In this paper, the effects of voidage on the rate of mass transfer from the surface of one particle to the fluid in a dilute packed bed are treated.
In order to determine the mass transfer rate for one active sphere in a bed and compare with that obtained for a single sphere in our previous report, the bed consisted of the central active (10 mmφ camphor) sphere and a sufficient number of regular packed (10 mmφ urea resin) spheres that were strung on 1.1 mmφ steel wires. The voidages of the three orthorhombic assemblages investigated are 0.924, 0.821 and 0.718.
In such a high voidage, there exists a laminar boundary-layer flow over a wide range of the Reynolds number, and then the Sherwood number can be expressed as follows: Sh=A+B Re^1/2
which is comparable to the equation for a single sphere. It is reasonable to assume that B, which is determined mainly by a similar transformation variable, η, or by the geometric factor for Uθ (x), contains the voidage parameter (a/b).
Using these values of B for each assemblages and that for a single sphere, the voidage function, f (a/b) , on the particle-to-fluid mass transfer in a packed bed is obtai ned.

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For studying the correlation between filtration and permeation, the newly derived rigorous analytical method which i ncludes the expressions for the flow rate distribution q_z/q₁, through the entire cake and for the true average specific resistance ar was used. The predicted filtration characteristics are compared favorably with actual constant pressure filtration results of dense slurries of various clays.
i) The value of correction factor J, defined by Eq. 13 depends mainly on slurry concentration s but slightly on filtration pressure p. The numerical values of J drop into the neighborhood of 0.9 for dense slurries as shown in Fig. 4. As far as compressible thick slurries are concerned, it has become clear that the conventional theory should be modified.
ii) On both sides of theoretical analysis and experimental studies, it is clear that the average specific resistance of filter-cake should be a function of both p and s. The maximum specific resistance of a cake is supposed to be encountered at the washing stage of the cake.
iii) The ratio of wet cake mass to dry cake mass is also a function of both p and s. The ratio depends mainly on p and slightly on S.
iv) The modern filtration theory is expected to be able to cover various practical aspects of filtration behaviors.

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In this tower, liquid through the nozzle plate set at the top of the tower flows down in rod-like streams for several centimeters, then turns into droplets to continue the fall.
This type has simpler construction and is more convenient for obtaining mass balance than ordinary spray towers.
This paper presents the experimental equations of H_OG, H_G and H_L for this tower. They were obtained respectively from the absorption experiments of NH₃-H₂O, NH₃-H₂SO₄ and CO₂-H₂O systems under various conditions.
Moreover, the relations among these equations have been discussed.

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Experimental investigations were made on how the plate efficiencies of rectification column depend upon the vapor velocities and the reflux ratios, and further the longitudinal distributions of the plate efficiencies were investigated.
In the experiments, a bubble cap column (320rarn dia.) was used, which had seven bubble caps (60mm dia.) per plate and Methanol-Water system used as standard material.
Experimental results show that there are no remarkable differences among the plate efficiencies when the vapor velocities are 20, 30, 40cm/sec, and reflux ratio (total reflux, 2.0R_m, 1.5R_m).
However, the longitudinal distributions of the plate efficiencies were obserbed to become lower near the bottom of the column, and such phenomena can be roughly explained from the slope “m” of the equilibrium curve.

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[in Japanese]

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