• 한국농림기상학회지
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• 제7권1호
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• pp.91-97
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• 2005

BYL-EV250 증발기록계를 이용하여 해남 농경지역의 자유 수면 증발량을 관측하였고, 그 자료를 분석하여, 기상 요소와 증발량과의 관계를 분석하였다. 자연상태에서 증발량을 결정하는 기상요소의 관계를 살펴보고, 그 결과를 바람과 포차의 경험식으로 나타내었다. 이 식을 이용하여 자유 수면으로부터의 시간당 증발량을 구할 수 있었으며 수온, 기온, 습도, 풍속 같은 기상요소만으로 증발량 추정이 가능했다. 증발량 산출에 대한 신뢰성을 높이기 위해 지속적으로 수면에서의 물수지에 대한 연구가 수행되어야 할 것으로 사료된다. 증발량 관측도 다른 기상요소와 같이 매시간 관측 자료 생산 가능성을 시사했다. 부력을 이용한 측정방법은 미소 수위 변화(0.1mm 이하)를 측정 할 수 있어 대형증발계를 활용한 자동관측에 대한 신뢰성을 확보할 수 있었다. 이 결과를 바탕으로 장기간 관측된 자유수면 증발자료와 플럭스 타워에서 동시에 관측된 실제 증발산 자료의 비교분석이 현재진행 중에 있다.

• 한국수자원학회논문집
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• 제49권2호
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• pp.165-175
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• 2016

본 연구에서는 일사량에 기초한 증발량 산정방법의 적용성을 검토하기 위해 기존에 연구자들에 의해서 제안된 식들을 3가지 형태의 model group (Model groups A, B, and C)으로 분류하고, 이를 우리나라 6개 지역(서울, 대전, 전주, 부산, 목포, 제주)에 적용하였다. 증발접시 증발량 자료를 이용하여 이들 model group들의 매개변수를 추정하고, 검증하였다. 또한 Penman (1948) 조합식을 적용하여 이들 model group들과 비교하였다. 연구결과에 의하면 모든 지역에서 Nash-Sutcliffe (N-S) 효율지수가 0.663 이상을 보여서 만족스러운 증발량 산정결과를 보였다. 모형 검증과정에서 산정된 N-S 효율지수는 모든 연구지역에서 0.526이상을 보여서 역시 만족스러운 결과를 보였으나, 부산지역에서 적용된 Model groups B와 C를 제외하고는 모두 Penman (1948) 조합식보다 작은 N-S 효율지수를 보였다. 따라서 주요 기상자료 일부(풍속, 상대습도)가 부족하거나 측정되지 않는 경우에 증발량 산정을 위해서 Penman (1948) 조합식을 대체하여 일사량자료에 기초한 증발량 산정 방법이 적용될 수 있을 것으로 사료된다.

• 대한전자공학회논문지SD
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• 제44권11호
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• pp.43-50
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• 2007

ITO(Indium Tin Oxide) 전극 형성방법은 ITO 박막 자체의 전기 광학적 특성 뿐 아니라 ITO를 전극으로 하는 청색 발광 다이오드(파장 469nm)의 전기 광학적 특성 및 신뢰성에도 큰 영향을 미침을 확인하였다. 세 가지 ITO 전극 형성 방법 즉 electron beam evaporation법과 sputtering법, 그리고 electron beam evaporation법으로 먼저 증착한 뒤에 sputtering법으로 증착한 hybrid법 등을 사용하여 청색 발광 다이오드를 제작한 다음에 ITO 박막의 특성과 aging에 따른 발광 다이오드의 전기 광학적 특성 변화를 고찰하였다. 그 결과, ITO 전극을 sputtering 또는 electron beam evaporation 방법으로 형성한 발광 다이오드는 각각 sputtering damage의 문제와 전기저항이 증가하는 문제점을 안고 있음을 발견하였다. 그리고 이 문제점들을 hybrid 방법으로 해결하였다.

• 대한기계학회논문집
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• 제19권12호
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• pp.3317-3328
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• 1995

The objective of the present study is to predict the characteristics of heat and mass transfer around an evaporative condenser. Numerical calculations have been performed using multi-zone method to investigate heat transfer rate and evaporation rate with the variation of inlet condition(velocity, relative humidity and temperature) of the moist air, the flow rate of the cooling water and the shape of the condenser tube. From the results it is found that the profile of heat flux is the same as that of evaporation rate since heat transfer along the gas-liquid interface is dominated by the transport of latent heat in association with the vaporization(evaporation) of the liquid film. The evaporation rate and heat transfer rate is increased as mass flow rate increases or relative humidity and temperature decrease respectively. But the flow rate of the cooling water hardly affect the evaporation rate and heat flux along the gas-liquid interface. The elliptic tube which the ratio of semi-minor axis to semi-major axis is 0.8 is more effective than the circular tube because the pressure drop is decreased. But the evaporation rate and heat flux shown independency on the tube shape.

