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극저온 맥동 압력 조건에서의 재생기에 관한 실험적 연구
남관우,정상권,정은수,Nam, Gwan-U,Jeong, Sang-Gwon,Jeong, Eun-Su 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.8
An experimental apparatus was prepared to investigate thermal and hydrodynamic characteristics of regenerator at cryogenic temperature under pulsating pressure condition. The regenerator was pressurized and depressurized by a compressor with various operating frequencies. Cold end of the regenerator was maintained around 100 K by means of a liquid nitrogen heat exchanger. Instantaneous gas temperature and mass flow rate were measured at both ends of the regenerator during the whole pressure cycle. Pulsating pressure drop across the regenerator was also measured to see if it could be predicted by a friction factor at steady flow condition. The operating frequency of pressure cycle was varied between 3 and 60 Hz, which are typical operating frequencies of Gifford-McMahon, pulse tube, and Stilting cryocoolers. First, the measured friction factor for typical wire screen mesh regenerator was nearly same as steady flow friction factor for maximum oscillating Reynolds number up to 100 at less than 9 Hz. For 60 Hz operations, however, the discrepancy between oscillating flow friction factor and steady flow one was noticeable if Reynolds number was higher than 50. Second, the ineffectiveness of regenerator was directly calculated from experimental data when the cold-end was maintained around 100 K and the warm-end around 293 K, which simulates an actual operating condition of cryogenic regenerator. Influence of the operating frequency on ineffectiveness was discussed at low frequency range.
남관우,정상권,정은수 대한설비공학회 2000 설비공학 논문집 Vol.12 No.3
A basic pulse tube refrigerator has been constructed with extensive instrumentation to study the characteristics of the heat exchanger experimentally under the oscillating pressure and the oscillating flow. This paper describes the sequential experiments with the basic pulse tube refrigerator. The experiments were performed for various cycle frequencies under the square pressure wave forms. First, the heat flux was measured through the cycle at the both cold and warm end heat exchangers without the regenerator. In order to enhance the thermal communication capability of the heat exchanger with the gas at low operating frequencies, a unique design of the triangular shape radial fin concept was applied to the heat exchangers. For the fin heat exchanger, the measured heat flux and the calculated heat flux from the two well-known oscillating heat transfer correlations were compared and discussed. Second, the regenerator was added to the pulse tube to make a basic pulse tube refrigerator configuration. The experiment showed the great impact of the regenerator on the temperature and the heat flux profiles. At the warm-end, the cyclic averaged heat flux had its maximum value at the specific operating frequency. The paper presents the explanation of the surface heat pumping effect as well as the experimental data.
간동맥 화학색전술 후 발생한 Lipiodol에 의한 총담관 내 이물 1예
남관우,권대순,문희석,김석현,이병석,이헌영,성재규,정현용 대한소화기내시경학회 2008 Clinical Endoscopy Vol.37 No.2
총담관 내 이물은 흔히 경험하기가 어려우며, 몇몇 증례보고들을 종합하여 분석하여 보면, 수술이나 외상과 같은 외적 요인에 의한 경우가 대부분이고, 드물게는 담도계의 구조적 문제로 인하여 음식물이 역행하여서 발생하기도 한다. 간동맥 화학색전술은 간세포암이나 전이된 간암에서의 치료법으로 특히 수술적 치료가 어려운 경우에 널리 이용되고 있다. 악성 부신피질종양의 단일 간 내 전이 병변에 대해서 간동맥 화학색전술을 하고 47일이 경과된 후에 발생한 총담관 내 담석과 같은 증상을 보인 1예가 있어서 문헌고찰과 함께 보고한다. 유두부괄약근 절개술을 시행후 성공적으로 이물을 제거하였으며, 이것은 어두운 흑색의 말랑말랑하고 부드러운 성질이었다. 이것은 리피오돌(Lipiodol)을 포함하는 조직이 떨어져나와 이물을 형성한 것으로 판단된다.