in a reconstructed domain. The results demonstrated a change in flow structure during systole between the acute phase and recovery, and were associated with variations in the flow rate ratio between the right and left lungs. We observed a parabolic-like decrease of the volume flow rate ratio in the affected lung as the resistance increased. Thus, the systemic artery blood oxygenation will rely more on the unaffected lung leading to improved oxygenation of the blood under high resistance in the affected lung. These findings are significant in our understanding of ventilation function under a pneumothorax.

Effect of flip angle on volume flow measurement with nontriggered phase‐contrast MR: In vivo evaluation in carotid and basilar arteries

To evaluate the effect of flip angle on volume flow rate measurements obtained with nontriggered phase-contrast magnetic resonance imaging (MRI) in vivo. We prospectively measured volume flow rates of the bilateral internal carotid artery and the basilar artery with cine and nontriggered phase-contrast MRI. For nontriggered phase-contrast imaging, flip angles of 4, 15, 60, and 90 degrees were used for 40 volunteers and of 8, 15, and 30 degrees for 54 volunteers. Lumen boundaries were semiautomatically determined by pulsatility-based segmentation using cine phase-contrast MRI. Identical lumen boundaries were used for nontriggered phase-contrast imaging. The ratio of volume flow rate obtained with nontriggered phase-contrast imaging to that obtained with cine phase-contrast imaging significantly increases with an increase in the flip angle. The mean ratios lie within a relatively narrow range of +/-15% with a wide range of flip angles of 8-90 degrees . As the flip angle increases, ghost artifacts become prominent and signal-to-noise and contrast-to-noise ratios increase. Flip angles between 8 and 60 degrees are most appropriate for nontriggered phase-contrast MR measurements in the internal carotid and the basilar artery.

Microstructure and Characteristics of Thin-Film La0.8Sr0.2Co0.5Ni0.5O3/ZnO:Al Heterocontact CO Sensors Prepared by RF Magnetron Sputtering

Highly sensitive CO gas sensors based on heterocontacts of ZnO:Al on La0.8Sr0.2Co0.5Ni0.5O3 (LSCNO) were fabricated successfully. La0.8Sr0.2Co0.5Ni0.5O3 thin films were coated on (100) silicon wafers by a sol-gel method including the Pechini process followed by a spin-coating procedure. Then, ZnO:Al films prepared by radiofrequency (RF) magnetron sputtering at various oxygen partial pressures and deposited on as-deposited La0.8Sr0.2Co0.5Ni0.5O3 films were investigated. The results revealed that the CO sensing ability of the film prepared with the ratio of O2/Ar = 5/5 (ratio of volume flow rate) was the worst, owing to the highest (002) plane orientation in the ZnO:Al film. In contrast, the ZnO:Al film prepared with O2/Ar = 3/7 exhibited better CO sensitivity. Furthermore, all two-layer samples showed higher CO sensitivities than single-layer samples. The CO sensitivity of ZnO:Al/La0.8Sr0.2Co0.5Ni0.5O3 thin film was 45% for 500 ppm CO at a sensing temperature of 200°C.

Density stratified environments: the double-tank method

We present an alternative method of producing density stratifications in the laboratory based on the ‘double-tank’ method proposed by Oster (Sci Am 213:70–76, 1965). We refer to Oster’s method as the ‘forced-drain’ approach, as the volume flow rates between connecting tanks are controlled by mechanical pumps. We first determine the range of density profiles that may be established with the forced-drain approach other than the linear stratification predicted by Oster. The dimensionless density stratification is expressed analytically as a function of three ratios: the volume flow rate ratio n, the ratio of the initial liquid volumes λ and the ratio of the initial densities ψ. We then propose a method which does not require pumps to control the volume flow rates but instead allows the connecting tanks to drain freely under gravity. This is referred to as the ‘free-drain’ approach. We derive an expression for the density stratification produced and compare our predictions with saline stratifications established in the laboratory using the ‘free-drain’ extension of Oster’s method. To assist in the practical application of our results we plot the region of parameter space that yield concave/convex or linear density profiles for both forced-drain and free-drain approaches. The free-drain approach allows the experimentalist to produce a broad range of density profiles by varying the initial liquid depths, cross-sectional and drain opening areas of the tanks. One advantage over the original Oster approach is that density profiles with an inflexion point can now be established.

Performance characteristics of the hybrid closed circuit cooling tower

Experimental study on the hybrid closed circuit cooling tower (HCCCT) has been done having a rated capacity of 136 kW. Bare-type copper coil having an outer diameter of 15.88 mm has been used in the 1.14 m × 2.36 m × 3.2 m dimensional tower. Cooling capacity and pressure drop have been studied with respect to variable air inlet velocities, wet-bulb temperatures, cooling water inlet temperatures and air to cooling water volume flow rate ratio (G/W ratio). Performance characteristics from the experimental study were found to conform well to the rated ones. The results are supposed to serve as basic design parameter for the HCCCT.

