Study of pumping effect in flow-through electrolysers

1983 ◽  
Vol 48 (8) ◽  
pp. 2232-2248 ◽  
Author(s):  
Ivo Roušar ◽  
Michal Provazník ◽  
Pavel Stuhl
Keyword(s):  
Natural Convection ◽  
Balance Equation ◽  
Volume Fraction ◽  
Industrial Applications ◽  
Pumping Effect ◽  
Flow Through ◽  
The Mean ◽  
The Difference

In electrolysers with recirculation, where a gas is evolved, the pumping of electrolyte from a lower to a higher level can be effected by natural convection due to the difference between the densities of the inlet electrolyte and the gaseous emulsion at the outlet. An accurate balance equation for calculation of the rate of flow of the pumped liquid is derived. An equation for the calculation of the mean volume fraction of bubbles in the space between the electrodes is proposed and verified experimentally on a pilot electrolyser. Two examples of industrial applications are presented.

Numerical Simulations of Particle-Laden Flow Based on Given Friction Reynolds Number and Mean Reynolds Number Respectively

2014 ◽  
Author(s):  
Zhenzhong Li ◽  
Jinjia Wei ◽  
Bo Yu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Wide Spectrum ◽  
Natural World ◽  
Industrial Applications ◽  
Particle Parameters ◽  
The Mean ◽  
The Difference ◽  
Particle Laden Flow

Multiphase flow with particles covers a wide spectrum of flow conditions in natural world and industrial applications. The experiments and the direct numerical simulation have become the most popular means to study the dilute particle-laden flow in the last two decades. In the experimental study, the mean Reynolds number is often adjusted to the value of single-phase flow for each set of particle conditions. However, the friction Reynolds number usually keeps invariable in the direct numerical simulation of the particle-laden flows for convenience. In this study the effect of the difference between given mean Reynolds number and friction Reynolds number was investigated. Two simulations were performed for each set of particle parameters, and the mean Reynolds number and friction Reynolds number were kept invariant respectively. From the results it can be found that the turbulence intensity and the dimensionless velocities are larger when keeping the friction Reynolds constant. And the results calculated from the cases of keeping the mean Reynolds number invariable agree with the experiment results better. In addition, the particle distribution along the wall-normal coordinate was found to be unchanged between two simulation conditions. As a suggestion, keeping the same mean Reynolds number in the direct numerical simulation of particle-laden flow is more appropriate.

scholarly journals Natural Convection over Two Superellipse Shapes with a Porous Cavity Populated by Nanofluid

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6952
Author(s):  
Noura Alsedais
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Darcy Number ◽  
Governing Equations ◽  
Porous Layers ◽  
Porous Cavity ◽  
The Mean ◽  
Volume Method

The influences of superellipse shapes on natural convection in a horizontally subdivided non-Darcy porous cavity populated by Cu-water nanofluid are inspected in this paper. The impacts of the inner geometries (n = 0.5,1,1.5,4) Rayleigh number (103 ≤ Ra ≤ 106), Darcy number (10−5 ≤ Da ≤ 10−2), porosity (0.2 ≤ ϵ ≤ 0.8), and solid volume fraction (0.01 ≤ ∅ ≤ 0.05) on nanofluid heat transport and streamlines were examined. The hot superellipse shapes were placed in the cavity’s bottom and top, while the adiabatic boundaries on the flat walls of the cavity were considered. The governing equations were numerically solved using the finite volume method (FVM). It was found that the movement of the nanofluid upsurged as Ra boosted. The temperature distributions in the cavity’s core had an inverse relationship with increasing Rayleigh number. An extra porous resistance at lower Darcy numbers limited the nanofluid’s movement within the porous layers. The mean Nusselt number decreased as the porous resistance increased (Da ≤ 10−4). The flow and temperature were strongly affected as the shape of the inner superellipse grew larger.

