• Journal of Biosystems Engineering
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• 제22권4호
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• pp.459-468
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• 1997

To optimize the design and operation of a soil- air heat exchanger system, the effects of variables characterizing system design and operation on the performance of the system were analyzed by a theoretical model which included the three-dimensional transient heat conduction equation. The solution of the theoretical model was acquired by a computer program that uses Finite Difference Methods and Gauss-Seidel iteration computation, in which the time discretization scheme was an implicit difference appoximation. The computer program was validated first by comparison of the results for different grid sizes. Air outlet temperature, energy gain, and heat exchange efficiency of the system were analyzed based upon the tube diameter, tube length, tube thickness, and tube thermal diffusivity.

• 한국환경과학회지
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• 제15권6호
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• pp.527-532
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• 2006

The purpose of this study is to clarify the characteristic of urban heat island intensity in urban area formed at a basin. Thermal environments for basin-type cities are influenced by significant topographic relief winds. In this study, we analyzed the diurnal variations of the heat island intensity according to meteorological condition and season using AWS(Automatic Weather observation System) data in Daegu Metropolitan area for 1 year(3/April, 2003 $\sim$ 2/April, 2004). In this study, we defined the urban heat island intensity as the air temperature difference between two points, the downtown and the suburban area. The suburban area is located at valley mouth around the western tip of Daegu. The results are summarized as follows; 1. The maximum heat island intensity was recorded at early morning under the meteorological conditions, calm and clear 2. The heat island intensity was strong in the order of winter, fall, spring and summer. 3. The heat island intensity came out minus values in the afternoon. This phenomenon is known as a com mon for basin-type cities. 4. The heat island intensity was twice or more in clear and calm than not so.

• 한국지구과학회지
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• 제39권1호
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• pp.1-22
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• 2018

Eight different data sets are examined in order to gain insight into the surface heat flux traits of the East Asian marginal seas. In the case of solar radiation of the East Sea (Japan Sea), Coordinated Ocean-ice Reference Experiments ver. 2 (CORE2) and the Objectively Analyzed Air-Sea Fluxes (OAFlux) are similar to the observed data at meteorological stations. A combination is sought by averaging these as well as the Climate Forecast System Reanalysis (CFSR) and the National Centers for Environmental Prediction (NCEP)-1 data to acquire more accurate surface heat flux for the East Asian marginal seas. According to the Combination Data, the annual averages of net heat flux of the East Sea, Yellow Sea, and East China Sea are -61.84, -22.42, and $-97.54Wm^{-2}$, respectively. The Kuroshio area to the south of Japan and the southern East Sea were found to have the largest upward annual mean net heat flux during winter, at -460- -300 and at $-370--300Wm^{-2}$, respectively. The long-term fluctuation (1984-2004) of the net heat flux shows a trend of increasing transport of heat from the ocean into the atmosphere throughout the study area.

• 한국지구과학회지
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• 제25권7호
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• pp.629-636
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• 2004

구름이 유입하는 경우 해양대기경계층의 발달을 분석하기 위하여, 울릉도에서 관측한 레윈존데 자료와 AWS 자료, 위성사진, 동해에 설치된 부이 자료를 이용하였다. 이 자료를 이용하여 열의 이류와 표층 열속, 구름 유입에 따른 복사에너지를 추정하였다. 혼합층 내의 열 변화 및 혼합층의 발달을 표층 열속과 구름에 의한 장파복사속으로 설명하였다. 열속의 변화를 알아보기 위해 벌크법을 이용하였다. 울릉도, 동해상의 부이, 포항에서 관측한 자료를 이용한 열수지 방정식으로 대기경계층의 열보존 관계를 분석하였다. 구름의 유입으로 인해 일몰 후 지면의 복사냉각이 방해되고, 구름에서 장파복사가 방출된다. 그로 인해 야간에 오히려 기온이 증가하였다. 또 남서쪽으로부터 따뜻한 공기가 이류되어, 하층 대기의 온도를 증가시켰다. 이러한 이유로 혼합층이 파괴되지 않고, 잔류층을 형성하며 남아있었다.

