Shrinkage of sodium polyacrylate gel in an electric field was studied from the viewpoint of the ion exchange between sodium ions dissociated from –COONa groups in the original gel and hydrogen ions generated by the electrolysis of water. This mechanism was confirmed qualitatively by the following facts, obtained in a study of spherical gel particles of vinyl alcohol/sodium acrylate copolymer. 1) Remarkable shrinkage is observed at voltages above the electrolysis voltage of water. 2) The shrinkage proceeds near the anode, where hydrogen ions are generated. 3) The amount of sodium ions released from the gel particles by exchange with hydrogen ions increases with increasing amount of electricity. 4) The degree of shrinkage of gel particles also increases with increasing amount of electricity. 5) The rate of shrinkage increases with increasing electric current as well.
Donnan dialysis concentration of cupric ions was examined experimentally, using four commercial membranes and synthetic membranes prepared by the paste method. The enrichment rate and its ratio in Donnan dialysis were affected by membrane properties. From experimental results using commercial membranes, a large value of (ion-exchange capacity)(self-diffusion coefficient of cupric ion)/(membrane thickness) was found to be a criterion of high ionic flux through a membrane. Diffusion coefficient, ion-exchange capacity and water content of a synthetic membrane were affected mainly by the degree of crosslinking of the membrane. A synthetic membrane with a degree of crosslinking of 0.02 and reinforced by polyvinyl chloride cloth showed higher ionic flux and lower flux of osmotic water, and gave a higher enrichment ratio than those of the commercial membranes used in this work.
Distillation with internal heat integration, in which energy is recovered by heat transfer from the rectifying section to the stripping section, is an effective method for energy saving in distillation columns. This paper analyzes the effects of distillation parameters such as relative volatility, column height and product specification on the energy reducibility of a packed distillation column with internal heat integration. To make the effectiveness of internal heat integration clearer, the stripping section, the rectifying section and the integrated column (consisting of both sections) were analyzed separately. It was found that: 1) energy saving due to internal heat integration of the stripping section is more sensitive than that of the rectifying section; 2) especially for the stripping section, the reduction of the heat duty at the reboiler is greater than the quantity of heat added to the side of the column, provided that the column is short enough; and 3) for the integrated column, the effectiveness of the internal heat integration is comparatively greater when the relative volatility is large and the specification of the product purity is loose.
The minimum seed crystal size or the minimum size, usually defined as the critical size greater than which seed crystals can produce secondary nuclei, was measured for potassium alum secondary nucleation using a seeded stirred-vessel crystallizer. The value was lowered with increasing stirrer speed both for stainless steel and acrylic resin impellers. The former impeller gave a smaller minimum size than the latter. The minimum size was newly interpreted as a measure of difficulty of nucleation, by defining it as the seed size at which the nucleation rate, being increased as the seed crystals grow, reached a certain detectable level. The behavior of the experimental results and literature data (effects of stirrer speed, supersaturation, impeller materials, impurities and system size) for laboratory crystallizers were reasonably but qualitatively explained in terms of secondary nucleation caused by crystal-impeller collisions. It was concluded that nucleation data obtained in a laboratory, using a small crystallizer, would be difficult to apply to industrial crystallizers because crystal-impeller collisions are unlikely to occur in large-scale industrial systems.
The occurrence and structure of longitudinal vortices are examined by a flow visualization technique for various sinusoidal wavy channels. Longitudinal vortices are confirmed to appear in a channel with a narrow spacing in the range of geometrical parameters considered here. The geometrical conditions for the onset of such vortices are shown by a diagram. The longitudinal vortex is a kind of Taylor–Goertler vortex observed in a curved rectangular-section channel. However, the wavy channel is different from the curved rectangular-section channel in the processes of vortex development and destruction. It is found that an unstable mode, in which the vortices formed at the upper and lower walls of the channel have some interaction, leads to vortex destruction and significantly promotes the transition to turbulence.
For an inclined plunging jet aeration system using liquids of low viscosity, the effects of operating conditions on the gas entrainment rate Qg when nozzles having various values of length-to-diameter ratio Ln/Dn were employed were evaluated experimentally. The changes in Qg were related to those in the jet shape before plunging and the liquid velocity distribution at the point where the gas sheath breaks up. An empirical equation was presented to predict the penetration depth Z of bubbles entrained by the diffusing jet. Bubble entrainment behavior was further examined in terms of the liquid velocity distribution in the submerged two-phase region and the size of entrained bubbles.
The flashing temperature of superheated water droplets dispersed in fuels was measured to investigate the micro-explosion of emulsified fuels. As fuels, kerosene, diesel fuel and tetradecane were used. Water, aqueous methanol and ethanol solutions were used as the dispersed phase. The emulsions were prepared by two methods: mechanical and ultrasonic, and were stabilized by Span 80. The emulsion samples in a test tube were heated in an oil bath at a rate 2 K/min. The flashing temperature, represented by the 50% flashing temperature, decreases with increasing surface area per unit volume of the emulsion sample. The flashing temperatures were observed to depend on the composition of both the continuous and dispersed phases; this dependence was expressed as a function of the surface excess of surfactant.
