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Chiller용 냉매 CFC-11과 대체냉매 HCFC-123의 전기장을 사용한 핵비등 열전달 촉진에 관한 연구
곽태희,김주형,정동수,김종보,차태우,한창섭,Kwak, T.H.,Kim, J.H.,Jung, D.S.,Kim, C.B.,Cha, T.W.,Han, C.S. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.4
Pool boiling experiments were carried out to study the effect of electric field on nucleate boiling heat transfer. CFC-11 and its alternative HCFC-123 were used as working fluids. Boiling on both single tube and a bundle of five tubes was investigated. Heat flux varied from 5 to $25kW/m^2$ while the applied voltage changed from 0 to 1kV. The results showed that at low heat flux where boiling was not present or very weak, electric field-induced forced convection helped increase the heat transfer coefficients of CFC-11 and HCFC-123 significantly(4-15 times increase). However, at higher heat flux, nucleate boiling of CFC-11 which is a highly dielectric fluid, was not affected significantly by the application of electric field. In contrast to CFC-11, even at high heat flux, nucleate boiling of CFC-11 which has a relatively larger electric conductivity than CFC-11, was vigorously increased up to 2-4 times. The additional power required to apply the electric field was 1-2% of the total power consumption by the heater. The increase in overall heat transfer coefficient of evaporators with HCFC -123 was about 40%, suggesting a considerable reduction in evaporator size with EHD technique.
곽태희(Taehee Kwak),임정하(JungHa Lim) 한국아동학회 2019 아동학회지 Vol.40 No.2
Objectives: The purpose of this study was to investigate the relationship between emotional awareness and psychological well-being in adolescents with cognitive emotion regulation strategies as mediators. Methods: A total of 375 middle and high school students in Seoul and Gyeonggi-do participated. Self-report questionnaires were used to assess their emotional awareness, adaptive and maladaptive emotion regulation strategies, and psychological well-being. The data were analyzed using descriptive statistics, Pearson’s correlations, and regression analyses in PROCESS macro. Results: First, emotional awareness was related to both cognitive emotion regulation strategies and psychological well-being. Also, adaptive strategies for regulating emotions were strongly related to psychological well-being, while maladaptive strategies were inversely related to psychological wellbeing. Second, both adaptive and maladaptive emotion regulation strategies partially mediated the link between emotional awareness and psychological well-being in adolescents. Conclusions: These findings indicate that emotional awareness and cognitive emotion regulation strategies are important factors in improving the psychological well-being of adolescents.
임정하(Lim, JungHa),송지은(Song, Jieun),곽태희(Kwak, Taehee),백지민(Baek, Jimin),권오연(Kwon, Ohyeon) 한국청소년정책연구원 2017 한국청소년연구 Vol.28 No.3
본 연구는 남녀 청소년의 완벽주의와 사회불안 간의 관계에서 자기수용의 매개효과를 검증하고자 수행되었다. 이를 위하여 서울과 경기에 소재한 6개 중․고등학교에 재학 중인 청소년 386명을 대상으로 자기보고식 설문조사를 실시하였다. 수집된 자료는 t 검증, Pearson의 적률상관분석, 구조방정식모형, 다집단 분석을 이용하여 분석하였다. 주요 연구결과는 다음과 같다. 첫째, 자기지향 완벽주의는 성별에 따라 유의한 차이가 있었는데, 여자 청소년들이 남자 청소년들보다 스스로의 행동에 완벽한 기준을 설정하고 엄격한 판단을 하는 것으로 나타났다. 사회부과 완벽주의와 자기수용 및 사회불안에서는 성별에 따른 유의한 차이가 나타나지 않았다. 둘째, 자기수용과 사회불안 간의 관계가 완벽주의와 사회불안 간의 관계보다 관련성이 더 강한 것으로 나타났고, 자기수용은 사회부과 완벽주의와 사회불안 간의 관계를 완전매개하였다. 즉 타인이 자신에게 완벽함을 요구한다고 생각할수록 자신을 있는 그대로 수용하기 어려우며, 이는 청소년의 사회불안을 높이는 것으로 나타났다. 셋째, 성별에 따라 자기수용의 매개경로는 다르게 나타났다. 남자 청소년 집단에서는 자기수용이 자기지향 완벽주의와 사회불안 간의 관계, 사회부과 완벽주의와 사회불안 간의 관계를 매개하였다. 여자 청소년 집단에서는 자기수용이 사회부과 완벽주의와 사회불안 간의 관계에서만 매개효과를 보였다. 이러한 연구결과는 남녀 청소년들의 사회불안을 완화하기 위한 프로그램 개발 및 상담에 기초 자료로 활용될 수 있을 것이다. The purpose of this study was to investigate the mediating effects of self-acceptance in the relationship between perfectionism and social anxiety amongst adolescents. A total of 386 middle and high school students in Seoul and Gyeonggi area participated in the study. The data were analyzed using t-tests, Pearson’s correlations, structural equation modeling and multi-group analysis. The results were as follows. First, adolescent girls reported higher levels of SOP(self oriented perfectionism) than adolescent boys. The levels of SPP(socially prescribed perfectionism), self-acceptance and social anxiety were not significantly different as a function of gender. Second, there was a full mediating effect of self-acceptance in the relationship between SPP and social anxiety. Third, the relationship between SPP and social anxiety was fully mediated by self-acceptance in both adolescent boys and girls, whereas the relationship between SOP and social anxiety was fully mediated by self-acceptance only in adolescent boys. These results suggest that self-acceptance needs to be considered as a means of decreasing social anxiety when designing programs and counselling for adolescents.
하이브리드 자동차용 모터 내부의 오일 냉각 시스템에 대한 수치해석
김종수(J.S. Kim),문정욱(J.W. Moon),곽태희(T.H. Kwak),강태곤(T.G. Kang) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.3
This paper presents the numerical study on the flow and heat transfer in an oil cooling system for the motor employed in a hybrid vehicle. The heat sources in the motor are identified by conducting numerical simulations for the electromagnetic field. Then, they are used as input parameters in the thermal analysis. The multiple reference frame(MRF) scheme in a commercial software, ANSYS CFX, is used to treat the rotating rotor. A separated flow model is employed to solve the non-isothermal two-phase flow of the oil-air mixture. We mainly focus on the influence of the oil injection and the fluid flow caused by rotating parts on the performance of the oil cooling system. At two typical operating points of the motor, it is found that the temperature distribution in the motor is highly affected by the injection rate of the oil. In addition, the convective heat transfer caused by the secondary flows occurring in the gap between the stator and rotor also contribute to cooling.
공조용 열교환기 튜브-튜브시트 조인트의 신뢰성 평가를 위한 실험 및 해석에 관한 연구
박진성(Jin-Seong Park),박내현(Nae-Hyun Park),곽태희(Tae-Hee Kwak),조종래(Jong-Rae Cho) 한국기계가공학회 2024 한국기계가공학회지 Vol.23 No.5
Shell-and-tube heat exchangers are extensively used in diverse industrial sectors. However, they are exposed to high-temperature and high-pressure fluids, and the tube-tubesheet joint emerges as a critical failure point. The roller expansion process for groove joint assembly is advantageous in terms of manufacturing, workability, and cost-effectiveness. Here, we assessed the pullout strength and residual compressive pressure of these joints via experimental and numerical analyses. Additionally, we confirmed the joint tightness after expansion and proposed a methodology for evaluating the joint integrity under real heat exchanger operating conditions. This study aims to evaluate the integrity of tube-tubesheet joints for shell-and-tube heat exchanger designs to ensure integrity against failures and uphold long-term reliability.