A laser diffraction system was used to obtain the history of the Sauter mean diameter of an evaporating fuel spray. The errors due to the characteristic properties of the laser diffraction method were examined by using many kinds of sprays. Then, the application procedure was established by using a micro-computer system. The sectional Sauter mean diameter was introduced to examine the overall evaporation rate of a spray in hot air. The Sauter mean diameter of gasoline, kerosene and heavy oil sprays were measured. The Sauter mean diameter of an evaporating spray increased once and decreased at the end of the evaporation.
The results of the particle size measurements by several methods based on different principles are almost equal to each other as far as these methods are applicable, when the powder is considered to be made of sphere shape particles. However, there are some questions about the particle size measurement of irregular shape particles such as plate or needle like powder. Using mica powders as samples of the thin plate like particles, we compared the results of particle size measurements based on six different principles; optical microscope, sieve, sedimentation balance, photo sedimentation, Coulter counter and Microtrac. The measurement of the particle thickness by the mono-particulate film method gave a relation between the thickness and the projected diameter of mica particles classified by microsieves with a high accuracy. From this relation, the volume of the plate like mica particle was obtained and then the sphere equivalent diameter was calculated. We compared the particle size distribution based on this sphere equivalent diameter with the results measured by the other methods.
†This report was originally printed in J. Soc. Materials Science, Japan, 32(360), 966-970 (1983) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Materials Science, Japan.
Deposition of unipolarly charged aerosol particles flowing through parallel plates has been investigated both theoretically and experimentally. The equation of motion for the particles was solved numerically in consideration of the Coulomb force, image force, particle-inertia force, and fluid-velocity profile. Then the deposition efficiency was calculated based on the limiting trajectories of the particles. It was found that the calculated deposition efficiency, assuming a laminar flow, was a little smaller than the corresponding analytical solution obtained for the plug flow distribution. It was also found that the effect of the image force and particle-inertia force was negligible in the experimental range. The experimental deposition efficiencies for charged fly-ash particles were well explained in so far as the actual velocity distributions were taken into consideration.
†This report was originally printed in J. Soc. Powder Technology, Japan, 20(11), 670-676 (1983) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.
An experimental study of single-particle crushing at slow compression rate was carried out for two kinds of glassy and five kinds of natural materials. The specimens were almost spherical particles of 0.5 to 3.0 cm in diameter. The relationships between particle size and fracture energy (strain energy) were calculated by using the results of the size effect ranging from about 10 cm to 0.0030 cm of single particle crushing, as shown in the previous papers. The experimental results are summarized as follows: 1) The fracture energies obtained were larger than the values calculated from the theoretical equations for limestone, marble and gypsum. 2) For natural materials, the specific fracture energies rapidly increased with decreasing particle size within the range of particle size smaller than about 500 µm.
†This report was originally printed in KAGAKU KOGAKU RONBUNSHU, 10(1), 108-112 (1984) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Chemical Engineers, Japan.
Adaptation of the natural phenomenon of drop formation has resulted in the development of forming seamless capsules. The encapsulation behavior of gelatine in coolant fluid has been studied using a concentric nozzle. The major assumption was that capsules were formed through a wave-like instability in the concentric streams of extruded core, shell, and coolant fluids. Predictions of flow rates and fluid properties were compared with experimental results and were shown to be in reasonably good agreement. It was found that for a given set of flow rates and fluid properties optimum conditions could result in forming uniform size capsules.
†This report was originally printed in J. Soc. Powder Technology, Japan, 20(12), 723-727 (1983) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.
A numerical simulation was attempted for pneumatic conveying of solids in a horizontal pipe. Trajectories of individual particles were calculated using equations of motion. In this simulation, the fluid drag, lift force due to particle rotation and torque on the rotating particles were taken into consideration. The friction loss due to collision of particles with a pipe wall was also calculated using impulsive equations. The pressure drop due to the presence of particles was obtained from the fluid drag acting on the particles through the momentum theorem. To avoid sliding motion of particles on a pipe bottom wall, a model of abnormal bouncing was newly proposed. Several parameters concerning the abnormal bouncing were determined empirically. It was found that the particle flow predicted by the present simulation agreed with measurements regarding particle distribution, pressure drop and particle velocities including angular velocities. In addition, this method was applied to find the effects of particle size, pipe diameter, particle density and so forth. Since particle diffusion due to the air turbulence was neglected in this analysis, the case of fine particles was not investigated.
A simulation of the moving granular-bed type heat exchanger, in which heat is transferred from the hot gas through granular materials and heat pipes to the cold gas, has been performed. A numerical simulation model was made by dividing each part of the heat exchanger into small elements, and heat balance was calculated using the finite difference method. The heat transfer coefficients and effective thermal conductivities of the granular bed in each part of the heat exchanger were estimated from a general theory, while the heat transfer coefficient between the granular bed and heat pipes was determined from the experiment. The steady characteristics of the heat exchanger from the calculations were compared with the data obtained from the experiment. The calculation results coincided well with the experimental results. The method of modeling and simulation was confirmed to be accurately applicable to the estimation of the performance of the heat exchanger using granules as heat transferring media and heat pipes.
†This report was originally printed in J. Soc. Powder Technology, Japan, 20(4), 185-193 (1983) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.