Tsutomu Aragaki

Dynamic characteristics of a multistage thermal diffusion type solar distillator

Abstract Dynamic characteristics of a multi-stage solar distillator were studied by formulating the rate equations and the heat and mass balance equations with respect to the process variables. The results obtained by the simulation showed satisfactory agreement with the data taken from both a laboratory test plant having 5 stages with 1 m 2 and a field test plant having 10 stages with 3 m 2 in frame area. The operation conditions required to maximize the distillate productivity were predicted on four sample days through a year. Then sensitivities of the distillate productivity were estimated. Availability of using concrete slab instead of the solar energy recieving plate was also substantiated.

Analysis of packed distillation columns with a rate-based model

Multicomponent packed column distillation is simulated using a rate-based model and the simulation results are compared with the experimental results obtained from a 0.2 m diameter pilot-scale packed column. The simulation algorithm used is previously proposed by the authors, which based on an equation-tearing method for (6c+7) equations of one packing segment and the whole column is solved by an iterative segmentwise calculation with the overall normalized θ method for acceleration. The performance of two packings is examined by simulating the pilot-scale column experiments using the published correlations for estimating liquid and vapor phase mass transfer coefficients and an effective interfacial area.

Hold up and flow of liquid film at a horizontal tube bundle

Abstract Hydrodynamic aspect of liquid flow at a horizontal tube bundle was studied to provide basic idea in promoting the performance of thermal desalination processes. The hold up is almost saturated at the flow rate over 300 ml per one meter of pipe length. The effect of wound thread was observed by changing the pitch and diameter, and discussed the condition to minimize hold up from a view of heat transfer enchancement. The shape and size of a liquid droplet hunging beneath a horizontal pipe is also calculated by the finite element method, and the result are compare with the experimental observations.

Shape coefficient of a non-spherical particle to characterize heat transfer

The shape coefficient of a non-spherical particle to characterize heat transfer was defined by using the similarity of the transient cooling curve of a sphere. Namely, the reducing radius of the sphere could be determined to minimize the error of curve-fitting. The ratio of the reducing radius to a representative radius of a non-spherical particle was then defined as the shape coefficient. The shape coefficient was calculated for cylinders, rectangular solids, and elliptical bodies as typical non-spherical shapes, and nomographs are presented for aspect ratios from 0.1 to 10 and Biot Numbers 0-100. The nomographs are bell-shaped curves with respect to the aspect ratio, having a peak near unity and monotonously decreasing to about 50% of the shape coefficient at the peak. When the aspect ratio is changed from 1.0 to 2.0, for example, the change of the shape coefficient is only in the order of 5%. Even over a wide range of Biot Numbers, the shape coefficient differs at most by 10%. This feature permits the shape coefficient of almost all particles to be approximated by one of these three typical non-spherical shapes.