• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.5
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• pp.49-54
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• 2011

Curtain coating has been considered as the best coating technology because it is a coating technology that forms contour coating layer with better coverage. To increase the curtain stability surfactants are being used. In this study, the effect of a surfactant on the stability of curtain coating colors was examined by evaluating dynamic surface tension with a bubble surface tensiometer. Di-2-ethylhexyl sodium sulfosuccinate was used as a surfactant since it showed low dynamic surface tension at low surface age. And we evaluated the influence of surfactant on coating color properties including surface tension, viscosity and curtain stability. The surface tension of coating color was decreased when surfactant addition was increased up to 0.5 pph, but it was leveled off at 0.3 pph of surfactant addition. With the increase of surfactant addition rate, viscosity of coating color were increased. Micelles formed by surfactant contributed to the increase of the viscosity. Curtain stability was improved with the addition of surfactant until it reached up to 0.5 pph. Excessive addition of surfactant (> 0.5 pph) didn't improve curtain stability. This was attributed to Marangoni effect(self-healing) and decreasing of curtain thickness.

• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.270-276
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• 2016

This study analysed overall heat transfer coefficient, heat transmission, and rate of indoor air heating provided by water curtain in order to determine the heat transfer characteristic of double-layered greenhouse equipped with a water curtain system. The air temperatures between the inner and outer layers were determined by the water flow rate and inlet water temperature. Higher water flow rate and inlet water temperature resulted in the increased overall heat transfer coefficient between indoor greenhouse air and water curtain. However, it was found that with higher levels of water flow rate and inlet water temperature, indoor overall heat transfer coefficient was converged about $10W{\cdot}m^{-2}{\cdot}^oC^{-1}$. The low correlation of overall heat transfer coefficient between water curtain and air within double layers was likely because the combination of greenhouse shape, wind speed and outdoor air temperature as well as water curtain affected the heat transfer characteristics. As water flow rate and inlet water temperature increased, the heat transferred into the greenhouse by water curtain also tend to rise. However it was demonstrated that the rate of heat transmission from water curtain into greenhouse with water curtain system using underground water was accounted for 22% to 28% for total heat lost by water curtain. The results of this study which quantify heat transfer coefficient and net heat transfer from water curtain may be a good reference for economical design of water curtain system.

• Solar Energy
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• v.9 no.1
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• pp.22-29
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• 1989

A simulation model of plastic greenhouse was developed to evaluate the insulation effect of thermal curtain. Change in thermal environment with and without thermal curtain was verified through experiments, which agreed with the predicted values satisfactorily. About 18 to 20% of energy was saved in the plastic greenhouse by employing the P.E. film thermal curtain. Employing P.E. film thermal curtain also raised the temperature of the covering film and inner air by $1^{\circ}C$ and $1.5{\sim}1.8^{\circ}C$, respectively.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.131-139
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• 2018

The preparation of repeatable and uniformly reconstituted soil specimens up to the specified conditions is an essential requirement for the laboratory tests. In this study for large samples replication, the simultaneous usage of the traveling pluviation and curtain raining technique is used to develop a new method, called the curtain travelling pluviator (CTP). This simple and cost effective system is based on the air pluviation approach, whilst reducing the sample production time, can reproduce uniform samples with relative densities ranging from 25% to 96%. In order to investigate the resulting suitability and uniformity from the proposed method, a series of tests is performed. The effect of curtain traveling velocity, curtain width, drop height, and flow rate on the parameters of the sample is thoroughly investigated. Increase in the curtain velocity and drop height leads to the increase in relative density for the sand specimen. Increase in curtain width typically resulted in the reduction of relative density. Test results reveal that the terminal drop height for the sand specimen in this study is more than 500 mm. Relative density contour lines are presented that can be utilized in optimizing the drop height and curtain width parameters. Sample uniformity in the vertical and horizontal orientation is investigated through the sampling containers. Increasing relative density tends to result in the higher sample repeatability and uniformity.

• Journal of the Korean housing association
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• v.15 no.3
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• pp.101-108
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• 2004

To find more efficient exhaust effect, air curtain of upward or downward trend in gas table and left or right side of range hood were made. As result that film vapor from range hood lower part by digital camera, the air current change by moving existence and nonexistence of exhaust fan and direction of air curtain were known. Under all experiment condition, upward air curtain superior exhaust performance.

• The KSFM Journal of Fluid Machinery
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• v.12 no.5
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• pp.25-32
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• 2009

A study is conducted to improve the suction performance on suction devices which are used to remove polluted air generated by welding or machining process in a spacious working place of industry. Air-curtain is applied around the inlet of suction duct to interrupt the inflow of fresh air from the downstream region where is located opposite to the polluted air source. Two different air-curtain devices, such as a $45^{\circ}$ backward and a fully backward, are adopted. Suction region is experimentally investigated by measuring the suction velocities using a hot-wire anemometer. Contours of the suction velocity are compared with the computed results. The suction condition is selected to 110,000 Reynolds number which is widely used on typical suction devices, and a width of blowing passage for creating the air-curtain is chosen to 9.38% of the suction duct diameter. The experimental results show that the suction performance obtained with the $45^{\circ}$ backward air-curtain was better than that obtained with the fully backward air-curtain. On the suction duct using the $45^{\circ}$ backward air-curtain, the suction region estimated on basis of the 0.4m/sec is improved by 66% at the same input power.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.5
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• pp.74-82
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• 2010

Curtain stability without curtain contraction is critical for a successful operation in curtain coating, and this can be influenced by the change in particle dynamics and rheological properties of coating colors. In this study, polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) were added to control the rheology of GCC based curtain coating colors. Surface tension was increased slightly with increasing content of cobinder. Shear-thinning of viscosity was more pronounced for the CMC containing GCC coating colors. Complex modulus decreased when small amount of PVA was used as a cobinder, but it increased in other coating colors. Extensional viscosity was increased with increasing of the cobinder content, but CMC was more effective. Results indicate that pigment interaction with PVA is different from that with CMC. Dispersibility of coating colors was improved due to steric stabilization when small amounts of PVA was used, but flocculation occurred by bridging when the amount of PVA was increased. Dispersibility of coating colors was improved when small amount of CMC was added, while flocculation was observed by depletion effect when the concentration of CMC was increased in coating colors. Addition of cobinders at proper levels gave positive effects both in rheological properties and curtain stability. On the other hand, excessive amount of cobinders caused particle flocculation and this resulted in rheological and curtain stablity problems.

• Journal of Environmental Impact Assessment
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• v.21 no.1
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• pp.25-39
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• 2012

This study was aimed to assess the effects of additional installation of two different types of weirs, one is a curtain-type weir and another is a submerged-type weir, on the control of algal growth in Daechung Reservoir. A two-dimensional(2D) coupled hydrodynamic and eutrophication model that can accommodate vertical movement of the curtain weir following the water surface variations was verified using field data obtained in two distinctive hydrological years; dry(2008) and wet(2010). The model adequately simulated the temporal and spatial variations of water temperature, nutrients and algal(Chl-a) concentrations during the periods. The effectiveness of curtain weir on the control of algal bloom was evaluated by applying the model to 2001(dry year) and 2010 assuming 6 different scenarios according to installation locations. The curtain weirs that already installed at 3, 5, 7 sites(scenario C-2) showed significant effect on the control of algal growth in the reservoir; the reduction rates of algal concentration were placed in the range of 7.5~31.5% and 9.1~44.9% for 2001 and 2010, respectively. However the simulation results revealed that additional installation of curtain weirs(scenario C-3~C-6) in the bay area (choosori) have marginal effect. The effectiveness of submerged weir was evaluated against 2010 assuming 7 different scenarios according to installation locations, but all scenarios(S-1~S-7) showed neglectable or negative effect on the control of algal growth.

• Journal of the Korean Society of Safety
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• v.38 no.3
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• pp.43-50
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• 2023

Silicone tetrachloride (SiCl₄) leak accidents cause enormous human and environmental damage because it is highly toxic. Some handling facilities use water curtains to reduce the impact range of SiCl₄. Although the water curtain is known as one of the most efficient technologies for post-release mitigation, its effect on reducing SiCl₄ concentration needs to be investigated scientifically and quantitatively. In this study, three-dimensional computational fluid dynamics (CFD) was used to investigate the physical and chemical effects of water curtains as a release-mitigation system for SiCl₄. SiCl₄ is released and dispersed five seconds prior to the operation of the water curtain. Once the water curtain works, the SiCl₄ reacts chemically with the water and its concentration decreases rapidly; it reaches an emergency response planning guidelines level 2 (ERPG-2) of 5 parts per million (ppm) at about 570 m. We observed, however, that the physical effect of water curtains on reducing SiCl₄ concentration is insignificant when the chemical effect is eliminated. These results are crucial since they can be a scientific and quantitative basis for the 'technical guidelines for estimating the accident affected range'. In order to protect the public from chemical accidents, more toxic gas mitigation technologies need to be developed.

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.5
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• pp.80-89
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• 2022

In order to solve the limitations of horizontal thermal environment improvement, this study compared the thermal environment of the indoor and outdoor of a building in summer according to the presence or absence of a green curtain, a vertical greening method. In the summer of 2021, the air temperature, relative humidity, wind speed, and shortwave and longwave radiation were measured at a central point inside a building and the grass field outside of the building to determine the human thermal sensation index, PET and UTCI. As a result, the green curtain showed an average 1.6℃ cooler air temperature during the daytime, but it did not have an effect at night. For relative humidity, it showed higher humidity indoors by an average of 5.6% and 1.0% during the daytime and at night, respectively. Wind speed was 1.4-1.8 ms^-1 and 1.4-1.5 ms^-1 higher outdoors on average during the daytime and at night, respectively, showing a high value outdoors regardless of whether a green curtain was installed. The green curtain showed an average indoor mean radiant temperature reduction effect of 4.7℃ during the daytime, but it did not have an effect at night. In PET and UTCI, the green curtain reduced the indoor PET by about a 1/3 level, an average of 2.1℃, and the indoor UTCI by about a 1/6 level, an average of 1.1℃, during the daytime. However, no effects appeared in PET and UTCI at night. For landscape planning, a green curtain can effectively modify the thermal environment during the daytime in summer.