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65K 과냉 액체질소 생산을 위한 Brayton냉동사이클의 시스템 설계
정명진(M.J. Chung),정원상(W.S. Jung),장호명(H.M. Chang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Bryaton refrigeration cycle is proposed and designed in detail for continuous cooling of liquid nitrogen from 75 K to 65 K at a rate of 5 ㎾. This refrigeration requirement is specified by the superconducting power devices under domestic development, where subcooled liquid nitrogen is used as cooling medium and high-voltage electrical insulator. Helium gas is the refrigerant of Brayton cycle and a plate-fin type of counter-flow heat exchanger is selected for both regenerative heat exchanger and subcooling heat exchanger. With given dimensions of standard plate-fin unit, detailed heat transfer analysis is performed to determine the necessary size of each heat exchanger which will satisfy the refrigeration requirement. It is rigorously shown that there exists a unique optimum in pressure ratio of Brayton cycle to minimize the power input to the refrigerator, when the sum of the two heat exchanger sizes is given as a constant. The practical parameters for selecting the compressor and expander are discussed, and an economic impact of the proposed design is also demonstrated in comparison with commercial G-M or Stirling coolers.
국군 수도병원의 심혈관계 수술 304예에 대한 임상적 고찰
선경,박영환,김범식,이건우,이영욱,백광제,정원상,곽영태,김형묵,Sun, K.,Park, Y.H.,Kim, B.S.,Lee, K.W.,Lee, Y.W.,Baek, K.J.,Jung, W.S.,Kwak, Y.T.,Kim, H.M. 대한흉부심장혈관외과학회 1988 Journal of Chest Surgery (J Chest Surg) Vol.21 No.6
From 1959 through Jun. 1988, 2094 cases of various Cardiovascular diseases were operated, which were consisted of 1215 open heart surgery under extra-corporeal circulation or hypothermia and 879 conventional Cardiovascular Surgery at Department of Thoracic & Cardiovascular Surgery in National Medical Center. There were 1111 congenital heart anomalies and 983 acquired cardiovascular diseases. Among 1111 congenital cases, acyanotic cases were 748 and cyanotic cases were 363. In acquired heart cases, valvular heart diseases [702 cases] were the most frequent and a small No. of cardiac tumor and coronary artery diseases were included. Overall operative mortality was 9.3%, consisting of 4.6% for acyanotic anomaly, 20.6% for cyanotic anomaly and 8.7% for acquired heart diseases. In open heart surgery, overall mortality was 11.6% and 6% in conventional cardiovascular surgery.