Moderate Reynolds number flows through periodic and random arrays of aligned cylinders

1997 ◽  
Vol 349 ◽  
pp. 31-66 ◽  
Author(s):  
DONALD L. KOCH ◽  
ANTHONY J. C. LADD
Keyword(s):  
Reynolds Number ◽  
Pressure Gradient ◽  
Volume Fraction ◽  
Unit Length ◽  
Reynolds Numbers ◽  
Moderate Reynolds Number ◽  
Random Arrays ◽  
Flow Through ◽  
The Mean ◽  
Square Array

The effects of fluid inertia on the pressure drop required to drive fluid flow through periodic and random arrays of aligned cylinders is investigated. Numerical simulations using a lattice-Boltzmann formulation are performed for Reynolds numbers up to about 180.The magnitude of the drag per unit length on cylinders in a square array at moderate Reynolds number is strongly dependent on the orientation of the drag (or pressure gradient) with respect to the axes of the array; this contrasts with Stokes flow through a square array, which is characterized by an isotropic permeability. Transitions to time-oscillatory and chaotically varying flows are observed at critical Reynolds numbers that depend on the orientation of the pressure gradient and the volume fraction.In the limit Re[Lt ]1, the mean drag per unit length, F, in both periodic and random arrays, is given by F/(μU) =k1+k2Re2, where μ is the fluid viscosity, U is the mean velocity in the bed, and k1 and k2 are functions of the solid volume fraction ϕ. Theoretical analyses based on point-particle and lubrication approximations are used to determine these coefficients in the limits of small and large concentration, respectively.In random arrays, the drag makes a transition from a quadratic to a linear Re-dependence at Reynolds numbers of between 2 and 5. Thus, the empirical Ergun formula, F/(μU) =c1+c2Re, is applicable for Re>5. We determine the constants c1 and c2 over a wide range of ϕ. The relative importance of inertia becomes smaller as the volume fraction approaches close packing, because the largest contribution to the dissipation in this limit comes from the viscous lubrication flow in the small gaps between the cylinders.

scholarly journals Enhancement of natural convection heat transfer in a U-shaped cavity filled with Al2O3-water nanofluid

2012 ◽  
Vol 16 (5) ◽  
pp. 1317-1323 ◽  
Author(s):  
Ching-Chang Cho ◽  
Her-Terng Yau ◽  
Cha’o-Kuang Chen
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Heated Wall ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
The Mean

This paper investigates the natural convection heat transfer enhancement of Al2O3-water nanofluid in a U-shaped cavity. In performing the analysis, the governing equations are modeled using the Boussinesq approximation and are solved numerically using the finite-volume numerical method. The study examines the effects of the nanoparticle volume fraction, the Rayleigh number and the geometry parameters on the mean Nusselt number. The results show that for all values of the Rayleigh number, the mean Nusselt number increases as the volume fraction of nanoparticles increases. In addition, it is shown that for a given length of the heated wall, extending the length of the cooled wall can improve the heat transfer performance.

Behavioral Toxicology of Organic Solvents. II. Comparison of Results on Toluene by Flow-Through and Closed Chamber Procedures

1983 ◽  
Vol 2 (4) ◽  
pp. 319-323 ◽  
Author(s):  
J. R. Glowa ◽  
P. B. Dews
Keyword(s):  
Organic Solvents ◽  
Appreciable Effect ◽  
Closed Chamber ◽  
Chamber Method ◽  
Comparison Of Results ◽  
Behavioral Toxicity ◽  
Flow Through ◽  
The Mean ◽  
The Difference ◽  
Closed Chamber Method

Concentration-effect curves for behavioral toxicity of toluene have been determined in 10 mice by a flow-through procedure. The mean of the estimates of concentrations of toluene which reduce responding by 50% is 2329 ppm and by 10% is 1523 ppm. The results are compared with previous determinations that used a closed-chamber procedure. The values then were 1806 ppm and 1299 ppm. The difference in the 2 estimates would have no appreciable effect on decisions on permissible concentrations based on the estimates so the greater simplicity of the closed-chamber method makes it worthy of consideration for routine purposes.

