• Nuclear Engineering and Technology
• /
• v.26 no.1
• /
• pp.108-118
• /
• 1994

A semi-empirical correlation has been developed for adiabatic interfacial friction factors in a long horizontal air-water countercurrent stratified flow conditions. Using a pipe and duct test sections, a series of experiments hate been conducted varying non-dimensional water depth and flow rates of air. On the basis of simultaneous measurement of the main flow parameters in a horizontal pipe and a duct, a semi-empirical correlation for the interfacial friction factor in a stratified flow regime has been developed employing a new concept of surface roughness in wavy flow. A total of 201 data point, including 15 concurrent pipe flow test data of others, have been used in the present analysis. A comparison between the data and the predictions of the present correlation shows that the agreement is within $\pm$30%.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.8
• /
• pp.677-682
• /
• 2015

We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.

• Journal of Korean Society of Water and Wastewater
• /
• v.29 no.1
• /
• pp.89-96
• /
• 2015

Smart water grid is a water network with communication to save water and energy using various water resources. In smart water grid, water product from the various sources can be blended to be supplied to end-users. The product water blending was reported by literatures while feed water blending has been rarely reported so far. In this work, a commercial reverse osmosis (RO) system design software provided by a membrane manufacturer was used to elucidate the effect of feed water blending on the performance of seawater reverse osmosis (SWRO) plant. Fresh water from exisiting water resource was assumed to be blended to seawater to decrease salt concentration of the RO feed water. The feed water blending can simplify the RO system from double to single pass and decrease seawater intake amount, the unit prices of the RO system components including high pressure pump, and operation risk. Due to the increase in RO plant capacity with the feed water blending, however, the RO membrane area and total power consumption increase at higher water blending rates. Therefore, a specific benefit-cost analysis should be carried out to apply the feed water blending to SWRO plants.

• Membrane and Water Treatment
• /
• v.8 no.4
• /
• pp.323-336
• /
• 2017

The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute permeation was carried out under applied pressure of 5 bar at $25^{\circ}C$. Surface properties of TFC membrane were characterized by ATR-FTIR, SEM and AFM. The performance test indicated that 3.5 wt% of MPD, 0.35 wt% of TMC and curing temperature of $75^{\circ}C$ are the optimum conditions. Moreover, the permeate flux was $4.3{\frac{L}{m^2\;h}}$ and acetic acid rejection was about 43% at these conditions.

• Advanced Composite Materials
• /
• v.16 no.4
• /
• pp.299-314
• /
• 2007

In the present study, natural fibers (jute, kenaf and henequen) reinforced thermoplastic (poly(lactic acid) and polypropylene) and thermosetting (unsaturated polyester) matrix composites were well fabricated by a compression molding technique using all chopped natural fibers of about 10 mm long, respectively. Prior to green composite fabrication, natural fiber bundles were surface-treated with tap water by static soaking and dynamic ultrasonication methods, respectively. The interfacial shear strength, flexural properties, and dynamic mechanical properties of each green composite system were investigated by means of single fiber microbonding test, 3-point flexural test, and dynamic mechanical analysis, respectively. The result indicated that the properties of the polymeric resins were significantly improved by incorporating the natural fibers into the resin matrix and also the properties of untreated green composites were further improved by the water treatment done to the natural fibers used. Also, the property improvement of natural fiber-reinforced green composites strongly depended on the treatment method. The interfacial and mechanical results agreed with each other.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.8
• /
• pp.2005-2014
• /
• 2009

There are several methods to fabricate Polymer Dispersed Liquid Crystal(PDLC) films. One of them, so-called Nematic Curvilinear Aligned Phase(NCAP) film, is based on emulsion technology. To produce NCAP systems various water soluble polymers, such as partially hydrolyzed polyvinylalcohol(PVA) and polyvinyl pyrrolidone(PVP), which can form stable emulsion of liquid crystal(LC) without any stabilizers were used. In this work, we studied the dependence of emulsion stability on nature and composition of copolymers composed of water-soluble and water-insoluble moiety. We found that interfacial surface tension depends on the composition of comonomer, the copolymer concentration in the water, and the nature of hydrophobic chain. The Acrylamide -styrene(AA-ST) copolymer showed the lowest interfacial surface tension among the tested copolymers at the same concentration. Since the interfacial surface tension decreases with increasing the compatibility of copolymer with LC phase the AA-ST copolymer has the best compatibility with LC molecules. It is believed that molecules adsorbing easily on the surface of LC droplets allows the LC emulsion system to be more stable.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.432.1-432.1
• /
• 2016

