• KIEE International Transaction on Systems and Control
• /
• v.2D no.2
• /
• pp.78-91
• /
• 2002

In the thermal power plant, there are six manipulated variables: main steam flow, feedwater flow, fuel flow, air flow, spray flow, and gas recirculation flow. There are five controlled variables: generator output, main steam pressure, main steam temperature, exhaust gas density, and reheater steam temperature. Therefore, the thermal power plant control system is a multinput and output system. In the control system, the main steam temperature is typically regulated by the fuel flow rate and the spray flow rate, and the reheater steam temperature is regulated by the gas recirculation flow rate. However, strict control of the steam temperature must be maintained to avoid thermal stress. Maintaining the steam temperature can be difficult due to heating value variation to the fuel source, time delay changes in the main steam temperature versus changes in fuel flow rate, difficulty of control of the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, and the fluctuation of inner fluid water and steam flow rates during the load-following operation. Up to the present time, the Proportional-Integral-Derivative Controller has been used to operate this system. However, it is very difficult to achieve an optimal PID gain with no experience, since the gain of the PID controller has to be manually tuned by trial and error. This paper focuses on the characteristic comparison of the PID controller and the modified 2-DOF PID Controller (Two-Degrees-Freedom Proportional-Integral-Derivative) on the DCS (Distributed Control System). The method is to design an optimal controller that can be operated on the thermal generating plant in Seoul, Korea. The modified 2-DOF PID controller is designed to enable parameters to fit into the thermal plant during disturbances. To attain an optimal control method, transfer function and operating data from start-up, running, and stop procedures of the thermal plant have been acquired. Through this research, the stable range of a 2-DOF parameter for only this system could be found for the start-up procedure and this parameter could be used for the tuning problem. Also, this paper addressed whether an intelligent tuning method based on immune network algorithms can be used effectively in tuning these controllers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2013.10a
• /
• pp.271-274
• /
• 2013

Considering the recent trend highlighting the importance of STEAM education, the purpose of this study is to develop scientific research activities and STEAM technology material using the smart device sensor. Drawing a picture on a map with GPS drawing application which contains elements such as IT, geographic information, sports and arts, we intent not just to install a smartphone application but also to get synergic effects and help with real cartography and geographic classes which are not experienced in the middle school curriculum, by using the functions of a smart device. Through the development of STEAM teaching material, we intended to provide a clear direction towards advancement by developing creative teaching data and teaching models which encourage students to improve their interest and creativity in science, technology, engineering, art, and mathematics.

• Journal of The Korean Association of Information Education
• /
• v.22 no.3
• /
• pp.325-333
• /
• 2018

This study analyzes students' motivation for learning when applying SW-STEAM education using Flipped Learning. As a main content of the study, we developed a program that combines SW education with existing subjects and utilized flipped learning as a method. Elementary school students were given an education program. The data were collected through pre and post-test of learning motivation. As a result of analysis, the SW-STEAM program based on flipped learning has improved attention, relevance and confidence. We expect that the results of the SW-STEAM education program developed in this study and the learning motivation analysis will help in the direction of the SW-STEAM education and be useful as a basic resources for settling in class.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.156.1-156.1
• /
• 2011

It is of great importance to predict operating parameter characteristics of an integrated fuel processor by the increased life-time and system performance. In this study, computational analysis is performed to gain fundamental insights on transport phenomena and chemical reactions in reformer which consists of preheating, steam reforming, and water gas shift reaction beds. Also, a top-fired burner locates inside of the reforming system. The combustor is providing thermal energy necessary for the steam reforming bed which is a endothermic catalytic reactor. Two-dimensional numerical model of the integrated fuel processing system is introduced for the analysis of heat and mass transport phenomena as well as surface kinetics and catalytic process. A kinetic model was developed and then computational results were compared with the experimental data available in the literature. Subsequently, parameter study using the validated steam methane reforming model was conducted by considering operating parameters, i.e. steam to carbon ratio and temperature.