The Effect of Vocabulary Intervention on Text Comprehension: Who Benefits?

2019 ◽  
Vol 50 (4) ◽  
pp. 562-578 ◽  
Author(s):  
Dawna Duff
Keyword(s):  
Middle School ◽  
Reading Comprehension ◽  
Text Comprehension ◽  
Classroom Instruction ◽  
Vocabulary Instruction ◽  
Clinical Intervention ◽  
Vocabulary Knowledge ◽  
Vocabulary Intervention ◽  
The Mean ◽  
The Difference

Purpose Vocabulary intervention can improve comprehension of texts containing taught words, but it is unclear if all middle school readers get this benefit. This study tests 2 hypotheses about variables that predict response to vocabulary treatment on text comprehension: gains in vocabulary knowledge due to treatment and pretreatment reading comprehension scores. Method Students in Grade 6 ( N = 23) completed a 5-session intervention based on robust vocabulary instruction (RVI). Knowledge of the semantics of taught words was measured pre- and posttreatment. Participants then read 2 matched texts, 1 containing taught words (treated) and 1 not (untreated). Treated texts and taught word lists were counterbalanced across participants. The difference between text comprehension scores in treated and untreated conditions was taken as a measure of the effect of RVI on text comprehension. Results RVI resulted in significant gains in knowledge of taught words ( d RM = 2.26) and text comprehension ( d RM = 0.31). The extent of gains in vocabulary knowledge after vocabulary treatment did not predict the effect of RVI on comprehension of texts. However, untreated reading comprehension scores moderated the effect of the vocabulary treatment on text comprehension: Lower reading comprehension was associated with greater gains in text comprehension. Readers with comprehension scores below the mean experienced large gains in comprehension, but those with average/above average reading comprehension scores did not. Conclusion Vocabulary instruction had a larger effect on text comprehension for readers in Grade 6 who had lower untreated reading comprehension scores. In contrast, the amount that children learned about taught vocabulary did not predict the effect of vocabulary instruction on text comprehension. This has implications for the identification of 6th-grade students who would benefit from classroom instruction or clinical intervention targeting vocabulary knowledge.

Efficacy and Safety of Oral Ivermectin and Topical Permethrin in the Treatment of Scabies

2020 ◽  
Vol 33 (1) ◽  
pp. 41-47
Author(s):  
Mohsena Akhter ◽  
Ishrat Bhuiyan ◽  
Zulfiqer Hossain Khan ◽  
Mahfuza Akhter ◽  
Gulam Kazem Ali Ahmad ◽  
...  
Keyword(s):  
Skin Diseases ◽  
Close Contact ◽  
Randomized Study ◽  
Sarcoptes Scabiei ◽  
Efficacy And Safety ◽  
Common Skin ◽  
Group A ◽  
The Mean ◽  
The Difference ◽  
Group B

Background: Scabies is one of the most common skin diseases in our country. It is caused by the mite Sarcoptes scabiei var hominis, which is an ecto-parasite infesting the epidermis. Scabies is highly contagious. Prevalence is high in congested or densely populated areas. Individuals with close contact with an affected person should be treated with scabicidal which is available in both oral and topical formulations. The only oral but highly effective scabicidal known to date is Ivermectin. Amongst topical preparations, Permethrin 5 % cream is the treatment of choice. Objective: To evaluate the efficacy & safety of oral Ivermectin compared to topical Permethrin in the treatment of scabies. Methodology: This prospective, non-randomized study was conducted at the out-patient department of Dermatology and Venereology of Shaheed Suhrawardy Medical College & Hospital over a period of 6 months, from August 2016 to January 2017. The study population consisted of one hundred patients having scabies, enrolled according to inclusion criteria. They were divided into two groups. group A was subjected to oral Ivermectin and the group B to Permethrin 5% cream. Patients were followed up on day 7 and 14 for assessment of efficacy and safety. Result: The mean scoring with SD in group A (Ivermectin) and group B (Permethrin) were 8.26 ± 2.22 and 7.59 ± 2.01 respectively at the time of observation. The difference between the mean score of the two group is not significant (p=0.117) the mean scoring with SD in group A and group B were 4.54 ± 2.05 and 1.64 ± 1.84 respectively at 7thdays. The difference between the mean score of the two group is significant (p<0.001). The mean scoring with SD in group A and group B were 2.68± 2.35 and .36± 1.10 respectively at 14th day difference between the mean score of the group is significant (p<0.001). Conclusion: Topical application of permethrin 5% cream is more effective and safer than oral Ivermectin in the treatment of scabies. TAJ 2020; 33(1): 41-47

