• 동력기계공학회지
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• 제17권3호
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• pp.44-49
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• 2013

The refrigerating system are high efficiency and comfortable due to the automation of the system as well as enhance energy saving are contributing to driving system. Previous study the rotational frequency of the compressor was confined to the fixed condition have changed load of evaporator and condenser related about the refrigerator performance characteristic according to the evaporation load and condensation load change tries to be analyze through the experiment. The useful data for the economic driving of the freezing apparatus tries to be drawn. Consequently, it confirmed that refrigerant in the compressor overheated and as the evaporation load increased the specific volume was increased and the coolant circulation rate decreased. In confirmed that condensation load increased the compression ratio and discharge gas temperature increased. It reduced the low-temperature efficiency and condensation calorie and the quality factor was decreased.

• 한국가시화정보학회지
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• 제14권2호
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• pp.18-24
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• 2016

This paper presents an experimental investigation to visualize cross-sectional two-phase flow structure and identify liquid-gas interface for condensation of steam at a low mass flux in a slightly inclined tube using the axial-viewing technique, which permits to look directly into flow during condensation of steam. In this technique, two-phase flow is viewed along the axis of a pipe by locating a high-speed video camera in front of a viewer that is fitted at the outlet of the pipe. A short section of the pipe is illuminated and is recorded through the viewer, which is kept free of liquid by mildly introducing air. Experiments were conducted in a pipe of 19.05 mm in inner diameter at atmospheric pressure. Cross-sectional two-phase flow structure is obtained at a steam mass flux of $2.62kg/m^2s$ as a function of steam quality in the range from 0.5 to 0.9. The results show that stratified-wavy flow is a unique flow pattern observed in the scope of the present study. Condensate film thickness, stratification angle and void fraction were measured from the obtained flow structure images. Finally, heat transfer coefficient was calculated using the measurement data and discussed in comparison with existing correlations.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1400-1409
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• 2023

In this study, three condensation models of the CUPID code, i.e., the resolved boundary layer approach (RBLA), heat and mass transfer analogy (HMTA) model, and an empirical correlation, were tested and validated against the COPAIN and CAU tests. An improvement on HMTA model was also made to use well-known heat transfer correlations and to take geometrical effect into consideration. The RBLA was a best option for simulating the COPAIN test, having mean relative error (MRE) about 0.072, followed by the modified HMTA model (MRE about 0.18). On the other hand, benchmark against CAU test (under natural convection and occurred on a slender tube) indicated that the modified HMTA model had better accuracy (MRE about 0.149) than the RBLA (MRE about 0.314). The HMTA model with wall function and the empirical correlation underestimated significantly, having MRE about 0.787 and 0.55 respectively. When using the HMTA model, consideration of geometrical effect such as tube curvature was essential; ignoring such effect leads to significant underestimation. The HMTA and the empirical correlation required significantly less computational resources than the RBLA model. Considering that the HMTA model was reasonable accurate, it may be preferable for large-scale simulations of containment.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.469-473
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• 2009

The supersonic gas ejector, as gas dynamic appliance, has been applied for a long time because of simplicity and reliability. However, for the prediction of ejector performances with given parameters, that is, working gas pressure and the nozzle shape, it is necessary to raise accuracy of modelling for properties of ejector gas flow. The purpose of the represented work is to compare one-dimensional modelling and numerical results with experimental results. The ejector with a conic nozzle has been designed and tested (Mach number at the nozzle exit section was 3.31, the nozzle throat diameter - 6 mm). Working gas - nitrogen, was brought from system of gas bottles. Diameter of the mixture chamber at the nozzle exit section was limited by condensation temperature of nitrogen and equaled 20 mm. The one-dimensional theory predicted the minimal starting pressure equaled 8.18 bar (absolute) and 0.051 bar in the vacuum chamber. Accordingly the minimal starting pressure was 9.055 bar and 0.057 in the vacuum chamber bar have been fixed in experiment.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.98-106
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• 2008

The motive gas of a supersonic ejector is supplied from different sources depending on the application. The performance of an ejector that is represented by the secondary flow pressure, starting and unstarting pressures heavily depends on the molecular properties of the motive gas. The effects of specific heat ratio of the motive gas were investigated experimentally for an axi-symmetric annular injection type supersonic ejector. Both the starting pressure and unstarting pressure, however, decreased with the increase of the specific heat ratio of the motive gas. It was discovered that the secondary flow pressure increased as the specific heat ratio of the motive gas decreased even if the stagnation pressure of the motive flow was invariant. However, when the motive gas flow nozzle area ratio is large enough for the motive gas to be condensed, different tendency was observed.

• Korean Chemical Engineering Research
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• 제53권4호
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• pp.496-502
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• 2015

탄화수소 이슬점은 천연가스 응축형태를 특성화하는 가장 일반적이고 자주 이용되는 물성으로 가스 품질 사양의 중요한 항목이다. 탄화수소 이슬점은 미량의 고탄화수소 성분에도 매우 민감한 것으로 알려져 있어, 특히 천연가스를 공급하는 가스 회사 입장에서는 기존 합의된 가스 사양을 만족하는 것 뿐만 아니라, 발생된 탄화수소 응축물에 의해 운영설비 및 안전에 심각한 문제를 일으킬 수 있으므로 탄화수소 이슬점을 정확하게 구하는 절차를 확립하는 것이 중요하다. 본 연구에서는 실제 현장조건 하에서 탄화수소 이슬점을 측정하기 위해 냉각 거울 방식의 이슬점 측정기를 설치, 운영하였으며, 측정된 이슬점 온도는 가스분석기에 의해 분석된 조성 및 천연가스 산업계에서 인정된 상태방정식을 이용하여 계산된 이슬점 온도와 비교하였다. 시험 결과 탄화수소 이슬점 측정기는 매우 안정되게 이슬점을 측정하였으며, 이슬점 측정기를 검증하기 위한 시험 가스로는 순수 프로판 가스가 적정하였다. 제조 표준가스 및 실제가스의 측정결과를 가스분석기에 의한 간접 측정 결과와 비교시에도 적정한 범위 내에서 일치하는 것을 확인하였다.

• 에너지공학
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• 제27권4호
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• pp.27-35
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• 2018

피동원자로건물냉각계통(PCCS)은 사고 발생 시 원자로건물로 방출된 열을 제거하여 원전의 건전성을 보장하기 위해 설계되었다. PCCS의 열제거 성능은 증기-공기 혼합물의 응축열전달에 의해 결정된다. 본 연구에서는 응축열전달계수의 예측 정확도를 향상시키기 위해 새로운 상관식을 이식한 MARS-KS 코드를 사용하여 PCCS의 열제거 성능을 평가하였다. MARS-KS 코드에 사용된 새로운 상관식은 압력, 벽면과냉도, 비응축성 기체 질량분율 및 응축튜브의 종횡비와 같은 열전달계수에 영향을 미치는 변수들을 이용하여 개발하였고, 이는 MARS-KS코드의 기본 응축 모델인 Colburn-Hougen 모델을 대체하여 적용되었다. 대형파단 냉각재상실사고 발생 시 PCCS의 운전에 따른 다양한 열수력학적 변수들을 분석하였고, 열제거 성능 평가를 위해 새로운 상관식이 적용된 MARS-KS 코드의 원자로건물 압력거동 계산결과와 기존의 응축모델을 이용한 해석결과를 비교하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.291-291
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• 2003

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2008년도 추계학술대회 논문집
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• pp.464-465
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• 2008

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2003년도 international symposium on advanced powder metallurgy
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• pp.118-118
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• 2003