• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.1-6
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• 2000

In this study, We evaluated the Performance of PFC and the system performance of large size air-conditioner applying to outdoor condenser. PFC can meet the same cooling capacity in 40.42% of volume to fin-tube condenser. Although the fin-tube condenser requires 3600g of refrigerant charging, PFC requires 1700g, 1800g, 1900g, 2000g refrigerant charging for each 2.0mm, 2.5mm, 3.0mm and 3.5mm fin pitches. Difference of condensing and evaporation pressure is the biggest point 2.0mm fin pitch and the smallest point 2.5mm fin pitch.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3546-3552
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• 2009

본 연구에서는 천정 설치형 공조기 적용을 위해 연구가 활발히 진행되고 있는 알루미늄 평행류 증발기 해석 프로그램을 개발하여 190mm*650mm*25mm(W*H*D) 크기의 열교환기를 해석하였다. R410A냉매의 분배비가 일정하고 상하로 유동하는 2, 3 패스의 경우와 3 패스이고 분배비율(1:1:1, 1:2:2)을 달리할 때, 열교환 성능을 예측하였다. 계산 결과, 2 패스가 3 패스보다 국소 전열량이 30% 정도 높았지만, 건도에 따른 열전달계수는 25% 낮았으며, 3 패스의 경우, 분배비 1:1:1 보다 1:2:2가 냉매 압력손실이 높게 나타났다. 본 해석에서는 패스당 냉매가 균일하게 분포하는 것으로 가정하였으므로, 패스별로 불균일하게 유동되는 실제의 경우보다 열교환성능을 과대 예측하는 것으로 판단된다.

• 한국진공학회지
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• 제16권5호
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• pp.388-396
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• 2007

KSTAR (Korea Superconducting Tokamak Advanced Research) 전류인입선(CL; Current Lead)은 4.5 K의 저온에서 운전되는 초전도 버스라인과 300 K의 실온에서 운전되는 MPS (Magnet Power Supply)를 전기적으로 연결하는 장치이다. 초기 플라즈마 발생시험을 위하여 TF (Toroidal Field) 및 PF (Poloidal Field) 리드박스에 전류인입선이 설치된다. TF 자석용 CL은 17.5 kA급 4 개의 CL에 최대 35 kA의 DC 전류가 인가되며, PF 자석용은 13 kA급 14 개의 CL에 350초간 $20\;{\sim}\;26\;kA$의 펄스 전류가 인가된다. 각각의 전류인입선은 TF 및 PF 자석에 전류를 인가하기 위한 버스라인이 연결되어 있으며, 전류인입선을 통해 초전도 버스라인으로 전달되는 전도열 및 전류인가시 발생되는 주울(Joule) 열을 차단하기 위한 헬륨냉매 제어시스템이 KSTAR 주장치와는 별도로 설치되어 있다. 리드박스 내 외부의 배관 및 제어시스템 설치완료 후 고진공 배기, 헬륨 누설검사, 전류인입선 유량 검사 및 액체질소 냉각시험을 실시하여 장치의 성능검증을 완료하였다.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.222-228
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• 2007

The effect of inclination angle on the heat transfer and pressure drop characteristics of brazed aluminum heat exchangers is experimentally investigated. Three samples having different fin pitches (1.25, 1.5 and 2.0 mm) were tested. Results show that heat transfer coefficient is not affected by the inclination angle. However, the friction factor increases as the inclination angle increases with negligible difference between the forward and backward inclination. Both the heat transfer coefficient and the friction factor are the smallest at $P_f$=1.5mm, followed by $P_f$=2.0mm and 1.25mm. Possible explanation is provided considering the louver layout. Comparison with existing correlations is also mad.