• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.929-936
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• 2013

The saturator and injection nozzle are important facilities on the dissolved air flotation process. To increase the formation of micro bubble, it is required to improve the air dissolving performance in the saturator and keep the pressure uniform from the saturator to the nozzle. This study aimed to evaluate the performance of the saturator and the hydraulic effect of the nozzle and the pipe structure. The air volume concentration, bubble size and bubble residual time were measured in the test. The saturator, which had mounted with the spray nozzle, showed a good performance for bubble formation. Also, the characteristics of micro bubble formation were influenced by pressure uniformity and flow velocity through the orifice in the nozzle.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.151-158
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• 2011

Bubbles within the foamed concrete manufactured by pre-foaming method is the main factor which affects the physical properties of foamed concrete such as density, strength, and porosity. Although many researches on foamed concrete have been continuously carried out, insufficient number of researches on the properties related to bubbles in the foamed concrete has been performed except for chemical application related researches. In order to make an optimal foamed concrete, study on the bubble properties must be pursued. In order to effectively implement bubbles in the manufacturing of foamed concrete, the bubble properties must be estimated. In this study, in order to determine the bubble properties, examination of the bubble properties according to types and foaming agent concentration was performed. An foaming agent used for this test were anionic surfactant, rosin, and protein system with the foaming agent concentration range of 0.05~13%. Test parameters considered in the study were foaming rate, foam volume, drainage solution volume, and bubble size. The study results showed that, regardless of foaming agent type, higher concentration of foaming agent showed an increase in the foaming rate. Also, the results showed that concentration of foaming agent affected bubble size, drainage solution volume change, and bubble distributions. With respect to the stability of the bubble, protein foaming agent was better than anion surfactant or rosin foaming agent. With respect to the bubble shape, anion surfactant and rosin formed bubbles had polygon shape where as protein formed bubbles had spherical shape.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.549-555
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• 2017

The purpose of this study is to investigate how ozone-dissolution-tank structure affects micro-ozone-bubble distribution, energy consumption and water treatment efficiency. The partition walls inside the ozone-dissolution-tank generate pressure changes, shear forces, and swirling flows, which change the size of the bubble diameter. The size of the bubble diameter differs by 10.5% depending on the partition walls. Changes in ozone-bubble diameter are related to energy consumption. As the ozone-bubble becomes smaller, the bubble generation energy increases, but the ozone production energy decreases as the dissolution efficiency increases. Therefore, an ozone-dissolution-tank should be determined by means of an optimal condition producing a micro-ozone-bubble with a minimum sum of bubble generation energy and ozone production energy. The energy consumed to inject the same amount of ozone into the effluent differs by 2.5% depending on the partition walls. However, considering the water treatment efficiency, the conditions for selecting the ozone-dissolution-tank are variable. This is because the free radicals that increase as the ozone-bubble gets smaller are very efficient for water treatment. Even at the same ozone injection concentration, the water treatment efficiency differs by 10.4% according to the partition walls. Therefore, we have studied ozone-dissolution-tank structure which produces reasonable ozone-bubble considering water treatment efficiency and energy efficiency.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.604-608
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• 2004

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better breakup of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.462-469
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• 2010

Gas-liquid 2 phase processes are usually used in chemical, biochemical, environmental engineering and food process. For optimizing these processes, understanding bubble's precise movement and shape are needed. Bubble's movement and shape are effected by liquid's properties-viscosity, surface tension and bubble's properties-size, velocity. This paper deals with experimental data of bubble's movement and shape in high viscous silicone oil. Also, drag coefficient and deformation factor given by other researcher's papers and books are used to predicting and comparing bubble's terminal velocity, drag coefficient, deformation factor and shape with experimental value. Experimental data show that bubble moves faster when it moves in lower viscous silicone oil and it's drag coefficient is bigger when it moves in high viscous silicone oil. Bubble's shape is close to sphere when moving in high viscous silicone. Formulas proposed by Batchelor expect most accurate prediction for bubble's velocity and drag coefficient. Bubble's 2D shape predicted by Batchelor's energy balance, drag coefficient and deformation factor show excellent agreement with experimental bubble's 2D shape.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.996-1003
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• 2004

The bubble motion during nucleate boiling in a microchannel is investigated by numerically solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the evaporative heat flux from the thin liquid film that forms underneath a growing bubble attached to the wall is incorporated in the analysis. Based on the numerical results, the effects of channel size, contact angle, wall superheat and waiting period on the bubble growth and heat transfer in a microchannel are quantified.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.731-738
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• 2010

Cavitation is described by formation and collapse of the bubbles in a liquid when the ambient pressure decreases. Formed bubbles grow and collapse by change of pressure, and when they collapse, shockwave by high pressure is generated. In general, bubble behavior can be described by Rayleigh-Plesset equation under adiabatic or isothermal condition and hence, phase shift by the pressure change in a bubble cannot be considered in the equation. In our study, a numerical model is developed from the mathematical model considering the phase shift from the previous study. In the developed numerical model, size of single spherical bubble is calculated by the change of mass calculated from the change of the ambient pressure in a liquid. The developed numerical model is verified by a case of liquid flow in a narrow channel.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.201-207
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• 2004

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contact considered by the researchers to play a important role for DAF performance. It is hard to make up conceptual model through simple mass balance for estimating collision efficiency in the contact zone because coupled behavior of the solid-liquid-gas phase in DAF system is 90 complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, the standard $k-{\varepsilon}$ mode I(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widely accepted and the coefficients for the model are well established. Particle-bubble collision efficiency was calculated using predicted turbulent energy dissipation rate and gas volume fraction. As the result of this study, the authors concluded that bubble size and recycle ratio play important role for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreement with measured removal efficiency in the contact zone. Also, simulation results indicated that collision efficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collision efficiency according to the decrease of the bubble size.

• Journal of Korea Society of Industrial Information Systems
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• v.29 no.1
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• pp.117-123
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• 2024

Bubbles generated in water receive an upward buoyant force due to the density and pressure difference of the surrounding fluid. Additionally, the behavior, shape, and heat exchange process of bubbles vary depending on the viscosity, surface tension, rising speed, and size difference with the surrounding fluid. In this study, we modeled speed, and heat transfer of a high-temperature single bubble rising in a cylindrical water tank. For this purpose, velocity, and temperature of the bubbles were calculated using theoretical equations, to be compared with numerical simulation results. The numerical analysis was performed using a commercial software, and the stability of the numerical analysis with mesh size was confirmed through calculation of the grid convergence index. The numerical analysis of the rising speed and temperature of a single bubble showed the values to converge when the minimum cell size was 1/160 of the bubble diameter, and the temperature decrease was confirmed to be the same as that of the surrounding fluid within 0.05 seconds.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1201-1206
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• 2004

Sonoluminescence (SL) characteristics such as pulse shape, radiance and spectrum radiance from submicron bubbles were investigated. In this study, a set of analytical solutions of the Navier-Stokes equations for the gas inside bubble and equations obtained from mass, momentum and energy equations for the liquid layer adjacent the bubble wall were used to estimate the gas temperature and pressure at the collapse point, which are crucial parameters to determine the SL characteristics. Heat transfer inside the gas bubble as well as at the liquid boundary layer, which was not considered in the most of previous studies on the sonoluminescence was taken it into account in the calculation of the temperature distribution inside the bubble. It was found that bremsstrahlung is a very possible mechanism of the light emission from either micron or submicron bubbles. It was also found that the peak temperature exceeding $10^{6}$ K in the submicron bubble driven at 1 MHz and 4 atm may be due to the rapid change of the bubble wall acceleration near the collapse point rather than shock formation.