The excess thermodynamic properties of associated solutions are discussed by using the linear association models (I) and (II). The linear association model (I) deals with the self-associated system by making distinctions between the association constant and association energy of dimer formation and those of polymer formations. The results of the calculation show that the distinguishing effects are relatively small in quality. The linear association model (II) is proposed as one of the models for the system having the species associated with like and unlike molecules. A characteristic of this model is the existence of a maximum point on the activity coefficient curve. Good results are obtained in the application of model (II) to correlate and interpret the vapor-liquid equilibria for binary mixtures of alcohols and interacting solvents.

View full abstract

The BWR equation was applied to correlate the vapor-liquid equilibria of the polar-nonpolar systems. Polar components studied were Freon-22, hydrogen sulfide and ammonia. The vapor-liquid equilibrium data were cited from the literature, except for the Freon-22 mixtures whose data were obtained by a static method in this paper. The BWR constants also were taken from the literature, but those of Freon-22 were determined from the principle of corresponding states and of ammonia from the P-V-T data.
By introducing the interaction parameter into the constant, A₀, the BWR equation was shown to be successful for correlating the vapor-liquid equilibria of the polar-nonpolar systems. The characteristics of the parameter were discussed based on the concept of intermolecular potential between unlike molecules.

View full abstract

The prediction accuracy of the Wilson, NRTL, and Heil equations is shown on a wide variety of multicomponent completely miscible systems including two quinary, seven quaternary, sixty-nine ternary systems. Vapor phase nonideality was taken into consi- deration in all numerical calculations. This assumption improves generally the accuracy in the vapor composition and total pressure calculations for multicomponent systems which were obtained under the assumption of an ideal vapor phase. The Wilson equation seems to be the best of all the equations.

View full abstract

In order to investigate the effects of hydrogen-bonding on thermodynamic excess properties in alcohol-nonpolar liquid solutions, the self-associations of ethanol in carbon tetrachloride, n-hexane and cyclohexane, and of methanol in carbon tetrachloride at 15°, 25°, and 35°C are studied by infrared spectroscopy. The spectroscopic data obtained for these systems can be interpreted by the monomer-cyclic tetramer model of alcohol, and also by the continuous chain association model of alcohol, under the assumption of athermal associated mixtures. The association constants and association energies of these alcohols are determined on the basis of these models.
By the comparisons of the excess free energy, G^E, and activity coefficient, γ_i between the experimental values and the ones calculated by these two models, it is shown that the continuous chain association model gives better agreement than the cyclic tetramer model does.

View full abstract

In order to clarify the hydrodynamic performance of the gas-liquid mixture above a gas distributor, the gas void fraction and the froth height for the foam layer with a low clear liquid height on a perforated plate under liquid stagnant flow were studied theoretically.
In the present work, it was assumed that the shape of a bubble in the foam layer was a spherical capped bubble. Further, it was considered that the bubble rising through the liquid was accompanied by some volume of liquid as the wake behind it.
As a result, it was found that the gas void fraction and the froth height are given by a function of the Froude number based on the clear liquid height and the liquid hold-up. Furthermore, these equations were compared with the results obtained by Azbel and Kim.

View full abstract

The fluid dynamics of recirculation flow induced by a jet stream was investigated theoretically in a two-dimensional channel, deriving both the recirculation flow rate and turbulence intensities generated by the jet stream, these being the main factors for mixing of fluid.
In the authors'' measurements previously reported, it was shown that the turbulence was highly anisotropic in the recirculation zone. Therefore, an advanced theory was proposed in this paper, in which high anisotropy of turbulence in the recirculation zone has been considered. Then, it became possible to derive the recirculation flow rate and turbulence intensities theoretically in the whole recirculation zone. The present theoretical results could explain fairly well the tendency of recirculation flow rate and turbulence intensities correlated with the similitude parameter (Curtet number).

View full abstract

The difference between the effective diffusivity of a cylindrical porous catalyst under reacting conditions, D_e^R, and non-reacting conditions, D_e^D, was studied experimentally and theoretically (on the basis of the pore model).
It was concluded that the "local value"^** of D_e^R substantially agrees with that of D_e^D. But the "apparent value" of D_e^R obtained experimentally was greatly affected by the non-uniformity of the catalyst pellet, that is, the local value of D_e^D was non-uniform. Especially when the reaction was carried out in the intraparticle diffusion limited region, D_e^R apparently became much smaller than D_e^D.

