• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.8
• /
• pp.759-765
• /
• 2013

This study proposes the characteristics of the pressure drop in a compressible fluid through porous media for application to a porous injector in a liquid rocket engine in order to improve the uniformity of the drop size distribution and the mixing performance of shear coaxial injectors. The fluid through the porous media is a Non-Darcy flow that shows a Nonlinear relation between the pressure drop and the velocity at high speed and high mass flow rate. The pressure drop of the Non-Darcy flow can be derived using the Forchheimer equation that includes the losses of viscous and inertia resistance. The permeability and Ergun coefficient represented as a function of the pressure drop and pore size can be applied to the porous injector, where the fluid through the porous media is compressible. A generalized correlation between the pressure drop in relation to the pore size was derived.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.6
• /
• pp.662-669
• /
• 2015

There has been an increased interest in the mitigation of wax deposition because wax, which usually accumulates in subsea oil-production systems, interrupts stable oil production and significantly increases the cost. To guarantee a required oil flow by mitigating wax deposition, we need to obtain a reliable estimation of the wax deposition. In this research, we perform simulations to understand the major mechanisms that lead to wax deposition, namely molecular diffusion, shear stripping reduction, and aging. While the model variables (shear reduction multiplier, wax porosity, wax thermal conductivity, and molecular diffusion multiplier) can be measured experimentally, they have high uncertainty. We perform an analysis of these variables and the amount of water and gas in the multiphase flow to determine these effects on the behavior of wax deposition. Based on the results obtained during this study for a higher wax porosity and molecular diffusion multiplier, we were able to confirm the presence of thicker wax deposits. As the shear reduction multiplier decreased, the thickness of the wax deposits increased. As the amount of water increased, there was also an increase in the amount of wax deposits until 40% water cut and decreased. As the amount of gas increased, the amount of wax deposits increased because of the loss of the light hydrocarbon component in the liquid phase. The results of this study can be utilized to estimate the wax deposition behavior by comparing the experiment (or field) and simulation data.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.1
• /
• pp.13-24
• /
• 1988

This paper is concentrated on the development of oxygen transfer system by U-tube deep shaft in biological fluidised bed process. The depth of the shaft is 32 m, it is composed of downcomer and riser. Not only flow pattern and oxygen transfer in the deep shaft but also oxygen limitation in biofilm and oxygen utilization in biological fluidised bed are investigated. In this investigation, driving force for liquid circulation in the deep shaft is affected by air injection depth and gas hold-up in downcomer. Flow pattern of the deep shaft is revealed to plug flow. When flow velocity in the deep shaft is maintained to 0.52 m/sec, $K_La$ value is peak at 25~30 m depth in riser. The efficiency of dissolved oxygen supply which passed from the deep shaft to biological fluidised bed is estimated to 56~81 % in the organic wastewater treatment using the deep shaft and when dissolved oxygen concentration is 9.2 mg/l and over, limiting factors of flux and substrate within biofilm are organic materials. Terefore, organic loadings could be increase without decreasing of BOD removal efficiency.

• Polymer(Korea)
• /
• v.31 no.3
• /
• pp.215-220
• /
• 2007

The control of the surface energy by electrohydrodynamic force provides electrospraying with various potential advantages such as simple particle size control, mono-dispersity, high recovery, and mild processing conditions. The advantages are quite helpful to improve the stability of protein drug and control its release. Herein, the nano-encapsulation of protein drugs using electrospraying was investigated. Albumin as a model protein was processed using uniaxial and co-axial electrospraying, and chitosan, polycaporlactone (PCL), and poly (ethylene glycol) (PEG) were used as encapsulation materials. The major processing parameters such as the conductivity of spraying liquids, flow rate, the distance of electrical potential gradient, etc were measured to obtain the maximum efficiency. In the chitosan systems, mean particles size decreases as flow rate and the distance between nozzle and the collecting part decreases. In the uniaxial technique of the PCL systems, mean particles size decreases as flow rate decreases. In the coaxial technique of the PCL systems, it was found that the particles size gets larger under the application of the higher ratio of inner-to-outer liquid flow rates. The primary particles formed out of an electrospraying nozzle showed narrow particle size distribution, but once they arrived to the collecting part, aggregation behavior was observed obviously. Efficient nano-encapsulation of albumin with PCL, PEG, and chitosan was conveniently achieved using electrospraying at above 12 kV.

• Journal of the Korean Institute of Gas
• /
• v.26 no.4
• /
• pp.9-17
• /
• 2022

This paper is the continuation of our previous paper, which we refer to as numerical analysis of phase behavior and flow properties in an injection tubing during gas phase CO₂ injection. Our study in this paper show the results during supercritcal CO₂ injection under the same project. Geological CO₂ storage technology is one of the most effective method to decrease climate change due to high injectivity and storage capacity and economics. A demonstration-scale CO₂ storage project was performed in a deep aquifer in the Pohang basin, Korea for a technological development in a large-scale CO₂ storage project. A problem to consider in the early stage design of the project was to analyze CO₂ phase change and flow characteristics during CO₂ injection. To solve this problem, injection conditions were decided by calculating injection rate, pressure, temperature, and thermodynamic properties. For this research, we simulated and numerically analyzed CO₂ phase change from liquid to supercritical phase and flow characteristics in injection tubing using OLGA program. Our results provide discharge pressure and temperature conditions of CO₂ injection combined with a pressure of an aquifer.