• Journal of Environmental Science International
• /
• v.25 no.1
• /
• pp.163-171
• /
• 2016

We analyzed the characteristics of fog formation in the Gumi Reservoir of Nakdong river with the field observation data for recent 2 years (1 April 2013~31 March 2015) collected by the national institute of meteorological research, KMA. In early morning, we frequently observe the steam rising from the water surface. The fog occurs from adding water vapor into the air. We call the fog as steam fog. Steam fogs occur when cold, dry air mixes with warm, moist air above a water surface. The steam fog appears mainly in autumn under the following conditions; (1) sensible heat is positive values ($10{\sim}20W/m^2$), (2) latent heat is more positive values ($25{\sim}35W/m^2$) than sensible heat, (3) cloudless nights with light winds (about 1.5 m/s), (4) under condition(3), mountainous winds easily blows into the reservoir.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.7 no.4
• /
• pp.19-25
• /
• 2011

Steam Generator(SG) tube is an important component of Nuclear Power Plant(NPP), which is the pressure boundary between the primary and secondary systems. The integrity of SG tube has been confirmed by the eddy current test every outage. The eddy current technique adopting bobbin probe is currently the primary technique for the steam generator tubing integrity assesment. The bobbin probe is one of the essential components which consist of the whole ECT examination system and provides us a decisive data for the evaluation of tube integrity. Until now, all of the ECT bobbin probes in Korea which is necessary to carry out inspection are imported from overseas. However, KHNP has recently developed the bobbin probe design technology and transferred it to domestic manufacturers to fabricate the probes. This study has been conducted to establish technical requirements applicable to the steam generator tube inspection using the bobbin probes fabricated by the domestic manufactures. The results have been compared with the results obtained by using foreign probe to identify the availability to the steam generator tube inspection. As a result, it is confirmed that the domestic bobbin probe is generally applicable to SG tube inspection in the NPPs.

• Journal of Science Education
• /
• v.37 no.2
• /
• pp.359-373
• /
• 2013

This study is aimed to find out the effect after the development and application of the STEAM teaching-learning program for science gifted elementary school students. The validity of the developed program was verified by three experts. The program consists of a total of eight classes and eight days were carried out. Recorded lessons, class observation journal, and recorded interview transcription data were measured and then analyzed the effect. 'Present situation' is a very important step was confirmed. The degree of understanding of a given situation affected to task commitment, the formation of scientific concepts, creative design and deliverable.

• Journal of the Korea Society of Computer and Information
• /
• v.21 no.6
• /
• pp.29-37
• /
• 2016

In this paper, we evaluated educational effects of H-STEAM group play contents(a course) and tried to suggest a convergent model for college liberal art curriculum. We opened a mixed course(math, art, engineering, and humanities) with team teaching for this purpose. For the test, we collected data from survey, K-W-L sheet, and reflection paper from 23 students who enrolled in this course. Students should do a team project during the course, propose a new group game, and write K-W-L sheet at the end of each session and reflection paper at the final stage. As a result, it is said that H-STEAM group contents had an effect on students' satisfaction and achievement. During the course, students made academic efforts and were able to construct convergent knowledge from the four fields. From this study, we are sure that H-STEAM contents can play a substitute role for the traditional liberal arts program and innovate the curriculum for the knowledge convergence society.

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

• Nuclear Engineering and Technology
• /
• v.45 no.3
• /
• pp.347-360
• /
• 2013

This paper presents an experimental investigation of the small-break loss-of-coolant accident (SBLOCA) and the loss-of-feedwater accident (LOFW) in a scaled integral test facility of REX-10. REX-10 is a small integral-type PWR in which the coolant flow is driven by natural circulation, and the RCS is pressurized by the steam-gas pressurizer. The postulated accidents of REX-10 include the system depressurization initiated by the break of a nitrogen injection line connected to the steam-gas pressurizer and the complete loss of normal feedwater flow by the malfunction of control systems. The integral effect tests on SBLOCA and LOFW are conducted at the REX-10 Test Facility (RTF), a full-height full-pressure facility with reduced power by 1/50. The SBLOCA experiment is initiated by opening a flow passage out of the pressurizer vessel, and the LOFW experiment begins with the termination of the feedwater supply into the helical-coil steam generator. The experimental results reveal that the RTF can assure sufficient cooldown capability with the simulated PRHRS flow during these DBAs. In particular, the RTF exhibits faster pressurization during the LOFW test when employing the steam-gas pressurizer than the steam pressurizer. This experimental study can provide unique data to validate the thermal-hydraulic analysis code for REX-10.