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Schlieren 기법과 수치해석을 이용한 저압 상황의 초음속 제트 유동 연구
지윤영(Yun Young Ji),장동규(Dong Kyu Jang),손동기(Dong Kee Sohn),고한서(Han Seo Ko) 한국가시화정보학회 2020 한국가시화정보학회지 Vol.18 No.2
Research on shock structures of supersonic jet through visualization experiments in low-pressure environment have not been actively conducted. Therefore, in this study, shock waves and supersonic jets were analyzed and compared by numerical analysis and Schlieren technique at low-pressure. Schlieren technique is commonly used to visualize the shock waves generated by density gradient as interferometric methods. Pressure ratio of entrance and ambient was set around 4 to observe moderate under-expanded jet. For validation of experimental and numerical results, the shock structure and frequency were compared. In the case of ST and C nozzle, the results were shown that the difference of shock cell distance was within 10%. The Mach number gradually decreased due to energy reduction, and the error rate was within 7%. D nozzle was not fitted to be observing the shock structure. Because the interface between rarefaction fan and supersonic jet was ambiguous and oscillating phemenoma occurred at end of jet, the supersonic jet in low ambient pressure was observed and analyzed.
PCM(Phase Change Material)이 적용된 Battery Thermal Management System(BTMS)의 열 분석
지윤영(Yun Young Ji),최성호(Sung Ho Choi),손동기(Dong Kee Sohn),고한서(Han Seo Ko) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Due to electric vehicles, devices and ESS(Energy storage system), the demand for batteries with high-capacity energy is increasing. Batteries that exceed the proper operating temperature have issues such as heat generation, efficiency, lifespan, and thermal runaway. Therefore, research on a battery thermal management system (BTMS) for maintaining an appropriate operating temperature of the battery is important. In this study, we propose a BTMS for keeping a battery temperature with PCM, which is a substance that emits/absorbs latent heat in the isothermal phase change process. To analyze the thermal mechanism, charge/discharge experiments and numerical simulation were performed to confirm the battery temperature distribution and thermal energy.