• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.987-995
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• 2019

Steam jet condensation is of great importance to pressure suppression containment and automatic depressurization system in nuclear power plant. In this paper, the condensation processes of sonic steam jet in a quiescent subcooled pool are recorded and analyzed, more precise understanding are got in direct contact condensation. Experiments are conducted at atmospheric pressure, and the steam is injected into the subcooled water pool through a vertical nozzle with the inner diameter of 10 mm, water temperature in the range of $25-60^{\circ}C$ and mass velocity in the range of $320-1080kg/m^2s$. Richardson number is calculated based on the conservation of momentum for single water jet and its values are in the range of 0.16-2.67. There is no thermal stratification observed in the water pool. Four condensation regimes are observed, including condensation oscillation, contraction, expansion-contraction and double expansion-contraction shapes. A condensation regime map is present based on steam mass velocity and water temperature. The dimensionless steam plume length increase with the increase of steam mass velocity and water temperature, and its values are in the range of 1.4-9.0. Condensation heat transfer coefficient decreases with the increase of steam mass velocity and water temperature, and its values are in the range of $1.44-3.65MW/m^2^{\circ}C$. New more accurate semi-empirical correlations for prediction of the dimensionless steam plume length and condensation heat transfer coefficient are proposed respectively. The discrepancy of predicted plume length is within ${\pm}10%$ for present experimental results and ${\pm}25%$ for previous researchers. The discrepancy of predicted condensation heat transfer coefficient is with ${\pm}12%$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.669-675
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• 2015

In this study, we investigate the performance variations of an automotive turbocharger compressor with respect to the height variation of the recirculating casing treatment (RCT). We use three RCT heights, namely 1.2 mm, 1.5 mm, and 1.8 mm. We vary the compressor speed from 90,000 to 150,000 rpm, and the flow rate from 0.015 kg/s to 0.08 kg/s. The calculation results of the total pressure ratio and isentropic efficiency showed good agreement with the performance data provided by the manufacturer within a 0.7 percent error. The results showed that the RCT heights of 1.2 mm, 1.8 mm, and 1.5 mm, in that order, exhibited a more uniform pressure distribution, higher pressure ratio, and wider operational range. As the number of revolutions per minute increased, we obtained typical characteristics of a compressor map having a narrower operational range in the region of higher pressure ratio.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.74-79
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• 2012

The present study aims at suggesting the systematic approach to analyze the local drag components as the resistance performance characterized by the flow of the ship. In order to identify the local areas, the hull surface is decomposed into SVM (Station-Vertical Section Map) which consists of 20 stations along the longitudinal direction and 20 sections along the vertical direction (from the bottom to the waterline). Successively, on the SVM, the friction and pressure drag coefficients as the components of total drag coefficient have been analyzed for two different hull forms of Wigley and KVLCC by using CFD.

• Nuclear Engineering and Technology
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• v.29 no.1
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• pp.45-57
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• 1997

The direct contact condensation phenomenon, which occurs when steam is injected into the subcooled water, has been experimentally investigated. Two plume shapes in the stable condensation regime are found to be conical and ellipsoidal shapes depending on the steam mass flux and the liquid subcooling. Divergent plumes, however, are found when the subcooling is relatively small. The measured expansion ratio of the maximum plume diameter to the injector inner diameter ranges from 1.0 to 2.3. By means of fitting a large amount of measured data, an empirical correlation is obtained to predict the steam plume length as a function of a dimensionless steam mass flux and a driving potential for the condensation process. The average heat transfer coefficient of direct contact condensation has been found to be in the range 1.0~3.5 ㎿/$m^2$.$^{\circ}C$. Present results show that the magnitude of the average condensation heat transfer coefficient depends mainly on the steam mass fin By using dynamic pressure measurements and visual observations, six regimes of direct contact condensation have been identified on a condensation regime map, which are chugging, transition region from chugging to condensation oscillation, condensation oscillation, bubbling condensation oscillation, stable condensation, and interfacial oscillation condensation. The regime boundaries are quite clearly distinguishable except the boundaries of bubbling condensation oscillation and interfacial oscillation condensation.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.353-362
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• 2016

