• 한국포장학회지
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• 제23권1호
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• pp.9-15
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• 2017

수증기 및 산소에 대한 차단성이 개선된 PVA-BA 코팅 조성액의 포장소재로의 적용가능성을 확인하기 위하여 콤마 코팅과 라미네이션 공정을 이용하여 PET/PVA-BA/OPP 다층필름을 제조하였다. PCT 전 후의 PET/PVA-BA/OPP 다층필름의 기체, 수증기 차단특성 및 인장강도를 확인하였고 이를 PA/PA/EVOH/PP 다층필름의 물성과 비교하였다. PVA내 BA 함량이 증가함에 따라 물성이 증가하는 것을 확인할 수 있었지만, PCT 후 PET/PVA-BA/OPP 다층필름의 산소, 수증기 차단특성 및 인장강도는 감소하는 경향을 보였다. 이는 PVA-BA층 내 증가한 가교밀도와 관련이 있는 것으로 판단된다. 또한, 조미김을 이용한 저장특성분석에서, PET/PVA-BA/OPP다층필름은 PP/Al-metallized PP 다층필름에 비해 조미김의 지방산화를 야기시키는 요인을 효과적으로 억제하는 것으로 판단된다. 하지만, PP/Al-metallized PP 다층필름에 비해 PET/PVA-BA/OPP 다층필름의 상대적으로 높은 수분투과특성 때문에 Aw에 큰 장점을 확인하지 못하였다. 따라서, 물성 극대화 및 포장소재로 적용을 위해서는 PET/PVA-BA/OPP 다층필름 내 수분 차단성 향상에 대한 추가적인 연구가 필요하다는 것을 확인하였다.

• 한국태양에너지학회 논문집
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• 제34권4호
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• pp.111-122
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• 2014

The purpose of this study is to understand daily variation of short-wave radiation trends according to the state of surface and observation of atmosphere conditions in downtown and suburban observation area. The followings are main results from this study. 1) We found out daily air temperature variation of downtown is less than that of suburban area because of bigger heat capacity of artificial elements such as massive buildings and pavements. 2) It is more effective to estimate of air condition by water vapor pressure than relative humidity in the atmosphere. 3) The difference of solar radiation ratio between downtown and suburban area is dependant on different atmosphere conditions at two observation stations.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.131-139
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• 2001

Highly accurate control of the air-fuel ratio is important to reduce exhaust gas emissions of the gaseous-fuel engines. In order to achieve this purpose, inlet air mass flow must be measured exactly, and precise engine models are necessary to design engine control systems. In this paper, the effects of water vapor and gaseous fuel that change the air mass flow are studied. The effective air mass ratio is defined as the air mass flow divided by the mixture mass flow, and also it is applied to the estimation of the inlet air mass flow. The presence of the gaseous fuel and the water vapor in the mixture reduces the air partial pressure and the effective air mass ratio of the gaseous-fuel engines. The Experimental results for an LPG engine show that the estimation of the inlet ai mass flow based upon the effective air mass ratio is more accurate than that of the normal air mass flow.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.334-337
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• 2003

장마포기에는 적도에서 동지나 지역은 주로 대류에 의한 강수가 우세했으며, 대다수의 수증기는 인도 몬순지역에서 이류되어 온 수증기임을 안 수 있었다. 장마기에는 한반도 지역은 convection에 의한 강수는 미소하나 microphysics에 의한 강수가 지배적이었다. 이 때 수증기의 근원(강수량)은 인도 몬순지역에서 이류되어 온 수증기이다. 비장마기에 우리나라 및 대다수의 지역은 microphysics에 의한 강수가 지배적이었다. 또한 태풍의 북상으로 인한 대량의 수증기의 이류이다. 수증기의 대부분은 Rossby wave의 복동방향 전파에 기인한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.241-246
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• 1996

An analytical model to calculate rate of vapor generation due to heterogeneous wall nucleation in flashing flow is developed. In the present model, an important parameter of the vapor generation term, i.e. nucleation site density is calculated by integrating its probability distribution function with respect to active cavity radius. The limits of integration are minimum and maximum active cavity radii, and these are formulated using an active cavity model for nucleate boiling. This formulation, therefore. can statistically account for the effect of surface specific thermo-physical and geometric conditions on the vapor generation rate and flashing inception. For verifying the adequacy of the present model, steady state two-fluid and the bubble transport equations are solved with applicable constitutive equations. The applicable region of the bubble transport equation is also extended to churn-turbulent flow regime to predict interfacial area concentration at high void fraction. Predicted results in terms of axial pressure and void fraction profiles along the channels are compared with experimental data of Super Moby Dick and BNL Reasonable agreements have been achieved and this shows the applicability of the present model to flashing flow analysis.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.759-764
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• 2005

