The Venturi scrubber is being used successfully for the removal of micron and submicron particle matter, both in solid and liquid state, from gas streams. The collection is thought to be mainly done at the throat by the deposition of particles on water droplets by impaction, and the separation number of the particle determines the deposition efficiency. This paper treats the theoretical study of the collection efficiency at the Venturi diffuser by the same way as the 1st report. Some results of calculations are illustrated, and they indicate that the diffuser makes no small contribution to the collection.

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A simple method for calculating the laminar boundary-layer has been obtained. The method consists in using the approximate formula for the energy thickness and the diagram which gives the relation between σ^*, ω^* and T^*, where σ^*=θ^*2U'/ν, ω^*=σ^*2(UU"/U'²), T^*(τ₀/ρ)×(θ^*/νU). The notations are as follows : θ^*=energy thickness, χ=arc length of the surface of the body, U(χ)=velocitv just outside the boundary-layer, τ₀=shearing stress on the surface of the body, ρ=density of the fluid, ν=kinematic coefficient of viscosity. When U(χ) is given, θ^* is calculated by an approximate formula and the relation between σ^* and ω^* is determined. Then by using the diagram, the values of T^* are found, which giveτ₀ for each point on the surface of the body. Some results obtained by this method coincide satisfactorily with the exact solutions and the results of experiments. As the necessary calculations are simple, this method is useful for the engineering purpose.

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Fundamentally, the properties of rarefied gases must be deduced from Maxwell-Boltzmann equation. We will treat the problem of steady one-dimensional heat transfer between two plates in the rarefied gases. H. Grad expressed the distribution function of the gas molecules in the Hermite polynomials. This method, however, cannot satisfy the boundary conditions that the distribution function is discontinuous between incidental molecules and reflecting ones. Then we will devide the distribution function for incidental molecules and for reflecting ones separately, which have different coefficients. Using this distribution functions, we get four equations of the moments of distribution function and three equations can be obtained from the Maxwell-Boltzmann equation. From these seven equations we can solve the temperature distribution between two plates in the rarefied gases as the function of the distance from the wall. And we get the relation between wall temperature and heat flux vector.

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In the previous paper, we solved the problem of the heat transfer between two plates in the rarefied gas. The equation obtained in that case contains some constants such as A^±, L^± and B^±. We executed the experiment about the heat transfer between two plates and from those results determined the constants. The experiment consists of the measurement of the coefficient of heat transfer using the transient phenomena. To determine the constants, we simplified the original equation under some assumptions.

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An air chamber is set up at either the first or the second throttle of an air-micrometer. The air chamber is partitioned from wall to wall with a corrugated diaphragm, in the centre of which a small aperture is bored to serve as inlet or outlet throttle depending on the direction of air flow. Then the characteristics of such an air-micrometer will represent the combination of the characteristics of an ordinary air-micrometer and the deflecting characteristics of the diaphragm. If a large magnification is provided for the air-micrometer, the spatial change of the concerned throttle in relation to the deflection of diaphragm will be little affected, that is, the non-linearity of the characteristic of the air-micrometer may be ignored. As a result, under such positive or low negative pressure, as usually renders the characteristic of a conventional air-micrometer non-linear, there will be a linear characteristic over the wide range of measurement. Provisionally designating such apparatus as Diaphragm Type Air-Micrometer, the authors analyse in this paper the low vacum range, which is most easy to work. The characteristics of an air-micrometer using a capillary tube for the second throttle to attain large magnification and those of the diaphragm, have been separately sought and then they were combined to derive characteristic formulas. General coincidence of those formulas with experimental result was obtained.

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Most of the nozzles used in pneumatic spreader stoker diverge horizontally and converge vertically in order to spread the fuel particles uniformly on a fire grate. This paper deals with the dependence of the diverging ratio and the form of nozz1e, which closely affect the spread states of fuel particles on a fire grate, upon the friction losses in the nozzle. The diverging ratio is defined as the ratio of cross section at the entrance of nozzle and that at the exit of nozzle. The following results were obtained. Optimum diverging ratio of nozzle is somewhere around 1.0, and optimum form is as follows; -1.5×10^-2>Ψ>-3×10^-2 where Ψ=tan θ×tan ψ 2θ=diverging angle of nozzle in horizontal plane. 2ψ=diverging angle of nozzle in vertical plane, As long as the nozzle is not clogged with particles, the larger the ratio of the weight of particles to that of the air is, the less the losses in nozzle are.

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