The present work was undertaken for the purpose of obtaining a general correlation for the effective interfacial area in packed columns. Studies were made on the absorption of pure carbon dioxide by various solvents in a 7.0cm or 12.5cm column packed with Raschig rings and Berl saddles. The experimental apparatus employed is shown in Fig. 1, and the characteristics of packings used and the run series studied are listed in Tables 1 and 2, respectively.
The values of H_L are shown in Figs. 2 to 5, plotted against liquid rates on logarithmic coordinates. The effective interfacial areas for liquid phase mass transfer were determined from H_L data by using Eq. (1). based on the assumption that the values of k_L in a packed column are approximately equal to those for single piece of packings⁵⁾, when their Reynolds numbers are the same. The fractional effective areas, a_L/a_t, were plotted against liquid rates on logarithmic coordinates, as shown in Figs. 6, 7, 8, 10 and 11. respectively.
The values of a_L/a_t, varied with the liquid rate to the 0.455 power for all packings and systems used.
The effects of the physical properties of liquid were nearly the same on the effective area and on the wetted area²⁾; the viscosity of liquid had no significant effect on a_L, as shown in Figs. 6 and 7, but the surface tension of liquid showed a considerable effect, varying with each packing as shown in Fig. 12.
The present data on the effective area could be correlated by Eqs. (4) and (5) for Raschig rings and Berl saddles, respectively. Figs. 14 and 15 show the comparisons between the values obtained from these equations and the effective areas calculated, by means of Eqs. (1) or (2), from the previous data on liquid phase mass transfer rates in packed columns. Considerably good agreement is observed between the values obtained from the authors' equations and the previous data.

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An experiments on the absorption of pure carbon dioxide by water containing a wetting agent (Emerl), was conducted in a 7.0cm dia. column packed with 15mm Raschig rings.
The results obtained are shown in Fig. 1, as a plot of k_La vs. L on a logarithmic scale. The effect of wetting agent on the absorption rates can be observed in this figure and more clearly in Fig. 2, where k_La at a constant value of L (15, 000kg/m²·hr) is plotted against the concentration of the againt. With the increase in the concentration, k_La decreases until it reaches the minimum at a certain concentration, and then it begins to increase. These results are similar to those obtained by Rennolds⁷⁾ on the desorption of carbon dioxide, which was carried out using 1/2in. carbon Raschig rings as packings.
Variation of k_La with the change in the concentration of the agents may perhaps be due to the fact that the two effects are contradictory to each other. With the increase in the concentration of the agent. liquid phase mass transfer coefficient, k_L, decreases, but the effective interfacial area, a, increases, -the former probably because of the incomplete mixing of liquid at the juncture points of packing pieces, ⁶⁾ and the latter because of the decrease in surface tension.⁴⁾
Based on this idea, the effect of surface tension on the effective interfacial area has been determined for the case where 15mm Raschig rings are used. which shows good agreement with the results reported in the previous paper.⁴⁾

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Electric analogue circuits are used for evaluating the effective thermal conductivities in packed beds without fluid flow, taking into consideration the numbers of packings placed in the direction of heat flow.
In the analysis, it is assumed that the thermal resistance within packed beds may occur in the following forms:
(1) Thermal resistance of packing itself.
(2) Thermal resistance of contact area.
(3) Thermal resistance of fluid between packings.
(4) Thermal resistance to heat radiation from packing to packing.
(5) Thermal resistance to heat radiation from packing to adjoining packing beyond one.
The equations obtained are given in the form of Eqs. 1, 3, 6 and 7. Introducing the values of thermal resistance into Eq. 7, we have obtained Eq, 8 which expresses the relation of k_s/k_g.
Experiments have been carried out with various packings: iron, porcelain, glass balls and insulating fire bricks at the temperature between 100 and 1000°C.
Comparisons between the experimental results and the values obtained from Eq. 8 are shown in Figs. 11, 12, 13, 14 and 15. The calculation can be readily handled by employing the chart of Fig. 8, without using the complicated formula, Eq. 8. The difference between the value obtained from the chart (Fig. 8) and that obtained from Eq. 8 is small and negligible.

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Several studies ever conducted on the pressure losses of a venturi scrubber were scarcely subjected to theoretical analysis and the results were merely expressed by the following empirical equation.
(1)
In order to give some theoretical considerations to the above equation, we studied, in the first place, only the pressure drop through the venturi pipes as shown in Fig. 2, where no liquid was injected.
The starting point for our calculation of pressure and velocity was located on the venturi axis in Section 3, where the difference of statical pressure between the center and the wall side was found to be minimum as illustrated in Fig. 4. Then the pressure dropes in Sections 1 and 4 were calculated. Theoretical pressures without any losses were obtained for Section 1 and 4 by means of E_qs. (5) and (15), respectively, paying due attention to isothermal change in compressible fluid. Next. the pressure losses were evaluated by dividing them into three parts, -the pressure loss in the convergent part of the venturi tube, in the throat part and in the divergent part thereof-and by incorporating them in the end.
In the convergent part, the pressure change (Δp_1-2) was found to be the sum of (i) the pressure drop due to velocity increase and (ii) the loss of friction, as indicated by E_q. (13). In the throat part, the pressure drop (Δp_2-3) was caused only by the friction loss, as expressed by E_q. (14). From the above considcration, the difference in pressure between Section 1 and 3, that is Δp_1-3, which was calculated from Δp_1-3=Δp_1-2+Δp_2-3l, may be regarded as the best representation of the experimental values, as shown in Fig. 5. In the divergent part, the pressure change (Δp_3-4) was obtained from E_q. (16), but it is apparent from Fig. 5 that the values ( ) calculated by means of E_q. (16) did not show very good agreement with the experimental values ( ), when the throat velocity was higher. These values were obtained from E_q. (16) into which was introduced Gibson's empirical E_q. (17) in the place of Δp_3-4l, which indicates the loss due to the increase in the cross section.
On the other hand, good agreement is observed between the calculated values (dotted line) and experimental data ( ) as shown in Fig. 5, when Δp_3-4 was calculated by using E_q. (18) in which ζ was evaluated by means of E_q. (20) whose β is illustrated in Fig. 6 and Eq. (21) as a function of
The typical example of the total pressure drop through the venturi tube calculaed by E_q. (23), which was obtained by adding E_qs. (12), (14) and (18), is given by a solid line in Fig. 7, where the corresponding experimental data are marked by . When ρ₁≅ρ₃≅ρ₄ and m² is neglected, Eq. (23) is transformed into Eq. (24). Values for the aforesaid example obtained from this epuation are marked by a series of in Fig. 7.
Thus we may conclude that the value, equivalent to b in E_q. (1), can be given as follows, though merely for a practical purpose: and that b may be considered a function of the shape of a venturi tube and also a function of the properties of fruid passing through the throat.

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The results obtained of our experiments conducted on water jet scrubbers may be summarized as follows:
1) Pressure drops in a water jet scrubber can be represented by the empirical E_q. (1) and collection efficiencies by E_q. (3). Swirl-type liquid jet nozzles show better collection efficiency than straight flow nozzles, but the pressure drop in the former is fairly larger than in the latter. (about 3 times)
2) Pressure drops in venturi scrubbers with any venturi throats can be obtained from E_qs. (4) and (5).
3) If inlet dust concentrations become heavy, the collection efficiencies tend to increase.

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