Optimal design of an integrated fermentation process for lactic acid production

AbstractIn this work, we considered a multistage integrated continuous fermentation process for producing lactic acid. Each stage consists of a mixing tank, a bioreactor, a cell‐recycle unit, and an extractor. A generalized mathematical model was formulated to express the integrated process. We have compared the overall productivity and conversion of the integrated process with those of two simplified processes. From the design equations, three processes have an identical overall conversion. However, the proposed process has the greatest overall productivity. A specific kinetic model for lactic production was applied to the integrated process to formulate it as a flexible or fuzzy optimization problem to find the maximum overall productivity and conversion with interval residual and supplied glucose constraints. Four optimization problems were considered to determine the optimal stages, operating conditions, and design variables. If the decision variables excluded the working volume ratio and flow rate ratio in the optimization problem, four stages were required to yield the maximum overall productivity and near complete overall conversion. However, if both operation variables were considered as the decision variables in the optimization problem, three stages were sufficient to achieve the identical overall productivity. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Effects of implantation temperature and volume flow rate ratio of nitrogen and hydrogen on nitrogen concentration distribution, mechanical properties, fatigue life, fracture toughness, and tribological behavior of plasma-nitrided P20, 718 and 420 steels

In the present study, three steel materials, AISI P20 DEM NO.3, ASSAB 718 and AISI 420, were selected as the mold substrate materials in plastic injection forming. The plasma immersion ion implantation (PIII) system with an electron cyclotron resonance microwave source was applied to prepare the specimens by varying the implantation temperature (400 °C, 460 °C and 520 °C) and the volume flow rate ratio (4:1, 1:1 and 1:3) of nitrogen to hydrogen in the gas mixture (N 2:H 2). For the specimens with the same substrate material, the mean hardness was either invariant to or lowered by increase in the total penetration depth of nitrogen. The hardness was lowered by increasing the distance of the peak position of nitrogen concentration from the implantation surface. Both the fracture toughness and the fatigue life of a specimen at the nitrided layer were elevated by increasing the implantation temperature. The most significant increase in each of these two mechanical properties due to the temperature increase gives rise in the P20 specimens. Varying the N 2:H 2 ratio shows a fatigue life sequence of (FL) 4:1 > (FL) 1:3 ≥ (FL) 1:1 for all three substrate materials. X-ray diffraction (XRD) was applied to determine the phase structures at the nitrided layer which was formed by changing either the implantation temperature or the N 2:H 2 ratio. The (α-Fe + CrN) phase in the nitrided later can elevate the fatigue life and fracture toughness of the specimen. However, the increase in the hardness is due to the combined effect of all main phases formed in the nitrided later. The scratch wear resistance of a specimen with ion implantations is significantly enhanced compared with that exhibited in the “pure” specimen (without nitrided layer). However, most of the specimens with ion implantations showed severer adhesive wear than corresponding “pure” specimens.

Development of a large-entrainment-ratio axisymmetric supersonic ejector for micro butane combustor

A large-entrainment-ratio micro ejector has been developed to supply fuel–air mixture for a micro butane combustor. As a key component of the ejector, an axisymmetric convergent–divergent supersonic nozzle having a throat diameter of 42 µm is fabricated with high-precision electro-discharge machining. Operating conditions and geometric parameters of the ejector are systematically changed, and their effects on volume–flow-rate ratio are investigated in a series of experiments. Experimental data are compared with analytic solutions and CFD results. It is found that the present micro ejector achieves a maximum air-to-butane volume–flow-rate ratio of 43 when the back pressure is 11.6 Pa. It is also found that the present ejector can produce larger volume–flow-rate ratio than the previous MEMS 2D ejector at small back pressure.

Volume Flow Rate of Common Carotid Artery Measured by Doppler Method and Color Velocity Imaging Quantification (CVI-Q)

Common carotid artery (CCA) volume flow rate (VFR) is clinically useful for study of cerebrovascular disease. Color Velocity Imaging Quantification (CVI-Q; Philips Ultrasound International, Irvine, CA), previously reported as accurate and reliable, tracks the flow lumen over the cardiac cycle, as well as mean spatial velocity, which is multiplied by vessel area to obtain VFR. VFR can also be obtained by Doppler sampling for mean velocity, and vessel area based on static B-mode lumen diameter. We compared CCA VFR by CVI-Q and Doppler method (DM), since knowledge of how they compare is crucial when both are used clinically. We prospectively studied patients having clinical carotid duplex exams and healthy controls. All had CCA VFR measured by both methods in the same exam session. Thirty-four studies were reviewed. CCA VFR by CVI-Q in those without ICA stenosis was 337 +/- 96 mL/m, and by DM 359 +/- 130 mL/m; P = .33. There was no difference between methods for 50-75% or 75-95% ICA stenosis. In 7 patients with ICA occlusion, and 3 with 95-99% stenosis, VFR was higher by DM than by CVI-Q (Occlusion: 125 vs 58 mL/m, P = .007; 95-99%: 152 vs 63 mL/m, P = .038). There was no statistically significant difference between methods for measurement of the ratio of VFR between right and left CCA. In patients with 0-95% ICA stenosis, VFR by CVI-Q and DM showed no difference. For 95-100% ICA stenosis the methods differ; with higher VFR by DM. Side-to-side VFR ratios remain constant, irrespective of VFR method, and can still provide clinically useful information.

