Hideki Tsuge

BUBBLE FORMATION FROM AN ORIFICE SUBMERGED IN LIQUIDS

The phenomena of the bubble formation from an orifice submerged in a liquid is classified according to their formation mechanisms and the estimation expressions of the bubble volume are reviewed The revised two-stage model of bubble formation accompanied by the pressure fluctuation in the gas chamber is presented and the results computed by this model are compared with the experimental results obtained for relatively wider range of gas chamber volume. Effects of some factors on the bubble volume, such as, gas chamber volume, orifice diameter, physical properties of gas and velocity of surrounding liquid are discussed

Bubble formation under constant-flow conditions

Abstract Bubble volumes and shapes formed from a constant-flow nozzle submerged in liquids were measured experimentally. By modifying the previous works, a new constant gas flow condition was proposed. A nonspherical bubble formation model under constant-flow conditions was developed, and the calculated volumes and shapes of bubbles agreed with both the present experimental results and the previous works.

Bubble formation at a nozzle submerged in viscous liquids having yield stress

Abstract The effects of operating conditions on bubble volume formed from a nozzle submerged in some viscous media with yield stress were experimentally investigated. Pressure fluctuations in the gas chamber accompanied by bubble formation as well as bubble growth curves were measured. By analysis of the time course of pressure change in the gas chamber, the dependency of the gas flow rate into the gas chamber and the chamber volume on the polytropic coefficient of gas in the gas chamber was discussed. To simulate the bubble formation at a single nozzle in a viscous medium having yield stress, the non-spherical bubble formation model was proposed. The calculated bubble volumes agreed relatively well with the experimental ones.

Ammonia absorption from a bubble expanding at a submerged orifice into water

Abstract To investigate the mechanism of gas absorption from a bubble containing soluble and insoluble components, a gaseous mixture of ammonia and nitrogen was bubbled into water. The growth curve, volume, surface area and shape of the growing bubbles were measured with parameters such as inlet gas composition, gas flow rate and gas chamber volume. The bubble volume decreased with the increasing composition of ammonia in a bubble, decreasing gas chamber volume and decreasing gas flow rate. To reasonably express the mass transfer from the bulk of a gas in a bubble to the bulk of a liquid, the overall mass transfer resistance was evaluated by the mass transfers in the gas phase, interface and liquid phase. The non-spherical bubble formation model combined with the overall mass transfer resistance estimated well experimental bubble shape, bubble volume at its detachment from an orifice, growth rate and mass transfer rate. Moreover, the change of concentration with bubble growth time and the fractional absorption during bubble formation were simulated.

Bubble formation at a single orifice in non-Newtonian liquids

Abstract The effects of various factors on the volumes and shapes of bubbles formed at a single orifice submerged in non-Newtonian liquids, such as physical properties of liquids, gas chamber volume, orifice diameter and gas flow rate were studied. To clarify the bubble formation mechanism, the bubble volume, bubble shape and gas chamber pressure during the bubble growth were measured simultaneously. A revised non-spherical bubble formation model was proposed to describe the bubble formation mechanism in non-Newtonian liquids. The bubble volume, bubble shape and pressure change in the gas chamber calculated by this model agreed well with the experimental results over a wide range of rheological characteristics of liquids.

Behavior of bubble formation in suspended solution for an elevated pressure system

The effects of various factors on the volumes of bubbles formed in suspended solutions under highly pressurized conditions, such as system pressure, orifice diameter, gas flow rate, gas chamber volume and solid particle concentration, were experimentally studied. A non-spherical bubble formation model considering the effects of solid particle concentration and the highly pressurized system is proposed in order to estimate bubble volumes.