We demonstrated that the power conversion efficiency (PCE) of bilayer solar cell was significantly enhanced by inserting interfacial layer between the organic bilayer film and the Al electrode. Moreover, the water contact angle shows that the bilayer solar cells suffer from the undesirable surface component which limits the charge transport to the Al electrode. The AFM measurement has revealed that the pre- and post-thermal annealing treatments results in different morphologies of the interfacial layer which is critical for the higher PCE of the bilayer solar cells. Furthermore we have investigated the electrical properties of the bilayer solar cells and obtained insights into the detailed device mechanisms. The transient photovoltage measurements suggests that the significantly enhanced Voc is caused by reducing the recombination at the interface between the organic films and the Al electrode. By inserting the TiO2 layer between the bilayer film and Al electrode, the open circuit voltage (Voc) was increased from 0.37 to 0.66V. Consequently, the power conversion efficiency (PCE) of bilayer solar cells was significantly enhanced from 1.23% to 3.71%. As the results, the TiO2 interfacial layer can be used to form an ohmic contact layer, serveing as a blocking layer to prevent the penetration of the Al, and to reduce the recombination at the interface.

• Journal of Adhesion and Interface
• /
• v.8 no.3
• /
• pp.9-15
• /
• 2007

The interfacial evaluation of surface modified Jute fiber/polypropylene (PP) composites before and after hydration was investigated using micromechanical test and dynamic contact angle measurement. The IFSS of alkaline and silane-treated Jute fiber/PP composites increased, whereas after hydration, the IFSS of the untreated, alkaline- and silane-treated Jute fibers/PP composites decreased due to swelled fibrils by water infiltration. The interfacial adhesion of silane treated fiber/PP composites was higher than alkaline-treated or the untreated cases. The surface energies of Jute fiber treated under various conditions were obtained using dynamic contact angle measurement. Especially after hydration, the thermodynamic work of adhesion was calculated by considering water interlayer, which indicated the stability of IFSS between silane treated Jute fiber and PP matrix showing better than others.

• Nuclear Engineering and Technology
• /
• v.38 no.1
• /
• pp.1-10
• /
• 2006

The interaction and mixing of high-temperature melt and water is the important technical issue in the safety assessment of water-cooled reactors to achieve ultimate core coolability. For specific advanced light water reactor (ALWR) designs, deliberate mixing of the core-melt and water is being considered as a mitigative measure, to assure ex-vessel core coolability. The paper provides the background of past experiments as well as key fundamentals that are needed for melt-water interfacial transport phenomena, thus enabling the development of innovative safety technologies for advanced LWRs that will assure ex-vessel core coolability.

• Journal of Microbiology and Biotechnology
• /
• v.9 no.1
• /
• pp.32-38
• /
• 1999

A biosurfactant produced by Tsukamurella sp. 26A was purified by procedures including acid precipitation, ethylacetate extraction, and adsorption chromatography. The purified biosurfactant reduced the surface tension of water from 72 mN/m to 30 mN/m at a concentration of 250 mg/l, whereas the minimum interfacial tension against n-hexadecane was lowered to 1.5 mN/m at a concentration of 40 mg/i. The compound stabilized oil-in-water emulsions with a variety of commercial oils and had strong emulsification and stabilization activities when compared to those of commercial emulsifiers and stabilizers. Surface tension was stable over a broad range of pH (2-12) and temperature ($100^{\circ}C$, 3h). The biosurfactant was identified as glycolipid having a hydrophilic moiety of trehalose.