• 한국기후변화학회지
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• 제9권3호
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• pp.209-221
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• 2018

The characteristics of heat wave events in Seoul are analyzed using weather station data from Korea Meteorological Administration (KMA) and European Centre for Medium-Range Weather Forecast (ECMWF) ERA-Interim reanalysis data from 1979 to 2016. Heat waves are defined as events in the upper 10th percentile of the daily maximum temperatures. The associated synoptic weather patterns are then classified into six clusters through Self-Organizing Map (SOM) analysis for sea-level pressure anomalies in East Asia. Cluster 1 shows an anti-cyclonic circulation and weak troughs in southeast and west of Korea, respectively. This synoptic pattern leads to southeasterly winds that advect warm and moist air to the Korean Peninsula. Both clusters 2 and 3 are associated with southerly winds formed by an anti-cyclonic circulation over the east of Korea and cyclonic circulation over the west of Korea. Cluster 4 shows a stagnant weather pattern with weak winds and strong insolation. Clusters 5 and 6 are associated with F?hn wind resulting from an anti-cyclonic circulation in the north of the Korean Peninsula. In terms of long-term variations, event frequencies of clusters 4 and 5 show increasing and decreasing trends, respectively. However, other clusters do not show any long-term trends, indicating that the mechanisms that drive heat wave events in Seoul have remained constant over the last four decades.

• 열처리공학회지
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• 제8권4호
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• 설비공학논문집
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• 제5권3호
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• pp.226-233
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• 1993

Thermosyphons are simple devices that can passively transport thermal energy over relatively large distance with little temperature degradation. Especially, the thermosyphon system requires no costly energy input and is completely maintenance free. These attributes permit the use of low grade thermal energy for thermal control of structures including the stabilization of highway foundations. This paper presents the experimental results of the snow melting system in which thermosyphon was utilized to ransfer the earth energy to the pavement to remove snow and ice. The test facility, three earth heated and one unheated test panels, is designed to investigate the variables associated with removing snow and ice from pavement surfaces. The results of these test show that the earth heated panel surface temperature is higher $2{\sim}6^{\circ}C$ than unheated panel when the ambient air temperature is $-7^{\circ}C$. The thermal performance of this earth source thermosyphon system for road heating showed that there was no snow on the heated test panels when the snowfall was 5cm average for the region.

• 한국산업융합학회 논문집
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• 제7권4호
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• pp.331-340
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• 2004

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space. The fresh air is introduced into the double slab space and passes through the opening bored into the footing beam. The air is cooled by the heat exchange with the inside surface of the double slab space in summer, and heated in winter. This system not only reduces sensible heat load of the fresh air by heat exchange with earth but also reduces latent heat load of the fresh air by ad/de-sorption of underground double slab concrete. In this paper, we used a model for evaluation of fresh air latent heat load reduction by hygroscopic of air to earth exchange system taking into account coupled heat and moisture transfer of underground double floor space. In conclusion it shows the validity of the proposed method for a design tool and the quantitative effect of the system.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1995년도 정기학술강연회 발표논문 초록집
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• pp.20-25
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• 1995

Surface wind field over an ocean plays a very important role not only to generate wind-driven current, but also to control heat exchange between ocean and atmosphere. However, the surface wind-field used for the ocean circulation and heat exchange is usually estimated by indirect methods because of lack of observed wind data and incomplete spatial coverage. (omitted)

• Ocean and Polar Research
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• 제43권1호
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• pp.15-30
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• 2021

In this study, using 16 ORA-IP (Ocean Reanalysis Intercomparison Project) data, we investigated spatial and temporal changes of net surface heat flux in the East Asian seas and presented a new ensemble net surface heat flux index. The ensemble net surface heat flux index is produced considering the data distribution and the standard deviation of each ORA-IP. From the correlation analysis with air temperature averaged over the Korean Peninsula, ensemble net heat flux around the Korea Strait shows the highest correlation (0.731) with a 3 month time lag. For the correlation study regarding precipitation over the Korean Peninsula, it also shows significant correlation especially in winter and spring seasons. Similar results are also found in comparison with climate indices (AO, PDO, and NINO3.4), but ensemble net surface heat flux data in winter season reveals the strongest correlation patterns especially with winter temperature and spring precipitation.