摘要:

Bubble size distributions in an airlift column were investigated with an emphasis on the downflow section. Measurements have been made using direct photographic techniques in conjunction with image analysis in a split cylinder airlift column. Information extracted from these measurements includes local gas hold-up, variation of Sauter mean bubble diameter with column length, and liquid circulation velocity. An air-tap water system was studied for purposes of comparison, while effects of electrolyte concentration and viscosity were studied using salt water, and two carboxymethyl cellulose (CMC) concentrations in water, respectively. The effect of energy input was studied by varying air flow rate to produce superficial velocities ranging from 2·59 cm/s to 10·36 cm/s.

ISSN:0098-6445    

DOI:10.1080/00986448608911343

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The transient floe size distribution in a lean, batch two phase dispersed system has been analyzed through Monte Carlo simulation. Two algorithms, SIMA and SIMB, have been investigated. The simulation results reveal that SIMA is suitable for portraying the breakage event which produces mainly small daughter particles while SIMB is capable of predicting the breakage event that produces a heavy-tailed daughter particle size distribution. Algorithm SIMA results in a positive correlation between parent particle size and the number of daughter particles produced upon breakage. The daughter particle size distribution is found to depend upon the size of the parent floe.

ISSN:0098-6445    

DOI:10.1080/00986448608911344

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The thermochemic method, where the catalyst temperature is manipulated by Joule-heating, may falsify the underlying kinetics by inducing inhomogeneous solutions. This work analyzes the multiplicity and stability of these states in a wire with uniform activity with or without gaps in heat conduction. Measurements of integral properties may indicate the existence of inhomogeneities either by the existence of characteristic multiplicity patterns and bifurcation maps or by unique quantitative features

ISSN:0098-6445    

DOI:10.1080/00986448608911345

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Ethylene oxidation to ethylene oxide and to carbon dioxide over silver catalysts was studied in a CSTR. The effects of two factors on the catalyst performance were examined. The first was the presence of excess ethylene oxide in the feed. A kinetic model was introduced which assumed that ethylene and ethylene oxide compete for the same sites on the catalyst surface. This model provided reasonable quantitative agreement with kinetic and potentiometric measurements. The second factor that was studied was the presence of external heat and mass transfer limitations. It was found that such limitations cause a significant decrease of the selectivity to ethylene oxide. This decrease is a result of the temperature difference between the catalyst surface and the bulk of the gas phase and of the fact that the activation energy of ethylene combustion is greater than that of ethylene epoxidation. The contribution of other factors such as inhibition by CO2or possible incomplete mixing in the reactor is shown to be insignificant.

ISSN:0098-6445    

DOI:10.1080/00986448608911346

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A scaled test facility of the Babcock & Wilcox raised loop nuclear steam supply system was used to perform small break loss-of-coolant accident testing, thereby, establishing a data base from which plant predictive system codes could be benchmarked. About 250 instruments were used to record the thermal/hydraulic response of the test facility during the transient, of which 36 were conductivity probes. These probes were designed and installed to determine the liquid-steam interface in the facility hot leg, reactor core vessel, and steam generator components

ISSN:0098-6445    

DOI:10.1080/00986448608911347

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Carnahan-Starling hard-sphere equation of state perturbed by attractive forces expressed in a virial expansion has been studied in the vicinity of the critical point. The three van der Waals conditions for the critical isotherm at the critical point were used to determine the minimum number of terms required in the perturbation series.P-v-Tdata at other temperatures were used for the determination of the temperature dependence of the virial terms. The equation has been tested for mixtures using the mixing rules of Araiet at.

ISSN:0098-6445    

DOI:10.1080/00986448608911348

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An approach originally developed to predict and correlate the thermophoretically-augmentedsubmicron particle mass transfer rate to cold surfaces is shown here to account extremely well for the thermophoreticallyreducedparticle mass transfer rate to “overheated” surfaces experiencing either a forced boundary layer (BL)-flow of laminar or turbulent dusty gas. This laminar BL/hot wall situation occurs, e.g., in hot surface/cold envelope chemical reactors used for growing epitaxial silicon layers from mainstreams containing, say, silane vapor and inadvertent submicron dust particles. “Thermo-phoretic blowing” is shown to produce effects on particle concentration BL-structure and wall mass transfer rates identical to those produced by real blowing (transpiration) through a porous wall. Indeed, a “blowing parameter additivity” relationship is proposed to account for the simultaneous effects of both phenomena should they be acting in concert (or in opposition). Exact numerical BL calculations covering the parameter ranges: l≤Tw/Te6, (particle thermophoretic-/gas thermal- diffusivity ratios between )0·1 and 0·8 and particle Schmidt numbers between 100and 2 × 103are used to establish the validity of the basic forced convection mass transfer correlations for self-similar laminar BLs and law-of-the-wall turbulent BLs. This includes parametric combinations of immediate engineering interest for which the deposition rate is thermophoretically reduced by no less than 10-decades! The applicability of our correlations todevelopingBL-situations is then illustrated using a numerical example relevant to wet-steam turbine technology.

ISSN:0098-6445    

DOI:10.1080/00986448608911349

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A new, highly porous silicon-based membrane was developed by pyrolyzing a silicon-rubber material (polydimethyl siloxane)in two steps. The first step was performed under an inert-gas environment below 800°C. The second step was performed in air below 950°C to oxidize and cross-link Si-O chains. The resulting silicon-based material was highly porous and had a fine pore structure (maximum porosity of 50%, BET surface area of I40m2/g) suitable for hot industrial gas separation even in a highly oxidizing environment. Gas permeability studies were performed at several different temperatures using a material derived by the pyrolysis of commercial silicon-rubber tubes. The results indicated that the flow through the membrane could be adequately explained by the Knudsen diffusion mechanism. The average permeabilities were 10 to 50 times those of porous Vycor glass.

ISSN:0098-6445    

DOI:10.1080/00986448608911350

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The hot-water coal drying process is a means of thermally beneficiating and dewatering lignite and subbituminous coal for the purpose of preparing dense low-rank coal/water fuel. In hot-water coal drying, which is a form of hydrothermal treatment, low-rank coal in a water slurry is treated at elevated temperatures of 513 to 623  K and at pressures in excess of the equivalent saturated steam pressures lo minimize vaporization of the water. This produces a coal product which contains less than one-third the inherent moisture of the raw coal and which is resistant to moisture reabsorption. The hydrothermally treated coal/water slurry resulting from the process can be concentrated by mechanical means (centrifuge, pressure filter)to form a pumpable coal/water fuel with greater than 60 weight percent bone-dry solids content and with an energy content greater than 15·4 MJ/Kg (6600 Btu/lb). Hydrothermal treatment also beneficiates the coal by reducing oxygen and minerals. Over 94 percent of the energy content of the raw coal remains in the product. Low-rank coal/water fuel is typically a pseudoplastic fluid, and for some low-rank coals, the slurry is stable towards settling, without the use of additives.

ISSN:0098-6445    

DOI:10.1080/00986448608911351

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The problem of determining the distribution of coke within a fixed bed catalytic reactor has been resolved by the non-invasive technique of neutron attenuation. Use of this technique has enabled the regeneration of the catalyst bed to be studied for different known coke distributions. Temperature profiles during regeneration are compared for different initial coke distributions.

ISSN:0098-6445    

DOI:10.1080/00986448608911352

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor