• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.156-160
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• 2007

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some sonic and subsonic ejectors with the function of changing nozzle position were manufactured precisely and tested for the comparison with the calculation results.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.256-259
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• 2008

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some ejectors with a various of nozzle throat and mixing chamber diameter were manufactured precisely and tested for the comparison with the calculation results.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.261-272
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• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• Journal of ILASS-Korea
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• v.18 no.1
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• pp.35-43
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• 2013

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross flow are reviewed and classified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and column fracture height, respectively. The empirical correlations for the prediction of column fracture distance can be classified as constant form, momentum flux ratio form, Weber number form and other parameter form, respectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio form, Weber number form and other parameter form, respectively. It can be summarized that the breakup length of liquid jet in a cross flow is a basically function of the liquid to air momentum flux ratio. However, Weber number, liquid-to-air viscosity ratio and density ratio, Reynolds number or Ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrepancies of predicted values by the existing correlations even though many correlations have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location etc. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.38-45
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• 2015

In this study, two computational methodologies were compared to consider an effective conjugate heat transfer analysis technique for the cooled vane with thermal barrier coating. The first one is the physical modeling method of the TBC layer on the vane surface, which means solid volume of the TBC on the vane surface. The second one is the numerical modeling method of the TBC layer by putting the heat resistance interface condition on the surface between the fluid and solid domains, which means no physical layer on the vane surface. For those two methodologies, conjugate heat transfer analyses were conducted for the cooled vane with TBC layer having various thickness from 0.1 mm to 0.3 mm. Static pressure distributions for two cases show quite similar patterns in the overall region while the physical modeling shows quite a little difference around the throat area. Thermal analyses indicated that the metal temperature distributions are quite similar for both methods. The results show that the numerical modeling method can reduce the computational resources significantly and is quite suitable method to evaluate the overall performance of TBC even though it does not reflect the exact geometry and flow field characteristics on the vane surface.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.281-285
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• 2007

The flow characteristics in the thruster should be analyzed considering its geometry and the pressure ratio to estimate its performance and etc. This paper suggests the computational result of an axisymmetric real nozzle for the altitude control of a satellite to find out the application limit that the assumption of continuum mechanics holds. The steady non-reacted compressible flow field in the unstructured grid system is computed and analyzed with varying the environmental pressure (or the degree of vacuum) under the fixed pressure ratio in a real thruster of which the area ratio of exit to throat is 56. The assumption of the continuum mechanics is not approved when the environmental pressure is reduced less than $10^{-3}$ atm.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.821-830
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction steam line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical results using the FLUENT code and the down scale experimental data on effect of geometry of the impingement baffle plate on the shell wall thinning. Additionally, a new type impingement baffle plate was installed above the impingement baffle plate in the feedwater heater and then the numerical and experimental study were performed in the same progress.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.26-33
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• 2001

Thrust vector control system is control device which is mounted exit of the nozzle to generate pitch, yaw and roll directional force by deflecting flow direction of the supersonic jet from the nozzle. By obtaining control force, jetvane which is exposed in jet flow is working thermal and aerodynamic load. Axial thrust loss and side thrust is affected by shock patterns and interactions between jetvanes according to jetvane geometry and turning angle. In this study, we designed 6 types of jetvane to evaluate pitch, yaw and roll characteristics of ietvane in supersonic flow, and perform the cold flow test in range of turning angles of jetvanes between $0^{\cire}$ and $25^{\cire}$ by $5^{\cire}$ respectively. Also, calculation is going side by side to analyse flow interaction. Results show that there is no interactions between jetvanes upto turning angle 20$^{\circ}$, chord and lead length ratio is very important parameter to aerodynamic performance and maximum thrust loss is appeard to 17% of axial thrust in roll directional control.

• Textile Coloration and Finishing
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• v.34 no.2
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• pp.109-116
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• 2022

Tire codes are made of materials such as hemp, cotton, rayon, nylon, steel, polyester, glass, and aramid are fiber reinforcement materials that go inside rubber to increase durability, driveability, and stability of vehicle tires. The reinforcement of the tire cord may construct a composite material using tires such as automobiles, trucks, aircraft, bicycles, and fibrous materials such as electric belts and hoses as reinforcement materials. Therefore, it is essential to ensure that the adhesive force between the rubber and the reinforced fiber exhibits the desired physical properties in the rubber composite material made of a rubber matrix with reinforced fibers. This study is a study on the heat treatment conditions for improving the adhesion strength of the tire cord and the reinforced fiber for tires. The core technology of the drying process is a uniform drying technology, which has a great influence on the quality of the reinforcement. Therefore, the uniform airflow distribution is determined by the geometry and operating conditions of the dryer. Therefore, this study carried out a numerical analysis of the shape of a drying nozzle for improving the performance of hot air drying in a dryer used for drying the coated reinforced fibers. In addition, the flow characteristics were examined through numerical analysis of the study on the change in the shape of the chamber affecting drying.

• Fire Science and Engineering
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• v.30 no.6
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• pp.111-117
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• 2016

The present study examined the free surface flow of a liquid sheet near a sprinkler head using a Computational Fluid Dynamics (CFD) model and considered the feasibility of the empirical model for predicting the initial spray characteristics of the sprinkler head through a comparison of the CFD results. The CFD calculation for a simplified sprinkler geometry considering the nozzle and deflector were performed using the commercially available CFD package, CFX 14.0 with the standard $k-{\varepsilon}$ turbulence model and theVolume of Fluid (VOF) method. The predicted velocity of the empirical model at the edge of deflector were in good agreement with that of the CFD model for the flat plate region but there was a certain discrepancy between the two models for the complex geometry region. The mean droplet diameter predicted by the empirical model differed significantly from the measured value of the real sprinkler head. On the other hand, the empirical model can be used to understand the mechanism of droplet formation near the sprinkler head and predict the initial spray characteristics for cases without experimental data.