摘要:

AbstractThis paper describes a preliminary experimental study of the sliding friction of sand‐water mixtures when continuously propelled over glass surfaces by a potential energy gradient. The particle contact density at the glass wall and the work dissipated are estimated. These experiments are compared with the process of hydraulic conveying of sand‐water mixtures under a hydraulic gradient. It is argued that there is a unique correlation between the surface particle density and the frictional work irrespective of the nature of the driving force. This argument allows a realistic estimate of the frictional work in hydraulic conveying to be made from the measurement of surface particle velocity during flow. In an example cited, the dynamic coefficient of sliding fraction for a particular case of sand‐water flow is found to be a function of mean velocity and decreases from about 0.65 to 0.22 for velocities of 0.47 and 1.07 m/s respect

ISSN:0008-4034    

DOI:10.1002/cjce.5450610601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractParticle capture experiments conducted in turbulent cross flow with various aerosols involving liquid and/or solid particulates have resulted in collection efficiencies which are in excess of the values predicted by the various known models of particle capture, i.e., inertial impaction, interception and Brownian diffusion.In one type of experiment the turbulent air stream, carrying submicron dust particles, is flowing past a cylindrical collector (such as a piece of wire) with its axis orientated perpendicular to the direction of flow. Collecting efficiencies ranging up to about 20% have been found under conditions where the conventional models of particle capture predict practically zero collection efficiencies.In another type of experiment involving injecting a fog (2–80 μm diameter water droplets) into the dusty gas stream carrying submicron size dust particles which subsequently enters a slow turning fan. While passing through the fan, the fog agglomerates into raindrops while scavenging most of the dust particles. For example, a 0.8 μm median particle size aluminum silicate pigment was collected with 97–99.5% efficiency, the exact value depending on the operating conditions.Theoretical analysis of these phenomena may be based on the idea of synergism involving inertial impaction and eddy diffusion: the smaller dust particles/drops are captured by the larger drops in the fan and the dust particles are captured by the wires because (a) there is a significant relative velocity between them and (b) because the particles undergo eddy diff

ISSN:0008-4034    

DOI:10.1002/cjce.5450610602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe rheological properties of brown coal‐oil suspensions were investigated using both a Contraves rheometer and a Weissenberg rheogoniometer. The aging characteristic of the suspensions was found to be due to the moisture in the coal and the presence of large numbers of micropores. Moisture in the suspension caused aggregation of coal particles and diffusion of oil in the pores was responsible for the reduction in the volume fraction of free carrier oil. Both the yield stress and apparent viscosity were found to increase sharply if the coal contained more than 10 wt% moisture. Photomicrographs were also used to identify the cause of aggregation in brown coal‐oil suspensi

ISSN:0008-4034    

DOI:10.1002/cjce.5450610603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractHeat and mass transfer in laminar and turbulent non‐Newtonian fluids is investigated in this work using the power function velocity profiles. Analytical solutions are presented for cases of mass transfer in laminar non‐Newtonian fluid flows, namely for a flat velocity profile (plug flow), for the case of a constant velocity gradient at the solid boundary (Couette flow), and for the velocity distribution within a laminar boundary layer on a flat plate, and these are illustrated by rotating disks and cylinders in laminar Ostwald‐de Waele fluids. Further, turbulent mass transfer processes (tubular flow, rotating disk, and rotating cylinder) in non‐Newtonian fluids (Ostwald‐de Waele fluid and drag‐reducing fluid) at low and large Schmidt numbers are also discussed using the solutions of mass transfer in flows with power function velocity profiles. Reasonable agreement is found between the predictions of this work and the available experimental data and c

ISSN:0008-4034    

DOI:10.1002/cjce.5450610604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractExperiments were carried out to measure the Henry's law constant for HCN in solutions from the cyanidation of zinc concentrate. The measured value for zinc thickener underflow solution was 5.0 atm/mole fraction whereas for synthetic leach solutions and pure cyanide solutions it was 6.1 and 6.4, respectively. Pilot plant stripping tests were carried out using a 0.3 m diameter column operated under full‐scale hydrodynamic conditions to measure the mass transfer coefficient and also to study the potential scaling problem due to the precipitation of gypsum and CuCNS. These data were used to design the full‐scale plant in a silver recovery flowsh

ISSN:0008-4034    

DOI:10.1002/cjce.5450610605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractIn addition to the two different condensation patterns revealed respectively inn‐pentane (bubble)/glycerol and water (bubble)/silicone oil systems in the authors' previous study (1979), a third pattern has been found in methanol (bubble)/silicone oil system: a condensate appears at the rear part of the bubble surface as several blunt drops, turns into a conical tail through coalescence to each other, and finally drops out from the bubble. The possible mechanism as well as the heat transfer characteristics of the condensation process are discusse

ISSN:0008-4034    

DOI:10.1002/cjce.5450610606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractAn experimental programme for batch and continuous sedimentation was planned to study the feasibility of increasing the rate of sedimentation of the causticized slurry obtained with gypsum as make‐up salt in a Kraft recovery cycle. The studies were conducted in tubular clarifier under vertical and inclined conditions.For batch sedimentation studies, attempts were made to make a comparative evaluation of existing models. A good agreement was observed with the effective width concept model. The presence of unreacted gypsum in the causticized slurry favours the rate of sedimentation.For continuous sedimentation studies, enhancement factor variation was observed from 1.39 to 4.20 under inclined conditions at steady stat

ISSN:0008-4034    

DOI:10.1002/cjce.5450610607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe method of Lagrangian multipliers of classical calculus is applied to obtain the optimum operating conditions of three continuous stirred tank reactors (CSTR) in series, to liquefy coal with minimum gas yield. In the formulation of the problem, the gas conversion was assumed to be the cost function. Results obtained were supported by the experimental findings in terms of liquefaction temperatures, reaction times, and conversion of coal into various liquefaction products.

ISSN:0008-4034    

DOI:10.1002/cjce.5450610608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractStudies have been carried out at 2.38 MPa total pressure and at 360 and 400°C of the synthesis of ammonia over a triply‐promoted iron catalyst (United Catalysts Inc.). Runs were carried out using a gradientless reactor in steady‐state and periodic modes, the latter employing forced composition cycling. The catalyst had a particle diameter of 0.30 mm; the resulting reaction rates were free from transport intrusions. The range of mean compositions for steady‐state measurements was from 0.1 to 0.9 mole fraction of hydrogen and for periodic operation from 0.5 to 0.9. The cycle‐split ratio (used to describe non‐uniform cycling) varied from 0.2 to 0.85. Effects of cycle period, mean composition, cycle‐split, and temperature were investigated. Instantaneous rate variations within the cycle are reported.Results showed that the cycling mode of operation results in an improvement in the time‐average rate of ammonia formation of up to 30%, depending upon the choice of operating parameters. Some implications for the mechanism of ammonia synthesis under periodic operation

ISSN:0008-4034    

DOI:10.1002/cjce.5450610609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe selective recovery of vanadium from an effluent of a manufacturing process for titanium white (oxide) has been made. The process retained is based on the partial neutralization of the effluent by means of calcium carbonate and on the separation of metal hydroxides from calcium sulfate and the solution. The hydroxides are thereafter calcined in the presence of a sodium salt, so that sodium vanadate may then be extracted by washing with water. Vanadium is finally precipitated by the addition of ammonium chloride or pH adjustment.The experimental results obtained in the laboratory study of the effluent neutralization, the calcination and leaching of the hydroxides and the vanadium precipitation are presented and discussed. The yields obtained in the various stages and their interdependance are also discussed.

ISSN:0008-4034    

DOI:10.1002/cjce.5450610610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY