• Ocean and Polar Research
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• 제27권3호
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• pp.237-250
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• 2005

To investigate the air mass modification related with Yeongdong Heavy snowfall events, we examined sensible and latent heat fluxes on the East Sea, the energy exchange between atmosphere and ocean in this study. Sensible and latent heats were calculated by a bulk aerodynamic method, in which NCEP/NCAR reanalysis data and NOAA/AVHRR weekly SST data with high resolution were used. Among winter precipitation events in the Yeongdong region, 19 heavy precipitation events $(1995{\sim}2001)$ were selected and classified into three types (mountain, cold-coastal, and warm types). Mountain-type precipitation shows highly positive anomalies of sensible and latent heats over the southwestern part of the East Set When separating them into the two components due to variability of wind and temperature/ specific Humidity, it is shown that the wind components are dominant. Cold-coastal-type precipitation also shows strong positive anomalies of sensible and latent heats over the northern part and over the central-northern part of the East Sea, respectively. It is shown that the sensible heat anomalies are caused mostly by the decrease of surface air temperature. So it can be explained that cold-coastal-type precipitation is closely related with the air mass modification due to cold air advection over warm ocean surface. But in warm-type precipitation, negative anomalies are found in the sensible and latent heat distributions. From this result, it may be postulated that warm-type precipitation is affected by the internal process of the atmosphere rather than the atmosphere-ocean interaction.

• 한국태양에너지학회 논문집
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• 제32권3호
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• pp.68-76
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• 2012

Since the solar energy resource is the main input for sizing any solar energy utilization system, it is essential to utilize the solar radiation data as an application and development of solar energy system increase. It will be necessary to understand and evaluate the insolation data. The Korea Institute of Energy Research(KIER) has begun collecting horizontal global insolation data since May, 1982 at 16 different locations in Korea and for the more detailed analysis, images taken by geostationary satellite may be used to estimate solar irradiance fluxes at earth's surface. It is based on the empirical correlation between a satellite derived cloud index and the irradiance at the ground. From the results, the measured data has been collected at 16 different stations and estimated using satellite at 44 different stations over the Korean peninsula from 1982 to 2010. The Result of analysis shows that the annual-average daily global radiation on the horizontal surface is 3.66 $kWh/m^2/day$ and estimated solar radiation fluxes show reliable results for estimating the global radiation with average deviation of -7.2 to +3.7 % from the measured values.

• 설비공학논문집
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• 제25권3호
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• pp.143-149
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• 2013

In this work, nucleate pool boiling heat transfer coefficients (HTCs) of R134a and R1234yf are measured, on flat plain, 26 fpi low fin, Turbo-B, Turbo-C and Thermoexcel-E surfaces. All data are taken at the liquid pool temperature of $7^{\circ}C$, on a small square copper plate ($9.53mm{\times}9.53mm$), at heat fluxes from $10kW/m^2$ to $200kW/m^2$, with an interval of $10kW/m^2$. Test results show that nucleate boiling HTCs of all enhanced surfaces are greatly improved, as compared to that of a plain surface. Nucleate pool boiling HTCs of R1234yf are very similar to those of R134a, for the five surfaces tested.

• 대기
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• 제28권4호
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• pp.383-392
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• 2018

This study investigates synoptic characteristics of cold surges over South Korea during winter season (December-February). A total of 63 cold events are selected by quantile regression analysis using daily mean temperature observations from 11 KMA stations for 38 years (1979/80-2016/17). Large-scale pressure pattern during the cold surges is well characterized by high over Siberia and low over Aleutian regions, which elucidates cold advection over the Korean peninsula. However, the large-scale pattern cannot successfully explain the observed sudden decrease of temperature during the cold surges. Composite analyses reveal that a synoptic-scale cyclone developing over the northern Japan is a key feature that significantly contribute to the enhancement of cold advection by increasing pressure gradient over the Korean peninsula. Enhanced sensible and latent heat fluxes are observed over the southern ocean of Korea and Japan during the cold surges due to temperature and humidity differences between the near surface and the lower atmosphere over the ocean. The evaporated water vapor transported toward the center of the surface cyclone and condenses in the lower-to-middle troposphere. The released energy likely promotes the development of the surface cyclone by inducing positive PV near the surface of the heating region.

• 대한환경공학회지
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• 제22권7호
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• pp.1273-1284
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• 2000

본 연구에서는 한외여과막을 이용하여 수중에 함유되어 있는 부식산의 제거실험을 수행하였다. 한외여과성능에 미치는 공정변수들의 영향이 비선형적으로 서로 얽혀 있기 때문에, 응답표면분석법(RSM)을 이용하여 분리막 공정의 최적화와 각 변수간의 상호관계 및 투과성능에 영향을 미치는 공정변수(압력, 농도, 유량 등)들이 분리성능에 미치는 영향을 분석하였다. 부식산용액의 공정변수에 대한 투과량의 변화는 유입용액의 부식산의 농도가 10ppm, 40ppm 70ppm으로 증가함에 따라 2.56, 2.27, $2.10({\times}10^{-2}cc/cm^2{\cdot}min)$으로 감소하였다. 즉, 순수한 물의 투과량에 비해 각각 17.7%, 26.7%, 32.2%만큼 감소하였으며, 투과부에서의 부식산농도는 0.5, 1.2ppm, 2.1ppm으로 증가하였다. 막내에서의 압력차를 1atm, 2atm, 3atm으로 변화하였을 때, 1atm에서의 투과량보다 각각 66%, 152%로 증가하였으며, 투과부에서의 부식산의 농도도 각각 0.5ppm, 1.5ppm, 3.5ppm으로 증가하였다. 응답표면분석(RSM)에 의하면 공정변수의 최적운전조건은 유입부식산농도 38.8~40ppm, 유입유량 30~30.7cc/min, 압력차는 2atm이었다.

• Asian Journal of Atmospheric Environment
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• 제6권4호
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• pp.246-258
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• 2012

Particulate matter deposited on leaf surfaces may cause erosion/abrasion of epicuticular wax and the malfunction of stomata. However, the deposition processes of particulate matter, such as elemental carbon (EC), has not been studied sufficiently in Asian forest ecosystems. Deposition processes for particulate ${SO_4}^{2-}$ and EC were studied in a Japanese cedar forest in Kajikawa, Niigata Prefecture, Japan, and in a dry evergreen forest and a dry deciduous forest in Sakaerat, Nakhon Ratchasima province, Thailand. The ${SO_4}^{2-}$ fluxes attributed to rainfall outside the forest canopy (RF), throughfall (TF), and stemflow (SF) showed distinct seasonalities at both sites, increasing from November to February at the Kajikawa site and in March/April at the Sakaerat site. Seasonal west/northwest winds in winter may transport sulfur compounds across the Sea of Japan to the Kajikawa site. At the Sakaerat site, pollutants suspended in the air or dry deposits from the dry season might have been washed away by the first precipitations of the wet season. The EC fluxes from RF and TF showed similar variations by season at the Kajikawa site, while the flux from TF was frequently lower than that from RF at the Sakaerat site. Particulate matter strongly adsorbed onto leaf surfaces is not washed away by rainfall and contributes to the EC flux. At the Kajikawa site, Japanese cedar leaf surfaces accumulated the highest levels of particulate matter and could not be neglected when calculating the total flux. When such leaf-surface particles were considered, the contribution of dry deposition to the total EC flux was estimated to be 67%, 77%, and 82% at the Kajikawa site, and at the evergreen and deciduous forests of the Sakaerat site, respectively. Leaf-surface particles must be included when evaluating the dry and total fluxes of particulate matter, in particular for water-insoluble constituents such as EC.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.447-452
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• 2001

Quenching phenomena of hemispherical downward facing convex surfaces with narrow gaps have been investigated experimentally. Experiments employed test sections having 1 and 2 mm in gap thickness and 1 atm in system pressure. From interpretations of the temperature and the heat flux history, it was found that the flooding inside the gap was restricted by CCFL phenomena and quenching process was propagated from lower to upper region of the internal copper shell. The ratio of the maximum heat fluxes at 1 mm to 2mm in gap thickness was the almost same that obtained by steady state experiments. The quenching scenario of the hemispherical downward facing surface with narrow gap has been suggested.

• 설비공학논문집
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• 제15권12호
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• pp.1007-1017
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150∼250 kg/$m^2$s with air flows at velocity ranges from 0.3 m/s to 0.8 m/s.

• 조명전기설비학회논문지
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• 제23권8호
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• pp.21-25
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• 2009

속도와 토크의 값이 다른 5개의 동작점에서 효율이 최대가 되는 자속을 구한 후, 5개의 자속을 이용하여 효율이 최대가 되는 자속의 곡면을 구한다. 주어진 속도와 토크를 이용하여 자속곡면에서 효율이 최대가 되는 자속을 구한 후, 이 자속을 초기값으로 하여 미리 정해진 양만큼 자속을 변화시키면서 최대효율제어를 수행한다. 시뮬레이션 결과 제안한 방법에 의하여 신속히 최대효율제어를 위한 자속으로 수렴함을 보인다.

• 대한기계학회논문집B
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• 제21권11호
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• pp.1466-1474
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• 1997

In order to design and develop a spark ignition engine, many studies must be preceded about the characteristics of thermal flow. For measurement of transient wall temperature thin film thermocouples of Bendersky type were manufactured and these probes were fixed into the wall of combustion chamber. Surface wall temperatures were measured in experiments of various engine speeds. Transient heat fluxes were calculated from the wall temperature measurements. Pressure was measured from combustion chamber using pressure transducer and gas temperatures were calculated using the state equation of ideal gas. And instantaneous heat transfer coefficients were obtained. It will be the basic data for the formulae of instantaneous heat transfer coefficients.