EFFECTS OF SYNTHETIC LH/FSH-RELEASING HORMONE (LRH) ON PLASMA LH AND FSH IN AMENORRHOEIC WOMEN

1974 ◽  
Vol 75 (4) ◽  
pp. 647-652 ◽  
Author(s):  
G. Rannevik ◽  
J. Thorell
Keyword(s):  
Urinary Excretion ◽  
Initial Response ◽  
Releasing Hormone ◽  
The Mean ◽  
The Difference ◽  
Serial Measurements

ABSTRACT Eight amenorrhoeic women were given 100 μg synthetic LRH (Hoechst) iv and im, respectively, at an interval of 2 weeks. Four of the women received the iv injection first and four the im injection. The urinary excretion of oestrogens and pregnanediol was low and unaltered throughout the test weeks. The effects of LRH were compared by serial measurements of the plasma LH and FSH during 8 h. The initial response of LH for up to 25 min and that of FSH for up to 60 min were equal whether LRH was given iv or im. The difference appeared later. Four hours after the injection the mean increase of LH to iv injection was 0.5 ng/ml (N. S.), while that to im injection was 1.9 ng/ml (P < 0.01). The corresponding values for FSH were 1.3 (P < 0.05) and 3.2 (P < 0.001). The effect of LRH administration im was thus found to be larger and more prolonged.

Development of Prolonged Delivery of Tramadol and Dissolution Translation by Statistical Data Treatment

2011 ◽  
Vol 4 (1) ◽  
pp. 1331-1337
Author(s):  
P B Parejiya ◽  
B S Barot ◽  
P K Shelat
Keyword(s):  
Drug Release ◽  
Study Data ◽  
Stability Study ◽  
Dissolution Time ◽  
Matrix Tablet ◽  
Burst Effect ◽  
The Matrix ◽  
The Mean ◽  
The Difference ◽  
Dissolution Efficiency

The present study was carried out to fabricate a prolonged design for tramadol using Kollidon SR (Polyvinyl acetate and povidone based matrix retarding polymer). Matrix tablet formulations were prepared by direct compression of Kollidon SR of a varying proportion with a fixed percentage of tramadol. Tablets containing a 1:0.5 (Drug: Kollidon SR) ratio exhibited a rapid rate of drug release with an initial burst effect. Incorporation of more Kollidon SR in the matrix tablet extended the release of drug with subsequent minimization of the burst effect as confirmed by the mean dissolution time, dissolution efficiency and f2 value. Among the formulation batches, a direct relationship was obtained between release rate and the percentage of Kollidon SR used. The formulation showed close resemblance to the commercial product Contramal and compliance with USP specification. The results were explored and explained by the difference of micromeritic characteristics of the polymers and blend of drug with excipients. Insignificant effects of various factors, e.g. pH of dissolution media, ionic strength, speed of paddle were found on the drug release from Kollidon-SR matrix. The formulation followed the Higuchi kinetic model of drug release. Stability study data indicated stable character of Batch T6 after short-term stability study.

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