View full abstract

It is pointed out that both the sonic velocity limit at the top (SVL) and the top pressure limit (TPL) should be considered as upper limits of vapor flow rate in a falling film column under vacuum distillation. These limits are represented in dimensionless forms and graphically, based on pressure drop equations involving a compressibility effect. Discussions are made also on the vapor Reynolds numbers corresponding to flooding and to the minimum wetting rate of reflux, and the effective operating range is illustrated.

View full abstract

An unique perturbation method for the distillation calculation of a non-ideal system was proposed by Acrivos and Amundson. This method, however, is limited only to the first-order perturbation and gives an approximate solution, for the equation with the second and further perturbed terms is too complicated to use for practical purposes. To improve this point the Double Perturbation Method is presented here. Although the equations used in the presented method are obtained by the same reasoning as the above authors, this method, whose tiresome procedures can be overcome by computer, gives the strict solution.

View full abstract

Although the well-known assumptions, constant molar rate and random mixing of liquid on the tray, are used, plate efficiencies incorporating the thermal effects have been applied to distillation calculations by matrix, successive iteration and plate-top-plate methods.
Using the numerical example of a ternary system, it has been demonstrated that the distillation calculation using the plate efficeincy has great influence on the determination of the composition profile as well as the designation of the distillation column. For a quaternary distillation system, the convergence process by means of matrix and successive iteration methods has been illustrated.

View full abstract

A new calculation method is proposed for a non-ideal multicomponent distillation column with one feed. The Successive Iteration Method proposed by Sugie and Yamada was modified basing on the principles of perturbation. The over-correction of the relative volatility in an iterative process is improved by introducing a parameter n whose value determines the magnitude of the correction. The six examples considered by Hirose and Hiraiwa and two additional examples were considered in this investigation for testing the applicability of the proposed method. A comparison with the methods available in the literature indicates that the proposed method gives excellent convergence.

View full abstract

A study was carried out to establish a method for easy estimation of bubble size distributions as a function of height in gas fluidized beds.
Assuming a simple model of bubble coalescence, equations were developed for the calculation of bubble size in two- and three-dimensional beds. From those equations the bubble size at any height can readily be calculated through the initial size which is given from only the operating conditions and the characteristics of the fluidized particles. The equations were examined by comparing the calculated values with those observed by the authors and many other workers for various kinds of particles. It is shown that the equations can approximately interpret the experimental data over a wide range of operating conditions.

View full abstract

Air pressure was applied to initiate flow of cohesive powder from a blocked hopper. The effect of air pressure was examined by describing the distributions of air pressure and solids pressure within a hopper and by assuming a simplified block-flow model.
As a result, it was found that air pressure applied from above the powder bed was more effective than that applied from below the hopper outlet. Further, the flow criterion under gravity alone was also evaluated on the basis of the same proposed model. Air pressure was found to be useful in practice, judging from the relatively low pressure required and its easy operation.

View full abstract

Maxwell''s equation was applied to a current line between electrodes to measure the mean concentration by the electric conductivity method. It is concluded that this method may cause fatal error of measurement in a field of fluctuating concentration if the relative concentration differences are large.
The discrepancies between measured and mean concentrations were evaluated for the complete segregated model and Gaussian distribution models of concentration with a flowrate ratio of 1 :1 to 1 :9. The use of pure water to measure mean concentration in the mixing process must be avoided.
The lower/upper concentration ratio is recommended to be around 0.5 for all flow rates ratios in order to measure the meanconcentration within errors of 5% even in the most extreme cases.

View full abstract

In order to study flooding velocities, various types of plate column without downcomer (sieve trays, sieve trays with holes of two different diameters, turbo-grid trays, ripple trays and rotational-current trays) were used.
The flooding velocities of these trays were well correlated by modifing the correlation of flooding velocities in packed columns which was proposed by Zenz and Eckert.

View full abstract

The effects of operating temperature on the characteristics of fluidized beds were investigated. It was found that the minimum fluidizing velocity, the bubble frequency, and the apparent bed viscosity, were affected considerably by the rise of temperature.

View full abstract

A theoretical analysis of a continuous-renewal type air filter is discussed in succession to that of a partial-renewal one, which was dealt with in our previous paper. Various computations are carried out, using the mathematical model (partial differential equations), which is derived in the same manner as those in the latter paper. Consequently it is concluded that a continuous-renewal type air filter is superior to a partial-renewal one from the economic standpoint of medium consumption and the appropriate renewal velocity can be estimated easily, etc.

View full abstract