Gas flow characteristics in straight silicon microchannels

Experiments have been conducted to investigate nitrogen gas flow characteristics through four trapezoidal silicon microchannels with different hydraulic diameters. The volume flow rate and pressure ratio are measured in the experiments. It is found that the friction coefficient is no longer a constant, which is different from the conventional theory. The characteristics are first explained by the theoretical analysis. A simplified rectangular model (rectangular straight channel model) is then proposed. The experimental results are compared with the theoretical predictions based on the simplified rectangular model and the two-dimensional flow between the parallel-plate model which was usually used. The difference between the experimental data and the theoretical predictions is found in the high-pressure ratio cases. The influence of the gas compressibility effect based on the Boltzmann gas kinetic analysis method is studied to interpret the discrepancy. We discuss two important factors affecting the application extent of different prediction models.

Sensitivity Analysis of Hole Cleaning Parameters in Directional Wells

SummaryIn this study, 600 tests were conducted and a new computer program was developed for the prediction of cuttings transport in the multiphase system (gas+liquid+cuttings). The sensitivity of cuttings bed height with respect to liquid/gas volume flow rate ratio, in-situ liquid velocity, rate of penetration (ROP), inclination angle, and circulation fluid properties was conducted. The hole-cleaning time with both circulation mode and wiper trip is also discussed. The results from the sensitivity analysis presented in this paper indicate, first, that the fraction of the circulation liquid has a significant impact on the cuttings transport in underbalanced drilling with gasified fluids; second, that among different variables, the in-situ liquid velocity is the most important variable for cuttings transport; and, finally, the hole-cleaning time decreases nonlinearly with increasing fluid circulation rate.

Increase MeOAc conversion in PVA production by replacing the fixed bed reactor with a catalytic distillation column

Catalytic distillation (CD) technology in hydrolyzing methyl acetate (MeOAc) in polyvinyl alcohol (PVA) production process was studied in this paper. Three operational variables, R m -mole ratio of feed water to MeOAc, R f -volume ratio of reflux to feed MeOAc and S V -the ratio of the feed volume flow rate of MeOAc to the volume of catalyst bed, are defined and investigated in detail. Two parameters, R con, the conversion of MeOAc, and R A/ W , the mass ratio of acetic acid to water in the hydrolysis mixture are also defined. They are used as indices for investigating the performance of the catalytic distillation. As a strong industrial backgrounded project, there is a premise that must be satisfied, that is the R A/ W cannot be less than 1.3. According to the experimental results, a set of operational parameters is recommended. The R m ranges from 2 to 3, the R f ranges from 3.0 to 5.5 and the S V from 0.25 to 0.55. With the satisfaction of the R A/ W , the conversion of MeOAc by CD technology is as high as 56%, which is more than two times that of the fixed bed reactor (FBR) technology. If the R A/ W is not taken into account, complete conversion of MeOAc can be achieved easily with a high R m .

Numerical Analysis of Wells Turbine Aerodynamics

Ocean wave power can be harnessed by means of a Wells turbine driven by a bi-directional airflow above an oscillating water column. While the Wells turbine research budget remains small, full-scale experiments are prohibitively expensive. Computational fluid dynamics (CFD) is a possible way of generating full-scale data. This paper summarizes a numerical study of Wells turbine performance and aerodynamics using a CFD method, and makes recommendations about its use for Wells turbine studies. Calculations have been performed for a monoplane turbine comprised of straight NACA 0015 blades at a stagger angle of 90 deg, Reynolds number 8 x 105, tip Mach number 0.4, and hub-to-tip ratio 0.6. Flow coefficient, tip clearance, and blade number were varied. The predictions agree favorably with experimental data. Differences can be explained partly by geometric differences between the experimental and numerical turbines. Because of the 90-deg stagger angle of the turbine, accurate predictions require fine resolution of the blade leading-edge region. This makes performance calculations expensive, and it is probably more prudent to use simpler predictive methods. CFD, however, is most useful for the study of turbine aerodynamics. Nomenclature CT = torque coefficient c - blade chord h = ratio of hub diameter to tip diameters N = number of blades in annulus p^ p 2 = static pressure up- and downstream of turbine Q = volume flow rate QR - volume flow rate ratio Rt - tip radius of turbine T = torque Ut = blade tip velocity Vx = axial velocity Ap* = nondimensional ized pressure drop j] = efficiency 6 = tangential coordinate cr = turbine solidity, Ncl[7rRt( + h)] TC = blade clearance at tip as percentage of chord 4> = flow coefficient fl = angular velocity of turbine