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Parallel-expander Organic Rankine cycle using dual expanders with different capacities
Yun, E.,Kim, D.,Lee, M.,Baek, S.,Yoon, S.Y.,Kim, K.C. Pergamon Press 2016 ENERGY Vol.113 No.-
This study reports on a parallel-expander Organic Rankine cycle (PE-ORC) using dual expanders with different capacities. This system is applicable to waste heat sources that have large variation, such as distributed power plants with varying electricity demand. The test bench for the experimental investigation consists of a PE-ORC loop with two different scroll expanders, an electrical water heating system, and an air-cooled chiller. The tested performance characteristics for each operating mode are presented. The experimental results show three clearly separated operation regions with high efficiency, two possible switching points of the operating mode, and good heat recovery capability over a wider range of heat input compared to a PE-ORC system with two identical expanders. A control strategy for the system is proposed to maintain superheated state at the inlet of expander and to obtain high performance after changing the operating mode.
박윤배 慶北大學校 師範大學 科學敎育硏究所 1998 科學敎育硏究誌 Vol.22 No.-
This study surveyed the secondary science teachers' needs on inservice program for certification. Data were collected by using a questionnaire developed by this author from 90 teachers attended the summer inservice program. The teachers wanted that the inservice program covered more in science experiment area and less in liberal arts, pedagogy, and science theory areas. As the content of science area, they wanted science education content necessary for secondary school practice. The teachers' satisfaction rate was around 3 of 5-point scale. They preferred presentation and lecture as instruction method of the program. Some practical suggestions were made.
박윤배,전태식,강애남 慶北大擧校 師範大學 科學敎育硏究所 2000 科學敎育硏究誌 Vol.24 No.-
We investigated the effective instructional methods of levelized curriculum in secondary school science. A total of 923 students from grade 7 to 10 and 5 teachers were involved in this study. Questionnaire for students' need and perceptions toward the levelized instruction, questionnaire for teachers' perception, and instructional material were developed and administered. Results showed students wanted various methods and topics related with daily living. Difficulty is the primary reason why the students lost their interest toward science subject. The same kind of activities, although dealing with different contents, were recommended for both enrichment and complement groups. Group dynamics techniques and process evaluation were needed for getting higher effect. Teachers expressed the levelized instruction was more difficult than traditional instruction in terms of preparation, delivery, and evaluation. Although there was no significant gain at the levelized group in comparision with traditional group, interest and involvement level were raised significantly.
박윤배,박윤선 慶北大學校 師範大學 科學敎育硏究所 1999 科學敎育硏究誌 Vol.23 No.-
The purpose of this study was to examine the effect of analogy instruction for correcting middle school students' misconceptions on electric current. A total of 23 subjects ranged from 7 to 9 grade were sampled as volunteer from an urban area middle school. Two group pretest-posttest design was used. A formative test was also administered to check the subjects' understanding about the treatment instruction. An automatic doll analogy was developed for this study. As result, the analogy instruction was effective for correcting most misconceptions on electric current, especially SF(sequential flow) idea, RI(resistance irrelevant) idea, and DP(current at direct circuit greater than at pararrel circuit) idea.
박윤배,김차식 慶北大學校 科學敎育硏究所 2003 科學敎育硏究誌 Vol.27 No.-
The purpose of this study was to identify the possibility of use of mind map in vocational high school science class. Eleventh graders in a vocational high school in Daegu were our subject. Topics for making mind map were digestion, nerve system, reproduction, and genetics. A criteria for mind map evaluation and several mind maps were presented. The students were very liked the use of mind map and it might be a very effective instructional technique for vocational high school.