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- 저자 : 전민주(Min-Joo Jeon) (검색결과 4 건)
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내부 열교환기를 이용한 R744용 초임계 냉동사이클의 성능분석
최경민(Kyoung-Min Choi),전민주(Min-Joo Jeon),손창효(Chang-Hyo Son),오후규(Hoo-Kyu Oh) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
This paper considers the influence of internal heat exchangers to the efficiency of a refrigerating system. These internal Heat exchangers (liquid-suction or suction-line heat exchangers) can, in some cases, yield improved system performance while in other cases they degrade system performance. A steady state mathematical model is used to analysis the performance characteristics of refrigeration system with internal Heat exchanger. The influence of operating conditions, such as gas cooler pressure and evaporation temperatures, superheat in the evaporator and temperature of gas cooler outlet, to optimal dimensions of the heat exchanger is also analyzed in the paper. The main results were summarized as follows : the mass flowrate of R744, inner diameter tube and length of internal heat exchanger, and effectiveness have an effect on the cooling capacity, compressor work and RCI(Relative capacity index) of this system. With a thorough grasp of these effect, it is necessary to design the R744 compression refrigeration cycle using internal heat exchanger.
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NH₃-CO₂용 캐스케이드 냉동시스템의 최대 성능 예측
이대훈(Dae-Hun Lee),전민주(Min-Joo Jeon),손창효(Chang-Hyo Son),오후규(Hoo-Kyu Oh) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In this paper, cycle performance analysis of NH₃-CO₂(R717-R744) cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree and condensing and evaporating temperature in the ammonia(R717) high temperature cycle and the carbon dioxide low temperature cycle. The main results were summarized as follows : The COP of cascade refrigeration system increases with the increasing superheating degree, but decreases with the increasing subcooling degree. The COP of cascade refrigeration system increases with the increasing condensing temperature, but decreases with the increasing evaporating temperature. Therefore, superheating and subcoolng degree, compressor efficiency, and evaporating and condensing temperature of NH₃-CO₂(R717-R744) cascade refrigeration system have an effect on the COP of this system. A multilinear regression analysis was employed in terms of subcooling, superheating, evaporating, condensing, and cascade heat exchanger temperature difference in order to develop mathematical expressions for maximum COP and an optimum evaporating temperature.
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곽창수 ( Chang Su Kwak ),이충일 ( Chung Il Lee ),양정수 ( Jung Soo Yang ),전민주 ( Min Joo Jeon ),목승한 ( Seung Han Mok ) 한국스포츠정책과학원(구 한국스포츠개발원) 2007 체육과학연구 Vol.18 No.2
본 연구는 신발 착화 시 편안함과 관련된 요인들을 규명하는데 그 목적이 있다. 본 연구의 피험자는 남자 대학생 30명이었으며, 22가지 신발조건에 대한 인지도검사를 실시하여 상위 10가지 조건에 대한 각 관련변인을 분석하였다. 연구결과 가장 좋은 착화감을 나타낸 신발은 중저의 경도가 전족 50도, 후족 50도이고, 인솔은 높은 아치, 라스트 둘레는 현재 많이 사용되고 있는 기준 라스트, 힐 카운터 심두께는 2mm인 경우였다. 두 가지 속도 조건에서 고관절 회외 모멘트와 무릎관절 회외 모멘트는 작게 나타났고, 최대 후족각의 변화량은 7-11도, 최대 아킬레스건각의 변화량은 10-13도를 나타냈으며, 착화감 순위사이에는 별다른 경향을 나타내지 않았다. 본 연구결과를 고려한 일반 운동화를 설계할 때 전족의 경도를 50이하로 하면 고관절, 무릎, 발목관절의 회외 모멘트가 크게 나타나므로 전족경도는 50이하로 설계하는 것은 바람직하지 않을 것으로 사료된다. 또한 몸무게 70kg 이하 시 중저의 경도 40 이상일 경우 bottom up 현상이 일어나지 않을 수 있으며, 특히, 50kg 이상일 경우 bottom up 현상이 일어나지 않을 것으로 판단되어 1등 조건에서의 경도는 신발설계에 활용될 수 있을 것으로 판단된다. 본 연구결과 중저의 경도가 작을 때 무릎관절과 발목관절의 회외모멘트가 작게 나타났다. 이는 선행연구의 후족부위의 중저의 경도가 작을수록 회외운동이 크게 나타난다는 연구결과와 상반되는 것으로 이를 검증하기 위한 추후연구가 필요하다고 생각된다. Korean shoes industry has been playing a substantial role in Korean economy, however the issue of lack of international competitiveness was raised and discussed in spite of its great potential. The primary reason for this is thought to be the lack of know-how on comfort footwear. Therefore, the purpose of this study was to find out the factors on comfort so that the Korean shoes industry can enhance and develop the new developing technology using the results of this study. Subjects in this study were 30 male university students with normal foot and no injury in lower extremity. Total of 22 shoe conditions were tested on shoe comfort and top 10 factors were analyzed using cinematography and ground reaction force measurement. Results of this study were as followings. 1. The best shoes in comfort cognition test had forefoot region 50 degree, rear-foot region 50 degree in mid-sole hardness, high arch in insole, standard last, and 2mm hill counter thickness. 2. Comfort was best when forefoot region thickness was in standard last level and hill-counter thickness was 2mm. 3. High and standard arch created comfort. Therefore, this factor should be considered when designing shoes or insole. 4. In two speed condition, pronation moment in hip joint and knee joint was decreased and they had little effect in comfort ratings. 5. Total change of rear-foot angle and total change of Achilles tendon angle was 7-11 degree, 10-13 degree in top 10 shoe conditions by the two speed condition, respectively and they had little effect in comfort ratings. 6. Forefoot region hardness should not be under 50 degree. Otherwise, pronation moment in hip, knee, ankle joint were increased. 7. Bottom up phenomenon might not happen with over 40 degree in mid-sole hardness for subjects under 70kg of body weight. Specially, for subjects over 50kg, it is thought that bottom up phenomenon will not happen, so this finding will be useful for designing shoes. Specially, medio-lateral control was ranked the fourth in spite that LAST round of hill-counter region was big with shoes-size of 280mm (standard 270mm). This finding suggests future study that medio-lateral control has little to do with rear-foot round but might have something to do with motion patterns and mid-sole hardness. Additionally, it is founded that pronation moment in knee and ankle joint was small when mid-sole hardness was small. This finding is contrary to the findings of former studies which found that pronation movement would increase as mid-sole hardness in rear-foot region would decreased, therefore future study for examining this should be followed.
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