• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.10
• /
• pp.2595-2606
• /
• 1995

Buoyancy-assisted melting of an unconstrained ice in an isothermally heated horizontal enclosure was numerically analyzed in a range of wall temperatures encompassing the density inversion point. The problem as posed here involves two physically distinct domains each of which has its own scales and respective heat transfer mode. These two domains join at the junction where the liquid squeezed out of the film region flushes into the lower melt pool. Both of these domains have been treated separately in the literature by a patching technique which invokes several, otherwise unnecessary, assumptions. The present study eliminates successfully such a superfluous procedure by treating the film and lower melt pool regions as a single domain. As a result of this efficient solution procedure, the interaction of the water stream ejected at the junction and the natural convection in the melt pool could be clarified for different wall temperatures. Though limited by two-dimensionality, the present results conformed indirectly the earlier reported transition of the flow pattern, as the wall temperature was increased over the density inversion point. The transient evolution of the melting surface, the time rate of change in melt volume fraction, the local and temporal variation of the heat transfer coefficients are analyzed and presented.

• Korean Membrane Journal
• /
• v.3 no.1
• /
• pp.24-31
• /
• 2001

Ultrafiltration membranes base on copoly(amide-imide) derivatives were prepared by the phase inversion method and the factors determining the permeation characteristics of membrane were investigated. The permeation behavior was observed by the relative ratio of permeate flux (J$\_$t/)/pure water flux (J$\_$o/). The characteristics through membrane were measured using aqueous solution of poly(ethyleneglycol) (MW 2.0$\times$10$\^$4/) over a temperature range of 10∼90$\^{C}$. With increasing the operating temperature, the relative ratio of flux became high. All the membranes had good chemical stability. Copoly(amide-imide) membranes having various Permeation properties could be obtained. Further, it was proved that the membrane performances could be determined from the preparation conditions as well as various operating conditions.

• Membrane and Water Treatment
• /
• v.7 no.6
• /
• pp.555-571
• /
• 2016

Heavy metal contamination has attracted considerable attention during recent decades due to the potential risk brought about for human beings and the environment. Several adsorbent materials are utilized for the purification of contaminated water resources among which chitosan is considered as an appropriate alternative. Copper is a heavy metal contaminants found in several industrial wastewaters and its adsorption on porous and macroporous chitosan membranes is investigated in this study. Membranes are prepared by phase inversion and particulate leaching method and their morphology is characterized using SEM analysis. Batch adsorption experiments are performed and it is found that copper adsorption on macroporous chitosan membrane is higher than porous membrane. The iso-steric heat of adsorption was determined by analyzing the variations of temperature to investigate its effect on adsorption characteristics of macroporous chitosan membranes. Furthermore, desorption experiments were studied using NaCl and EDTA as eluants. The mechanism of copper adsorption was also investigated using XPS spectroscopy which confirms simultaneous occurrence of chelation and electrostatic adsorption mechanisms.

• Journal of Environmental Science International
• /
• v.8 no.1
• /
• pp.61-67
• /
• 1999

Silicone oil has organic and inorganic properties, and its skeleton is polysiloxane bonding that silicon is bonded hydrogen or organic group. Silicone compounds are very smooth and lubricant properties by low surface tension, low temperature dependence, and nonadhesive properties. Because of these properties, silicone compounds are used as many parts of chemicals, softener, smooth and libricant agents, water-repellent agent, and defoaming agent, etc. Emulsion was prepared with the inversion emulsification method which adopted the agent-in-oil method dissolving the polyoxyethylene(7) tridecyl ether(HLB 12.2) into methoxy terminated poly(dimethyl-co-methyl amino) siloxane and hydroxy terminated poly(dimethyl-co-methyl amino) siloxane in water. At this time, processed emulsion was almost microemulsion. When ratio of emulsifier increases, emulsion is stable bacuause microemulsion is solubilized by emulsion drop size and zeta-potential are decreased. But, when amount of electrolyte is increase, emulsion became unstable because emulsion drop size is increased.

• 한국해양학회지
• /
• v.18 no.1
• /
• pp.43-48
• /
• 1983

Oceanic temperature inversions, with unstable stratifications, are frequently founed in the surface layer of a few tens meters in the Japan Sea and the Yellow Sea in Winter. Mechanisms responsible for the generation of temperature inversions include the followings: (1) The nat heat loss at the sea suface requires an upward transport of heat from the interior of the ocean y convection, and this convection leads to the temperature inversions. (2) The downward propagation of the annual variation of the sea surface timperature, with an exponential decrease of amplitude and a linear change of phase with depth, generates the surface inversion layer in winter. (3) The cold water cdvection by Ekman drift, of which magnitude decreases exponentially with depth, generates temperature inversions for the three possible mechanisms mentioned above.