• Applied Chemistry for Engineering
• /
• v.21 no.1
• /
• pp.71-75
• /
• 2010

The efficient performance of absorber is of great importance for the absorption heat pump cycle. The experimental study of absorber with spiral tube of tangential feeding of liquid phase has been investigated using methanol-glycerine as a working fluid. The effect of change in absorber operating conditions was analyzed to improve the performance. The increase in solution flow rate and cooling flow rate positively affects the absorber performance while an increse in the solution concentration negatively affects the absorber performance. The results showed that mass absorption flux was in the range of $0.2{\sim}0.6kgm^{-2}sec^{-1}$, the solution heat transfer coefficient between 1.6 and $4.2kwm^{-2}K^{-1}$, the absorber thermal load from 0.9 to 1.5kw and the mass transfer coefficient from 0.9 to 1.7 m/sec.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.3
• /
• pp.265-270
• /
• 2004

Experiment study on a down scaled two-phase catalytic reactor is presented. As a preliminary step for the development of catalytic reactor, nano-particulate catalyst was prepared. Perovskite La$\_$0.8/Sr$\_$0.2/CoO$_3$is chosen and synthesized as a catalyst considering superior catalytic performance in reduction and oxidation process where oxygen is involved among the reagent. Reactor that has a scale of 2${\times}$10${\times}$25mm was made by machining of A1 block as a layered structure considering further extension to micro-machining. Hydrogen peroxide of 70wt% was adopted as reactant and was provided to the reactor loaded with 1.5 g of catalyst. Reactant flow rate was varied by precision pump with a range of 0.15cc/min to 17.2cc/min. Temperature distribution within reactor was recorded by 3 thermocouples and total amount of liquid product was measured. Temperature distribution and factors that affect temperature were observed and relation between temperature distribution and production rate was also analyzed. Relative time scale plays a significant role in the performance of the reactor. To obtain steady state operation, appropriate ratio of flow rate, catalyst mass and reactor geometry is required and furthermore to get more efficient production rate temperature distribution should be evenly distributed. The database obtained by the experiment will be used as a design parameter for micro reactor.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.2
• /
• pp.190-198
• /
• 2008

In this stduy, the column experiments were carried out assuming the soil was contaminated by leakage of gasoline containing MTBE from USTs and pipes around gas stations. Then, characteristics of MTBE transport in the soil were investigated using CXTFIT program. The column experiments with different soil properties, moisture content, organic matter content and flow rate were carried out. Some parameters(D, R, $\beta$, $\omega$) used in two-site non-equilibrium adsorption model were obtained from measuring the MTBE concentration in injection-liquid and in effluent and using CXTFIT program. In addition, The characteristics of MTBE transport in the soil was found using BTCs and obtained parameters. Consequently, the advection decreased as the increase of the content of fine particle and organic, while the MTBE transport by advection was enhanced as increasing flow rate and moisture content.

• Journal of Energy Engineering
• /
• v.8 no.2
• /
• pp.325-332
• /
• 1999

When a rotating heat pipe is in operation, liquid condensate returns from the condenser to the evaporator along the inside surface by both components of gravitational and centrifugal forces. It was known that its performance was largely dependent on how to increase the flow rates of condensate and keep the condensate film thickness as thin as possible. Most of research works were focussed on this goal, and various inner wall structures such as tapered wall, stepped wall or coil inserted pipe etc. were developed. In the present study, a stepped wall structure with 3 internal grooves in the condenser and adiabatic zone was examined. For this system, the condensate would flow down to the evaporator through the grooves, resulting a reduced film thickness over the condenser surface. Experimental data showed an enhancement of heat transfer coefficient in the condenser zone. An analytical solution to the condensate film thickness showed that the analytically calculated values of heat transfer coefficient were considerably higher than the experimental data.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.1
• /
• pp.46-52
• /
• 2008

Oils and chlorinated solvents leaking to the subsurface are entrapped in the soil pore and these are called as nonaqueous phase liquids (NAPL). NAPL entrapped in porous media acts as a continuous source for surface and ground water contamination. This study visualized dissolution of trichloroethylene (TCE) entrapped in porous media and quantified the velocity of TCE dissolution using an image analysis technique. As the water velocity increased, the level of dissolution increased. The results imply that a TCE contaminated region having a high infiltration rate and groundwater velocity may result in severe groundwater contamination. Microscopic images of TCE entrapped in porous media showed that TCE present in the preferential flow paths was easily dissoluted into the water phase. However, TCE present in the stagnant flow region was visualized for long time. The results imply that TCE would be still present in the soil if TCE is detected in goundwater.