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.552-559
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• 2005

The evaporation pressure drop of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth. horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$, saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation pressure drop of $CO_2$ are highly dependent on the vapor qualify, heat flux and saturation temperature. The evaporation pressure drop of $CO_2$ is very lower than that of R-22. In comparison with test results and existing correlations. the best fit of the present experimental data is obtained with the correlation of Choi et al. But existing correlations failed to predict the evaporation pressure drop of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation pressure drop of $CO_2$ in a horizontal tube.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1725-1734
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• 1996

Experimental condensation and evaporation heat transfer coefficients were measured in a horizontal smooth tube and a horizontal micro-finned tube with HFC-134a. The test sections are straight, horizontal tubes with have a 9.52mm outside diameter and about 5000mm long. The micro-finned tube had 60 fins with a height of 0.12mm and a spiral angle of 25.deg.. The condensation test section was a double-pipe type with counter flow configuration. The evaporation test section employed an electic heating method. Enhancement factors which is defined as a ratio of the heat transfer coefficient for micro-finned tube to that for smooth tube, varied from 1.3 to 1.6(mass flux:110~190kg/m$^{2}$s) for condensation and 1.2 to 1.5 (mass flux:70~160kg/m$^{2}$s) for evaporation. The experimental data of condensation and evaporation heat transfer coefficients were compared to several empirical correlations. Based on these comparisons, modified correlations of the condensation and evaporation heat transfer coefficient for both smooth and micro-finned tubes were proposed.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.74-83
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• 2007

This paper presents the experimental results of evaporation heat transfer coefficients of HC refrigerants (e.g. R290 and R600a). R-22 as a HCFCs refrigerant and R-l34a as a HFCs refrigerant in horizontal double pipe heat exchangers, having four different inner diameters of 10.07, 7.73, 6.54 and 5.80 mm respectively. The experiments of the evaporation process were conducted at mass flux of $35.5{\sim}210.4 kg/m^2s$ and cooling capacity of $0.95{\sim}10.1 kW$. The main results were summarized as follows : The average evaporation heat transfer coefficient of hydrocarbon refrigerants(R-290 and R-600a) was higher than the refrigerants, R-22 and R-l34a. In comparison with R-22 the evaporation heat transfer coefficient of R-l34a is approximately $-11{\sim}8.1 %$ higher. R-290 is $56.7{\sim}70.1 %$ higher and R-600a is $46.9{\sim}59.7 %$ higher. respectively. In comparison with experimental data and some correlations, the evaporation heat transfer coefficients are well predicted with the Kandlikar's correlation regardless of a type of refrigerants and tube diameters.

• 대한화학회지
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• 제48권5호
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• pp.527-536
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• 2004

이 연구에서는 가열 상황과 비가열 상황을 비교하여 증발과 끓음에 대한 고등학교 3학년 122명의 학생들과 화학 전공 97명의 교사들의 인식을 조사하였다. 연구 결과, 교사들은 과학적 개념을 대부분 가지고 있었으며 상황에 따른 변화가 거의 없었으나, 학생들은 가열 상황에서는 증발을 끓음으로, 비가열 상황에서는 끓음을 증발로 인식하는 비율이 높았다. 교과서의 증발과 끓음에 대한 설명 유형을 분석한 결과, 많은 교과서에서 증발은 비가열 상황에서만 제시하고, 끓음은 가열 상황에서 제시하는 것으로 나타났다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.662-665
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• 2008

We experimentally investigate the evaporation characteristics of water droplet on surfaces of various wettabilities in the range of contact angle from 30$^{circ}$ to 150$^{circ}$. When a liquid droplet on a solid surface evaporates, the contact angle generally decreases with time and the evaporation rate varies with the droplet geometry such as the contact angle and the radius of curvature. Experimental data on the contact angle as a function of the droplet volume obtained by digital image analysis techniques cannot be explained by the existing theories. By measuring the temporal evolutions of the droplet radius and contact angle, we find the qualitative difference between the evaporation patterns on the hydrophilic surfaces where the contact radius remains constant initially and those on the superhydrophobic surfaces where the contact angle remains constant. Also, the evaporation rate is observed to depend on the surface material although the currently available models assume that the rate is solely determined by the droplet geometry. Despite the fact that the theory to explain this dependence on the surface remains to be pursued by the future work, we give the empirical relations that can be used to predict the droplet volume evolution for each surface. It is expected that the present study will contribute to interpreting the effect of droplet geometry on the evaporation.

• 대한기계학회논문집B
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• 제31권4호
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• pp.313-319
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• 2007

The effect of capillary cross-section geometry on evaporation is investigated in terms of the meniscus shape, evaporation rate and evaporation-induced flow for circular, square and rectangular cross-sectional capillaries. The shapes of water and ethanol menisci are not much different from each other in square and rectangular capillaries even though the surface tension of water is much larger than that of ethanol. On the other hand, the shapes of water and ethanol menisci are very different from each other in circular capillary. The averaged evaporation fluxes in circular and rectangular capillaries are measured by tracking the meniscus position. At a given position, the averaged evaporation flux in rectangular capillaries is much larger than that in circular capillary with comparable hydraulic diameter. The flow near the evaporating meniscus is also measured using micro-PIV, so that the rotating vortex motion is observed near the evaporating ethanol and methanol menisci except for the case of methanol meniscus in rectangular capillary. This difference is considered to be due to the existence of corner menisci at the four comers.