Thermal barrier coating (TBC) is an essential element consisting of a super-alloy base and ceramic coating designed to achieve long operational time under a high temperature and pressure environment. However, the top coat of TBC can be delaminated at certain temperatures with long operation time. As the delamination of TBC is directly related to the blade damage, the coupling status of the TBC should be assured for reliable operation. Conventional studies of nondestructive evaluation have been made for detecting generation of thermally grown oxide (TGO) or qualitatively evaluating delamination in TBC. In this study, the ultrasonic C-scan method was developed to obtain the damage map inside TBC by estimating the delamination in a quantitative way. All specimens were isothermally degraded at $1,100^{\circ}C$ with different time, having different partial delamination area. To detect partial delamination in TBC, the C-scan was performed by a single transducer using pulse-echo method with normal incidence. Partial delamination coefficients of 1 mm to 6 mm were derived by the proportion of the surface reflection signal and flaw signal which were theoretical signals using Rogers-Van Buren and Kim's equations. Using the partial delamination coefficients, the partial delamination maps were obtained. Regardless of the partial delamination coefficient, partial delamination area was increased when degradation time was increased in TBC. In addition, a decrease in partial delamination area in each TBC specimen was observed when the partial delamination coefficient was increased. From the portion of the partial delamination maps, the criterion for delamination was derived.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.214-219
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• 2003

This paper includes real-time tractive force estimation method using standard vehicle sensors such as wheel speed, brake pressure, throttle position, engine speed, and transmission carrier speed sensor. Engine map, torque converter lookup table, shaft torque observer, and brake gain adaptation method are used to estimate the tractive force. To verify this estimator, measurement which uses strain-based brake torque sensor and estimation results are presented. All results was performed using a real vehicle in a real-time.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.51-59
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• 2018

Health care has attracted a lot of attention, recently due to an increase in life expectancy and interest in health. Various biometric data of the user are collected by using the air pressure sensor, gyro sensor, acceleration sensor, and heart rate sensor to perform the Smart Health Care Activity Tracker function. Basically, smartphone application is made and tested for biometric data collection, but the Arduino platform and bio-signal measurement sensor are used to confirm the accuracy of the measured value of the smartphone. Use the Google Maps API to set user goals and provide guidance on the location of the user and the points the user wants. Also, the basic configuration of the main UI is composed of the screen of the camera, and it is possible for the user to confirm the forward while using the application, so that accident prevention is possible.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.6
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• pp.545-554
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• 1998

The diurnal variation of O3 concentration shows two peaks, the first peak at noontime and the secondary peak at night. In order to show why the secondary peak, high nocturnal O3 concentration, occurs without sunlight which is a essential factor of a photochemical response, the O3 concentration, several weather elements and synoptic weather map were used for June∼September at 1995, 1996. The mean concentration of high nocturnal O3 concentration days is higher by 5.4 ppb than that of low nocturnal O3 concentration days. The nocturnal O3 concentration is higher than that of diurnal O3 concentration during high nocturnal O3 concentration days, at July, 1995 and June, 1996. The high nocturnal O3 concentration is related to low air pressure, high cloud cover and high wind speed. The correlation coefficient, r. between nocturnal O3 concentration and wind speed, pressure and cloud cover is 0.387, -0.218, and 0.194, respeftiviely. It is interesting that the O3 concentration increases at Pusan when the typhoon passes by. The same result showed at Taegu when the typhoon FAYE passed by. According to the analysis of nocturnal O3 concentration for June∼September at 1995 and 1996, it seems that the high nocturnal O3 concentration relates to the trough and cyclones passing by Pusan.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.1-7
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• 2013

An aerodynamic rig test of a radial turbine for an auxiliary power unit (APU) was performed at a high-temperature turbine test facility at the Korea Aerospace Research Institute. The pressure ratio, Mach number, and flow coefficient in the rig test are the same as those under normal engine operation conditions. The design pressure ratio is 3.096, design test speed is 34909 rpm, and turbine inlet temperature is $160^{\circ}C$. The turbine has airfoil-type nozzles, and the diameter of the turbine wheel is 175.74 mm. The turbine map is experimentally measured, and the detailed flow at the turbine inlet is measured. The pressure distribution in the nozzle at both the hub and the shroud sides and the pressure distribution along the shroud casing of the turbine wheel were measured, and this confirmed that the expansion process in the turbine wheel is acceptable.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.74-83
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• 2003

In the advanced nuclear power plants including APR1400, the SDVS (Safety Depressurization and Vent System) is adopted to increase the plant safety using the concept of feed-and-bleed operation. In the case of the TLOFW (Total Loss of Feedwater), the POSRV (Power Operated Safety Relief Value) located at the top of the pressurizer is expected to open due to the pressurization of the reactor coolant system and discharges steam and/or water mixture into the water pool, where the mixture is condensed. During the condensation of the mixture, thermal-hydraulic loads such as pressure and temperature variations are induced to the pool structure. For the pool structure design, such thermal-hydraulic aspects should be considered. Understanding the phenomena of the submerged steam jet condensation in a water pool is helpful for system designers to design proper pool structure, sparger, and supports etc. This paper reviews and evaluates the steam jet condensation in a water pool on the physical phenomena of the steam condensation including condensation regime map, heat transfer coefficient, steam plume, steam jet condensation load, and steam jet induced flow.