In this paper, numerical analysis of hydrogen recycle system has been conducted in order to enhance the efficiency of automotive fuel cell. Generally, the excess hydrogen is provided in the automotive fuel cell. Since the non-reaction hydrogen reduces automotive fuel cell efficiency, reuse of the non-reaction hydrogen can be helpful to improve the fuel cell performance. In case of PEM FC, the water vapor is provided to hydrogen from the cathode so that the mixture experiences phase change depending on the changes of pressure and temperature. The internal flow of the mixture in the hydrogen recirculation system of fuel cell was investigated for real flow conditions. The variation of performance, properties and mass fractions of mixture, hydrogen and water-vapor were investigated. This study was performed based on 80KW level automotive fuel cell's recycling system.

• 설비공학논문집
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• 제14권6호
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• pp.468-476
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• 2002

This paper deals with heat and mass transfer characteristics and performance evaluation of a counter flow double-tube condenser for a multi-component refrigerant mixture. The local heat and mass transfer characteristics of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a are evaluated for a counter flow double-tube condenser cooled by water. Then, the local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, heat flux and condensation mass flux are obtained. The heat exchange performance for ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a on the total pressure drop and the heat transfer characteristics are also compared with those for R404A, R410A, R502, R22, R32, Rl23 and R134a.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.921-930
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• 2001

A new theoretical critical heat flux (CHF) model was developed for the forced convective flow boiling at high pressure, high mass velocity, and low quality. The present model for an intermittent vapor blanket was basically derived from the sublayer dryout theory without including any empirical constant. The vapor blanket velocity was estimated by an axial force balance, and the thickness of vapor blanket was determined by a radial force balance for the Marangoni force and lift force. Based on the comparison of the predicted CHF with the experimental data taken from previous studies, the present CHF model showed satisfactory results with reasonable accuracy.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4776-4797
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• 2022

In the one-dimensional thermal-hydraulic (TH) codes, a subcooled boiling model to predict the void fraction profiles in a vertical channel consists of wall heat flux partitioning, the vapor condensation rate, the bubbly-to-slug flow transition criterion, and drift-flux models. Model performance has been investigated in detail, and necessary refinements have been incorporated into the Safety and Performance Analysis Code (SPACE) developed by the Korean nuclear industry for the safety analysis of pressurized water reactors (PWRs). The necessary refinements to models related to pumping factor, net vapor generation (NVG), vapor condensation, and drift-flux velocity were investigated in this study. In particular, a new NVG empirical correlation was also developed using artificial neural network (ANN) techniques. Simulations of a series of subcooled flow boiling experiments at pressures ranging from 1 to 149.9 bar were performed with the refined SPACE code, and reasonable agreement with the experimental data for the void fraction in the vertical channel was obtained. From the root-mean-square (RMS) error analysis for the predicted void fraction in the subcooled boiling region, the results with the refined SPACE code produce the best predictions for the entire pressure range compared to those using the original SPACE and RELAP5 codes.

• 생물환경조절학회지
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• 제16권3호
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• pp.174-179
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• 2007

참외 발효과 발생에 영향을 미치는 증산과 관련된 몇 가지 요인을 검토한 결과는 다음과 같다. 참외의 증산율은 지온이 높고 토양수분 함량이 많을수록 높았으며, 광도가 약하여 온도가 낮을 경우 증산율과 기공 전도도가 낮아졌고, 저온 다습한 기상조건에 의한 증산의 억제는 식물체와 대기사이의 증기압기울기가 낮아지는 것으로 생각된다. 발효과 발생은 과실의 비대가 느린 착색기 이후에 토양수분이 -10 kPa로 많고, 저온 다습하여 참외와 대기 사이에 증기압기울기가 낮게 형성되어 증산이 억제될 때 발생하였다. 따라서 참외의 발효과 발생은 착색기 이후 참외의 과실 비대가 지연되는 반면 지온이 높아 뿌리로부터 지상부로 수분의 공급이 원활하고, 저온 다습한 기상조건하에 수분의 증산이 억제되어 수분이 태좌부로 유입되면 발효과가 발생되는 것으로 생각된다.