An improved voltage jump method characterized by a higher time resolution (0.2 μsec) as well as a larger dynamic range (80 dB) than the conventional method is developed to measure electric current relaxation accurately. by this method the rate constants in the valinomycin-mediated transport of potassium ions through an azolectin bilayer membrane are determined from the current relaxation curve. From an investigation of the influence of applied voltage and temperature on each rate constant, a potential energy profile and a displacement of the potential energy profile depending on applied voltage are estimated.
This paper describes an experimental study of flow characteristics of isothermal axisymmetric suddenly expanding swirling flow with bluff body using a backward-scatter two-component laser-Doppler velocimeter. Axial and tangential velocity components including time-mean and rms fluctuating values are determined. Some quantitative information, such as the boundary and strength of the reverse-flow zone, are provided.
Cation exchange membranes were prepared using styrene and divinylbenzene as respective components and polyvinyl chloride cloth and microporous polyethylene film as respective backing materials. The intramembrane structures of synthetic and commercial membranes were analyzed using Tye’s treatment by considering the non-homogeneous charge distribution within the membrane. Volume fractions of the pore, polyelectrolyte and inert polymer phases within the membrane were determined by using the water content of the membrane and the Donnan sorption concentration. The diffusion coefficients of the cupric ion within the pore and resin (i.e., polyelectrolyte and inert polymer) phases were correlated with the respective volume fractions of the membrane. A simplified model of the intramembrane structure was found to be useful for evaluating the sorbed concentration and the membrane conductivity.
The extraction equilibrium of organic acids (acetic, glycolic, propionic, lactic, pyruvic, butyric, succinic, fumaric, maleic, malic, itaconic, tartaric, citric and isocitric) with tri-n-octylphosphine oxide (TOPO) was measured. The solvation numbers of the acids were the same as the numbers of the carboxyl groups on each acid molecule. The extraction equilibrium constant was controlled by the hydrophobicity of the acid when hexane was used as a diluent.
To evaluate their usability as adsorbents in chemical heat pumps for high-temperature use (over 373 K), an accelerated aging test by steam was performed for various zeolites and the adsorption equilibria of selected zeolites were measured. from the high-temperature steaming test it was found that high-silica zeolites like Na-mordenite, USY (ultrastable Y) and HY had higher thermal stability than conventional A- or X-type zeolite. Further, measurements of isotherms of Na-mordenite and USY showed that they maintained adsorption capacity even at 473 K. Acquired isosters of each zeolite and water were approximated as straight lines in the range from room temperature to 473 K. On their charts, heat transformer (chemical heat pump) cycles that work at high temperatures could be generated. High-silica zeolites like Na-mordenite or USY are therefore expected to be usable as adsorbents of water for repeating chemical heat pump operations at high temperature, though their total adsorption capacities are smaller than those of A- or X-type zeolites.
Commercial acrylonitrile fibers of 1.2, 1.5, 3, 8 and 15 denier were separately treated in a 0.38 mol/l NH2OH methanolic solution at 80°C and then in a 0.1 mol/l NaOH aqueous solution at 30°C. The treatments were carried out by changing reaction periods to find the optimum conditions. The intrinsic adsorption rate of uranium from seawater with the amidoxime fibers was inversely proportional to fiber diameter, and the capacity was in the range of 120–350 mg per kg of dry fiber per day. The effective diffusivity of uranium in 1.5-denier amidoxime fiber immersed in seawater was 5 × 10–8 cm2/s. The strength of the fibers was not reduced by the NH2OH and NaOH treatment.
Using energy utilization diagrams, we can examine the exergy relation in a process system by representing the distribution of exergy loss and driving force for each part of the system graphically. This study makes it possible to automatically draw these diagrams for processes which include both gas and liquid phases by a simple program using a command MULTn. It requires only information about input streams, the reaction and its extent, and the temperature and pressure of the outlet stream, and information about a heat source or a sink. The basic features of output energy utilization diagrams are examined for the cases when the outlet stream is in equilibrium between gas and liquid phases and when it deviates from equilibrium. Also, another command MIXn is proposed to draw similar diagrams for the mixing of multiphase streams.
Energy utilization diagrams (EUDs) are applied to the design of reverse-type absorption chillers. They represent the distribution of both the exergy loss and the driving force in each part of the system. It is shown that the performance of the reverse cycle is quite high. in particular, installation of an auxiliary heat exchanger is expected to raise the efficiency much higher. The procedure for improving the process system by examining the displayed EUDs shows that EUDs are quite effective in designing process systems. Since only information of enthalpy and entropy is required, EUDs can be drawn in an early stage of system design and may become a powerful tool for technology assessment.