A theoretical formula for effective thermal conductivities of packed beds, was obtained, by using a simple model consisting of thre components of different thermal conductivities arranged in paralle1, i. c.:
1. A component consisting of packings and interstitial medium
2. A component consisting of packings which, when packed, form contact-conducting paths, and
3. A component consisting of interstitial medium filling the void through which heat is conducted.
In the meantime, the electric conductivities were measured of the beds filled with conductive fluid so as to be compared with the above thermal conductivities, and the results were summarized in a formula analogous to that for effective thermal conductivities.
λ₈, λ_f, λ₈: thermal conductivity of bed, interstitial mcdium and packing, respectively [kca1/mhr°C]
c=1-ε^1.3
d: constant varying with void and (λ_f/λ₆), Fig.11
ε: void
d_p: diameter of packing [m]
h_r: heat transfer cocfficient by radiation [kca1/m²hr°C]

View full abstract

It has been recognized that the caked cloth presents resistance to filtration different from that of the clean cloth, but the numerical relations between these two resistances have not been explafined yet.
In the study of the problem, the author has found the constancy of the value of b_fv/r_fv, and this means that the resistance coefficient of the caked cloth, b_fv, is proportional to the specific resislance of the cake, r_fv, even if the cake is compressible. The numerical relation between the value of b_fv/r_fv and the woven dimension of the cloth has been made clear by this explanation.
The value of b_fv/r_fv and the microscopic study of the caked cloth may be a good guide for the selection of a suitable cloth. In the case of a suitable cloth, the value of b_fv/r_fv is less than lmm, as shown in Table 2 and 3.

View full abstract

Layers of powdery and granular materials were dried in an infrared dryer shown in Fig.1, under various conditions as follows and the experimental results weres summarized as in Table 1.
Kinds of Materials Used
River San
Standard Sand
Iron Particle
Wood Powder
Porcelain Clay
Experimental Conditions
Diameter of Layer
Thickness of Layer
Air Temperature
Air Velocity
Intensity of Infrared Projected
Average Diameter(mm)
0.74, 0.27, 0.14
0.13, 0.088, 0.073, 0.041, 0.022, 0.009
0.74, 0.54
0.16
Under 0.043
15cm
7-61mm
5-35°C
1.14-1.34m/sec
4, 400-9.000kcal/m2h
The temperature distribution in the direction of depth, measured with a device shown in Fig. 2, was found to be important in the study relative to the conditions employed by the authors, as it had close relation with the characteristics of the falling rate drying, as shown in Figs.3, 4, 8 and 9.
From the above results, it was concluded that the thermal conduction through the dried-up layer, located between the surface and the wet sublayer, would play an important part in the drying of said materials in the second falling rate period.

View full abstract

Analysing the experimental data presented in their previous paper⁷⁾, the authors have found that the boundary zone between the dried-up layer and the wet sublayer proceeds gradually downward to the bottom.
In the case of a layer of coarse granular solid, whose diameter is larger than O.27mm, the local water content of the layer is assumed to be constant under the authors' experimental conditions in the falling rate period. The theoretical equations, Eqs. (8) and (14), have been obtained using amodel of heat transfer as shown in Fig.2.
Comparison of the theoretical values with the experimental data in Figs.3, 4 and 5, may prove the adequacy of Eqs. (8) and (14) for the coarse granular solid layers.
Relative to the layers of fine particles, the experimental data have been analysed by means of the fundamental equation, Eq. (15), and Figs.6, 7 and 8 are obtained, which will confirm the assumption, that the boundary zone gradually moves as the total percentage of saturation decreases.

View full abstract

A method for calculating the number of transfer units, when the amount of transfer between the phases are not small, have been studied.
Pertaining to the solute mol-ratio to the inert material, the operating line always becomes straight, and the number of transfer units can be calculated by Eq. (9). When the logarithmic mean is assumed to be equal to the arithmetic mean, Eq. (9) is simplified to Eq. (10), which, again, may be rewritten as Eq. (11), when the equilibrium line is assumed to be a straight line, Y*=mX+b, But when the equilibrium 1ine is curved, the number of transfer units may be calc ulated by means of Eq. (13), according to White's method.
As shown in the examples, this method of ours gives better approximation than any of the previous ones, and the error in this case is less than 1% of the results of graphical integration.

View full abstract