摘要:

AbstractBesides the knowledge of material constants of the homogeneous phases of a disperse system, a good understanding of its geometrical properties is necessary for describing physical processes. In order to characterize the shape of the interface between solids and pore space with respect to the irregularities in all orders of magnitude, the fractal dimension has proved to be an informative parameter. By this study the theory of fractal dimensions, in three‐dimensional space originally limited to topological curves, surfaces and volumes, is extended into physical properties like specific surface, tortuosity, porosity and formation factor with “physical” dimensions −1 or 0 as an exponent of the unit of length. The typical properties of the true fractals are transferable to some of these derived parameters. This leads to power laws describing the dependence of the particular measure on the resolution length. With special models, which seem to be of widespread validity in nature, petrophysical considerations lead to further power laws for the rest of the physical parameters, dependent on discrete length parameters such as grain radius and pore radius. By determination of the exponents of such independent power laws, a better particle characterization is possible, as the fractal dimension of the surface alone may be misleading, especially when the grain size of the particles is not

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010111

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe evaluation of particle size distributions of comminution products often shows that the experimental distributions cannot be represented by one of the well‐known functions (GGS, RRSB, log‐normal distributions). Although in some cases a more or less satisfactory approximation to one of these functions can be made, a physically meaningful interpretation is generally impossible. Using the frequency curve, it can often be shown that mixed distributions, represented by several statistical assemblies, do exist. In this paper the progeny size distributions of quartzite formed by slow compression comminution of single grains and particle beds as well as of the comminution products of a roller mill are interpreted as superpositions of several statistical assemblies each of which can be represented by a truncated log‐normal distrib

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010112

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe classification of powders into groups possessing specific behavioural identities has long been recognized as desirable. This has been approached by describing different powders using two variables and plotting the data on a scatter diagram. The property of interest is then inferred from a powder's position on the scatter diagram. Unfortunately, a powder's behaviour is rarely adequately described by only two variables. To describe a powder more fully requires more variables and this presents a problem in interpretation. Cluster analysis refers to a range of techniques for interpreting multivariate data sets and is used in many fields. This paper describes cluster analysis and considers the method and potential of its application to particle technology. By way of an illustration, a cluster analysis has been performed on twenty‐seven powders resulting in groups recognizable by their characteristic fluidisation and flow properties. It is concluded that cluster analysis could be a powerful tool in predictive and analytical work in the field of particle technolog

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010113

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractAn apparatus is described for the fast and automatic measurement of the grain size distribution of sand ranging from 0 to 4 mm. A sample of sand continuously introduced at a rate of 30 g/min is separated by the apparatus into seven fractions of 0–0.063, 0.063–0.125, 0.125–0.25, 0.25–0.5, 0.5–1, 1–2, and 2–4 mm. The amount of sand in each of these fractions is determined and the results are given in time intervals of 1 minute. The sand is separated in a separation chamber through which water streams in a horizontal laminar flow. The samples are separated according to their settling velocities. The four coarse fractions descend to the bottom of the chamber. They are collected and weighed under water. The three fine fractions remain suspended in three effluent water streams. The quantity of sand is measured in flow cells by absorption of laser light. Control of the system as well as the collection and processing of the measured data are done by means of an electronic control unit and a

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010114

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractWhile editing the first issues of Particle Characterization it has been recognized by the editors that the papers submitted differ widely in the representation of data and in the nomenclature chosen to characterize such common variables as particle size, different equivalent particle diameters, average particle sizes, cumulative and density values of a distribution etc. In oder to make papers published in this Journal more readily assimilable and graphs representing particle size analysis data instantly recognizable by using agreed upon standardized nomenclature the following paper has been submitted by one of the editors. It was first presented at the Harold Heywood Memorial Symposium, September 1974, at the University of Technology, Loughborough, U. K.

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010115

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe principle of an instantaneous reading, respirable dust, photometer and its application are described. The instrument measures the infrared light (940 nm wavelength) scattered on airborne particles under a mean scattering angle of 70°. Its open measuring chamber, which is insensitive to daylight, is filled with total dust. The photometer reading, however, is calibrated in terms of mass concentration of respirable dust by means of a gravimetric respirable dust sampler. Experiments carried out with monodisperse test aerosols and with real dusts confirm the instrument's principle. The photometer values obtained for real dusts can be linearly converted into mass values of respirable dust as long as ultra‐fine or ultra‐coarse dusts are excluded. In several practical cases an increased flux of scattered light is compensated for by a higher density of the dust mate

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010116

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractIn this paper a new electrical conductivity technique for the measurement of bubble size and velocity is presented. This measuring system is able not only to estimate size and velocity of particles (bubbles and droplets in liquids) but also to give complete information on the space related motion of particles. Thus a significant improvement is achieved in the accuracy of measurement.By using the simultanous measurement of both: bubble sizes and volumetric hold up of the dispersed phase, one is able to calculate the local interfacial area. In the first part of this paper the measuring system, its properties and limits are illustrated. In the second part results obtained in a bubble column will be presented.

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010117

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractIn optical particle counters the calibration function describing the relationship between the amplitude of the scattered light pulses and particle size depends on several parameters. In this paper, several calibration methods are discussed. As an example, the calibration of an optical particle counter (HC‐15, Polytec GmbH&Co., Waldbronn, FRG) is demonstrated, using real aerosols with unknown particle shape and refractive index, and a precollector with known collection efficiency. The error analysis, when performed together with the results of an indirect check of the obtained calibration curve, provide evidence that this method yields good calibration curves for the aerosol being measured. The method is then applied to obtain the calibration curves for quartz dust, ash from a fluidized bed combustor and coal dus

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010118

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe application of a new LDA method which simultaneously measures the size and velocity of small water droplets in the spray cone of a fan type water nozzle is described. As the phase difference between adjacent photomultipliers responding to signals from a fringe mode LDA is linearly proportional to the diameter of the spherical particle in the measuring volume, the new instrument allows, for long distances between the optical devices and the measuring volume in the spray, non‐invasive measurements and from these the correlation of size and velocity of the individual droplet in order to establish two‐dimensional distributions. From the new LDA instrument one receives definite information about the volume‐flow concentration in the measuring point of an enclosed flow situ

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010119

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasured drop‐size distributions are presented which were obtained by the atomization of water with hollow‐cone nozzles. The drop‐size distributions were determined using a scatteredlight particle size counting analyser at various locations in the droplet cone. These local distributions change systematically from the cone's axis to its border. To acquire the drop‐size distribution of all the drops the local distributions have to be superimposed. The spatial mass flow distribution in the cone can be calculated from these measu

ISSN:0934-0866    

DOI:10.1002/ppsc.19840010120

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY