In our previous paper, the holdup and the mixing characteristics of liquid flowing through the irrigated packed towers (I.D., 4-7cm) had been determined. An attempt was made, in this paper, to extend the range of experimental variables, in order to larify the influences of packing size and type as well as the ratio of packing diameter to tower, either on the holdup or on the mixing characteristics of the liquid in packed beds.
For this purpose, the transient response curves were measured, by using larger packed beds, whose properties are listed in Table 1. From these response curves, the holdup and the mixing coefficients of liquid were determined by the graphical integration of the curves, based on Eq.(5) and by the method described in our previous paper, respectively.
The experimental results of this study and of the other sutdies previously reported and summarized in Figs. 2, 3 and 4, show that the packing type and the ratio of the packing diameter to the tower diameter have little influence either on the holdup or on the mixing coefficients of the liquid in packed beds. Therefore, the generalized correlations have been obtained as follows:
Eqs.(8) and (9) for the operating holdup of the liquid in irrigated packed beds.
Eqs.(11) for the mixing coefficients of the liquid in irrigated packed beds.
Eq.(10) for the mixing coefficients of the liquid in liquid-packed beds.

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Experimental studies were performed on the perforated-plate extraction column with reciprocated flow, utilizing the characteristics at lower operating limit of the pulsed plate column.
By employing the method of pulsation as shown in Fig. 1, the efficiency of extraction was raised to the higher level because the liquid-mixing occurring across the plates was obstructed, and the capacity coefficient was expressed by a simple formula due to the simplicity of the operating conditions.
The capacity coefficient increased with the decrease in diameter of the perforations, but the distance between the centers of the perforations had to be larger than the frontal diameter of the ellipsoidal drops. If not, the capacity coefficient would become lower, since the rising drops would combine with each other and the effective surface for the extraction would decrease.
The holdup of the dispersed phase was observed to consist of two parts:-static holdup and operating holdup. The static holdup was of such a quantity as would be indispensable for the ispersed phase to drench the surface of the plate and spout uniformly through the plate, and the operating holdup was decided by the relation between the periodic time of the pulsation and the time needed for the dispersed drop to spout through the plate and combine with the upper organic solvent layer.

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Natural convection induced by heating a part of a vertical ylinder of finite length was investigated.
The heat transfer to a laminar fluid flow inside cylinders has already been studied by many authors since Gratz. Recently, Sellars and his coworkers analyzed this problem by the use of W-K-B approximation, and Whiteman and Drake extended the application of this method to a flow with a profile expressed by u₀ (1-γ+^m). However, the W-K-B method does not give a good approximation to problems where the eigenvalues are not large and several incipient terms are dominant for the solution. Moreover, most of the authors have assumed a constant value for the density of the fluid. This will cause a big error when we deal with a flow caused only by natural convection.
In this report, three fundamental equations for fluid flow were analyzed for a system represented by Fig. 1. Temperature dependence of the density of air was taken into account by employing the relation given by Eq.(4). From the energy equation (3), combined with the continuity equation (1) and the boundary conditions of the system, the temperature distribution functions in the cylinder were obtained as given by Eqs.(14), (15) and (16). These distribution functions were applied to the momentum equation (2), and integrated for one complete cycle of the convection, as given by Eq.(18). The result is given by Eq.(19), (where the abbreviations of Eqs. from (20) to (25) are employed) by which the rate of convection, or the Reynolds number Re⁰ can be estimated as a function of T_w-T₀ andthe geometrical structure of the system.
The W-K-B approximation and the estimation by a digital computer were applied to the solution. Values of several incipient terms of eigenvalues λ_n and coefficients C_n are given in Table 1, and are compared with the values obtained by Abramowitz, who tried to give accurate values by expanding the differential equation by Bessel function. Only those results estimated for m=2 were tabulated, though other values of m were examined, too. The values obtained by the computer show good coincidence with those by Abramowitz. The former may be more reliable than the latter. The W-K-B method gave poor result
In Figs. 3, 4 and 5, the areal mean rate of convection is shown as a function of wall temperature. Good coincidence is mostly found between experimental and computed values. In Figs. 4, experimental values for large T_w-T0 T_o are somewhat higher than estimated values. In this region, the Reynolds number exceeds 1, 500 and the parabolic flow assumption might be inapplicable. On the other hand, in Figs. 3 and 5, the observed rates are lower than those estimated for large values of T_w-T₀. This might be attributed to a dominant effect of the use of ρ₀ and β₀ instead of ρ and β in the estimation of the rates by means of Eq.(19).
In Figs. 6 and 7, the effect of the location of the heating section on the wall temperature is shown, by taking the areal mean velocity u_o as a parameter. It will be seen that the height of the heating section has a predominant effect on the rate of convection. Radius of cylinder also produces a large effect on the rate of convection. When the radius is small, the viscosity of the gas retards the flow rate, and when it is large, prolonged heat transfer retards the rate, too. There must exist an optimum radius for an assigned rate of convection. Fig. 8 shows this situation. The chain line in the figure shows the optimum radius for obtaining the highest rate of convection by a given temperature and a given height of the heating section.

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