• Journal of the Korean earth science society
• /
• v.21 no.5
• /
• pp.541-552
• /
• 2000

The variations of physical properties due to inflow of seawater by sluice gates operation were observed in Shihwa Lake. The distributions of salinity and temperature were investigated at 11 stations during February, 1997 to July, 1998. The salinity of water mass in Shihwa Lake before gate operation was ranged below 15psu and strong stratification due to inflow of seawater was observed at the depth of 11 m. In July 1997, temperature difference of 10^{\circ}C$ was occurred between the surface and bottom water due to strong solar radiation. During October 1997 to February 1998, inversion of temperature distribution, which the temperature of bottom water was higher than that of surface water, was observed. In July 1997, temperature, salinity, current speed and current direction were investigated by RCM-7 at St.3 for 56 days. When sea water was intruded in Shihwa Lake, the symmetric distribution of temperature and salinity was observed and it seems to be resulted from inflow of seawater with low temperature and high salinity. After January 1998, salinity of Shihwa Lake was increased over 30psu due to continuous gate operation and the stratification was weakened.

• Journal of Environmental Science International
• /
• v.2 no.1
• /
• pp.17-26
• /
• 1993

The layer that is directly influenced by ground surface is called the atmospheric boutsdary layer in comparison with the free atmosphere of higher layer. In the boundary layer, the changes of wind, temperature and coefficient of turbulent diffusion in altitude are large and have great influences an atmospheric diffusion. The purpose of this paper is to express the structure and characteristics of development of mixed layer by using laboratory experiment and numerical simulation. Laboratory experiment using water tank are performed that closely simulate the process of break up of nocturnal surface inversion above heated surface and its phenomena are analyzed by the use of horizontally averaged temperature which is observed. The result obtained from the laboratory experiment is compared with theoretical ones from ; \textsc{k}-\varepsilon numerical model. The results are summarized as follows. 1) The horizontally averaged temperature was found to vary smoothly with height and the mixed layer developed obviously being affected by the convection. 2) The mean height of mixed layer may be predicted as a function of time, knowing the mean initial temperature gradient. The experimental values are associated well with the theoretical values computed for value of the universal constant $C_r$= 0.16, our $C_r$ value is little smaller than the value found by Townsend and Deardoru et al.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.4 no.1
• /
• pp.1-10
• /
• 2008

A magnetotelluric survey and geological survey have been performed to delineate deeply extended fracture systems at the geothermal field in Seokmo Island, Inchon, Korea. One borehole(BH-1) succeed to meet a large fracture system at the depth of 750 m where approximately $72^{\circ}C$ geothermal water is overflowing, while the other borehole(BH-2), which is about 200 m eastward from BH-1, failed to develop enough geothermal water even at the depth of 1,200m. Though there have been so many electric noise sources around the survey region, good quality of MT data above 1 Hz could be obtained with careful installation, remote reference processing. Inversion of MT data for two lines roughly perpendicular to the two major lineaments respectively show that the two lineaments are related to the fracture systems that are extended at least down to 1.5 km depth and inclined eastwards. From the interpretation, additional drilling for BH-2 is recommended and finally meet the fracture systems at the depth of 1,280 m and resulted in overflow of large amount of geothermal water of temperature $69.4^{\circ}C$ from BH-2.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.4
• /
• pp.602-611
• /
• 2013

We have investigated the influence of system composition and preparation conditions on the particle size of vitamin E acetate (VE)-loaded nanoemulsions prepared by PIC(phase inversion composition) emulsification. This method relies on the formation of very fine oil droplets when water is added to oil/surfactant mixture. The oil-to-emulsion ratio content was kept constant (5 wt.%) while the surfactant-to-oil ratio (%SOR) was varied from 50 to 200 %. Oil phase composition (vitamin E to medium chain ester ratio, %VOR) had an effect on particle size, with the smallest droplets being formed below 60 % of VOR. Food-grade non-ionic surfactants (Tween 80 and Span 80) were used as an emulsifier. The effect of f on the droplet size distribution has been studied. In our system, the droplet volume fraction, given by the oil volume fraction plus the surfactant volume fraction, was varied from 0.1 to 0.3. The droplet diameter remains less than 350 nm when O/S is fixed at 1:1. The droplet size increases gradually as the increasing the volume fraction. Particle size could also be reduced by increasing the temperature when water was added to oil/surfactant mixture. By optimizing system composition and homogenization conditions we were able to form VE-loaded nanoemulsions with small mean droplet diameters (d < 50 nm). The PIC emulsification method therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.43 no.4
• /
• pp.273-279
• /
• 2017

In this study, low viscous O/W (oil-in-water) nano-emulsion with fatty acid and fatty alcohol was prepared by phase inversion emulsification method using Tween 80 and Span 80 widely used in cosmetic products. The particle size of the nano-emulsion was increased as increasing the concentration of fatty alcohol in oil phase. Adjusting the HLB of mixed surfactants, a stable nano-emulsion with a narrow size distribution was produced. Similar change in viscosity and electrical conductivity in both systems containing fatty acid and fatty alcohol was shown in the vicinity of the phase inversion point. However, high viscosity was shown in a wide range of different aqueous fraction unlike the system consisting only oils and surfactants. The low viscous nano-emulsion with less than 100 nm droplet size was stable for one month or more at room temperature. O/W nano-emulsions with low viscosity containing fatty acid or fatty alcohol produced by low-energy emulsification method can be widely used as formulations of cosmetics.