• 한국대기환경학회지
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• 제21권3호
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• pp.303-313
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• 2005

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years $(2000\~2003)$ data at Chuncheon and the probability of prediction is investigated. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for $2\~4$ hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1m/s. Especially, about $42\%$ of foggy day fell on the calm $(0\~0.2\;ms^{-1})$ conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water surface temperature was calculated by using Water Quality River Reservoir System (WQRRS) and then it was used as the surface boundary condition of MM5. The numerical experiment was carried out for 2 days from 1300 LST on 14 October 2003 to 1300 LST on 16 October 2003 and fog was simulated at dawn on 15 and 16 October 2003. Simulated air temperature and dew point temperature indicate the similar tendency to observation and the simulated difference between air temperature and dew point temperature has also the similar tendency within $2^{\circ}C$. Thus, the occurrence of fog is well simulated in the terms of the difference between air temperature and dew point temperature. Horizontal distribution of the difference between air temperature and dew point temperature from the numerical experiment indicates occurrence, dissipation and lasting time of fog at Chuncheon. In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• 한국농림기상학회지
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• 제2권3호
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• pp.75-79
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• 2000

Calibrations of fast-response krypton hygrometers were carried out using a dew-point hygrometer to investigate the changes in their absorption coefficients due to long-term field operation. Absorption coefficients changed proportionally with the number of hours of field operation. The increase in absorption coefficient indicates that the water vapor flux, calculated with the original absorption coefficient, would underestimate the true flux in the field. To minimize the uncertainty in quantifying evapotranspiration and surface energy budget studies, frequent calibrations (for example, every 1500 hours of field operation) of krypton hygrometer are recommended.

• Journal of Mechanical Science and Technology
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• 제16권5호
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• pp.696-702
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• 2002

In the present paper, the effects of inlet pressure on the heat and mass transfer rates of an air cooler are numerically predicted by a local analysis method. The pressures of the moist air vary from 2 to 4 bars. The psychrometric properties such as dew point temperature, relative humidity and humidity ratio are employed to treat the condensing water vapor in the moist air when the surface temperatures are dropped below the dew point. The effects of the inlet pressures on the heat transfer rate, the dew point temperature, the rate of condensed water, the outlet temperature of air and cooling water are calculated. The condensation process of water vapor is discussed in detail. The results of present calculations are compared with the test data and shows good agreements.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.839-840
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• 2006

Sintering behavior of the Fe-0.8Mn-0.5C powder system was studied on the specimens with a density of ${\sim}7.0g/cc$ sintered at $1120^{\circ}C$ for 30 min in a gas mixture of $7%H_2/93%N_2$ with the inlet dew point of $-60^{\circ}C$. During the atmosphere monitoring ($CO/CO_2$-content and dew point) was showed, that carbothermical reduction occurs in two different temperature ranges; three peaks of dew point profile also can be distinguished during sintering cycle as well. Following sintering the Mn-content distribution and microstructures around the Mn-source were micro-analytical evaluated; the results showed that manganese travels through porous iron matrix up to ${\sim}60{\mu}m$.

• 한국수소및신에너지학회논문집
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• 제25권1호
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• pp.72-78
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• 2014

The study has been designed to develop water vapor supply for semiconductor industry, industrial gas manufacturing, impurities analysis, and fuel cell. Water concentration in air reached $1019{\mu}mol/mol$ at dew temp ($-20^{\circ}C$) and water concentration in CO2 reached $127{\mu}mol/mol$ at dew temp ($-40^{\circ}C$. Carbon dioxide needs more wet gas than air because interaction potential of carbon dioxide shows more strong attraction than air.

• 대한기계학회논문집B
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• 제36권4호
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• pp.457-463
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• 2012

최근 사용자의 편의성과 냉장고 저장 공간의 확보를 위해 냉장고 문과 내벽을 얇게 제작하고 있다. 따라서 냉기차단 벽두께의 감소로 인하여 내 외부 온도차가 일정수준 이상으로 발생하고 이에 따라 표면의 이슬 맺힘 현상이 문제가 되는데, 이는 냉장고 설계에 있어 해결되어야 할 중요한 문제이다. 문제를 해결하기 위해 지금은 일반적으로 전기히터와 같은 발열체를 사용하였는데, 이 경우에 불필요한 전력소모가 뒤따른다. 본 연구에서는 기존방식과 달리 전기를 사용하지 않고 기계적 구조변경을 통한 해결방안으로 가스켓 최적화와 냉동냉장실 내벽두께 조정을 통해 표면에 이슬 맺힘 현상을 저감하는 방법을 제안한다. 해석결과를 살펴보면, 히터의 사용 없이 이슬 맺힘이 발생하는 부분에서의 온도가 국부적으로 $0.39{\sim}3.07^{\circ}C$까지 상승하는 효과를 얻어서 이슬 맺힘 현상을 저감시켰다.