Bubble formation in flowing liquid under reduced gravity

Abstract A great deal of research has been done regarding bubble formation from submerged orifices in liquids under the force of gravity for the design of gas-liquid or gas-liquid-solid contacting equipment. On the other hand, little research has been done concerning bubble formation under reduced gravity conditions. For the basic design of the chemical process systems or life-support systems in space stations and on other planets, it is important to clarify the effects of various factors on the volume and shape of bubbles formed at submerged orifices or nozzles under reduced gravity conditions. In order to disperse adequately bubbles in liquids for mass transfer or chemical reaction processes at relatively low gas flow rates under reduced gravity, it is necessary to force bubbles to become detached from nozzles by external forces. In this study, the liquid flow was used as the external force on bubble formation. The aim of this study is to clarify the behavior of bubble formation in flowing liquids under reduced gravity conditions. We experimentally investigated the effects of gas flow rate, liquid flow velocity, and liquid flow direction (cocurrent, countercurrent or cross-current flow) on bubble formation for a period of 1.2 s under reduced gravity conditions that were produced in the 10 m drop tower at the Hokkaido National Industrial Research Institute at Sapporo in Hokkaido. In order to describe theoretically the bubble formation in flowing liquids under reduced gravity conditions, a revised non-spherical bubble formation model was proposed and the calculated results of the bubble volume were compared with the experimental ones.

Reactive crystallization behaviour of calcium phosphate with and without whey protein addition

The reactive crystallization of calcium phosphate was studied by reacting potassium phosphate and calcium nitrate aqueous solutions in the batch system. When the solution has high supersaturation at the beginning of reaction, amorphous tricalcium phosphate (ACP), Ca3(PO4)2·nH20 was precipitated instantly as the initial solid phase. The formation of ACP depends on the ion activity product of ACP regardless of initial pH. ACP transforms to calcium phosphates such as dicalcium phosphate dihydrate (DCPD), CaHPO4·2H2O, hydroxyapatite (HAP), Ca5OH(PO4)3 and octacalcium phosphate (OCP), Ca8H2(PO4)6·5H2O. Effects of solution pH, reaction temperature and addition of whey protein on the behaviour of reactive crystallization of calcium phosphates have been studied. The precipitation diagram of calcium phosphates was obtained as a function of reaction temperature and initial solution pH, whose ranges were 15–50°C and 5–9. By the addition of whey protein isolate, the nucleation and growth of calcium phosphate were retarded. The existence of proteins slows down the reaction of calcium ions and phosphate ions. By the addition of WPI, the shape modification of DCPD and HAP was observed. DCPD became thicker, gathered in bundles and its surface was uneven and cracked. The surface state of HAP particles does not change, whereas the size changes slightly. The cubic form of HAP was also observed by addition of WPI, which may be formed by the crush after natural drying because HAP obtained was caked very hard by the addition of WPI.

Behavior of bubbles formed from a submerged orifice under high system pressure

The effects of various factors on the volumes and shapes of bubbles formed at a single orifice under highly pressurized conditions, such as system pressure, orifice diameter, gas flow rate and gas chamber volume, were studied. To clarify the bubble formation mechanism, the bubble shape during the bubble formation and bubble volume were measured. The experimental results were compared with the calculated ones by the revised non-spherical bubble formation model presented by the authors and they agreed qualitatively well.

Reactive crystallization of calcium carbonate in a batch crystallizer

Abstract Reactive crystallization of calcium carbonate by gas-liquid reactions were conducted in both a seeded and an unseeded batch crystallizer at unsteady state to clarify the crystallization mechanism. The crystallizer was a 1 liter gas sparged tank reactor with a turbine type impeller. The reactants used were an aqueous solution of calcium hydroxide and mixed gases of carbon dioxide and nitrogen. Crystal sampling was conducted at fixed time intervals to measure the changes of the crystal size distribution (CSD) and mean crystal size with reaction time. Measurements were made by scanning electron microscopy. The change of suspension density with reaction time was measured by pH meter. The experimental crystal growth rate was a power function of reaction time, while the nucleation rate was obtained theoretically from the mass balance as a function of reaction time, suspension density, and crystal growth rate. CSD and the change of suspension density with reaction time were obtained from these experimental equations, mass balance, and population balance. These results were compared with the experimental ones.