• 한국지구과학회지
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• 제40권6호
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• pp.624-638
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• 2019

절대 습도와 이슬점 온도의 관계에 대한 예비 교사들의 인식을 조사하기 위하여 설문지를 투입하였다. 설문 결과 예비 교사들이 "절대 습도와 이슬점 온도는 비례한다.", "이슬점 온도는 공기 중의 수증기의 질량에 비례한다."와 같은 견고한 오개념을 갖고 있음을 발견하였다. 예비 교사들이 갖는 이러한 오개념은 절대 습도와 이슬점 온도의 관계에 대한 7차 교육과정과 2007 개정 교육과정 중학교 과학 교과서의 부정확한 서술 내용에서 기인하는 것으로 사료된다. 한편, 2015 개정 교육과정 중학교 1학년 과학 교과서는 증발, 응결, 압력과 온도 변화에 따른 기체의 부피 변화를 분자운동의 관점에서 다루기 때문에, 중학교 교육과정에서 이러한 관점을 유지하기 위해 수증기량과 이슬점 온도의 척도로서 수증기압의 도입은 예비 교사와 학습자의 오개념을 방지할 수 있으며, 과학 교육과정을 보다 일관되고 논리적으로 만들 수 있을 것으로 사료된다.

• 조명전기설비학회논문지
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• 제29권1호
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• pp.64-69
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• 2015

This study investigates the Horizontal surface discharge characteristics of solid insulators by varying their materials, and the dew-point of dry-air. The methodology of this study is that a quasi-uniform field is first applied to a test chamber. Then, the chamber is filled with dry-air as an insulation gas which pressure is varied from 1 to 6atm while applying an AC voltage to the chamber. The used solid insulators are teflon, polyethlene and polyurethane. As the dew-point is lower and the pressure of dry-air is higher, the flashover voltage of all solid insulators increases more. When each characteristic of the solid insulators is compared under the same gas pressure, the flashover voltage of teflon is the highest. Then, the flashover voltage of polyethlene is higher than that of polyurethane. Moreover, it is observed that the flashover voltage increases as the horizontal distance between the electrodes of each solid insulator become larger, respectively. However, as the pressure is increased, flashover voltage of the solid insulators is saturated. Therefore, selection of cost-effective insulation is needed in order to appropriate pressure.

• 한국안전학회지
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• 제32권6호
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• pp.150-156
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• 2017

A frozen road surface increases traffic accidents during the winter season. Hence, information on easily-frozen road sections and their specificities are required to prevent traffic accidents. Frozen road surfaces are determined by equipment measuring road surface temperatures. However, there are limitations in investigating the entire road network. Therefore, it is imperative to develop new methods that effectively determine road surface freezing risks. Meteorologically, road surfaces are frozen when the actual temperature cools down to the dew point temperature. Under this condition, there is likely to be frost if relative humidity reaches 100% and frozen road surfaces as the temperature gets lower. Meteorological characteristics give us an alternative to a direct measurement road surface temperature to estimate risks of road surface freezing. Based on the clues, the relationship between severity of traffic accidents and temperature changes is empirically investigated using Paju weather data. The results reveal that as the temperature gets lower and changes in current temperature are relatively small, the severity of traffic accidents become higher. In addition, the same is true when the difference between current temperature and the dew point temperature is relatively small, as it increases possibilities of road surface freezing. Future studies must investigate how current temperature and the dew point temperature affect road surface freezing and thereby establish a time-space scope to estimate possible road surface freezing sections using only weather and road material type data. This would provide invaluable information for predicting and preventing frozen road accidents based on weather patterns.

• 대한기계학회논문집A
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• 제39권4호
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• pp.391-396
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• 2015

논문은 가장 보편화 되어있는 양문형 냉장고의 플랜지에서 이슬 맺힘 현상을 방지하기 위한 연구에 대한 논문이다. 양문형 냉장고는 냉동실과 냉장실을 분리하는 벽의 전면부를 플랜지라하고 여기에 양문의 개스킷이 밀착하여 냉기를 차단하는 역할을 한다. 플랜지의 철판에 맺히는 이슬을 방지하기 위해서 $35^{\circ}C$의 고온의 냉매가 흐르는 열선이 삽입된다. 하지만 열선을 삽입함에도 이슬 맺힘 현상이 계속되고 있는데 이것은 열선이 철판 하부에 밀착되지 않아 열선의 열이 철판 하부에 충분히 전달되지 않기 때문이다. 본 논문에서는 열선의 영향을 평가하고 열선과 철판 하부가 충분한 열전달을 할 수 있는 구조를 제안하고 그 타당한지 확인하였다.