• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.796-803
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• 2003

The discrete ordinates interpolation method (DOIM) has shown good accuracy and versatile applicability for the radiation $problems^{(1,2)}$. The DOIM is a nonconservative method in that the intensity and temperature are computed only at grid points without considering control volumes. However, when the DOIM is used together with a finite volume algorithm such as $SIMPLER^{(3)}$, intensities at the control surfaces need to be calculated. For this reason, a 'quadratic' and a 'decoration' schemes are proposed and examined. They are applied to two kinds of radiation problem in one-dimensional geometries. In one problem, the intensity and temperature are calculated while the radiative heat source is given, and in the other, the intensity and the radiative heat source are computed with a given temperature field. The quadratic and the decoration schemes show very successful results. The quadratic scheme gives especially accurate results so that further decoration may not be needed. It is recommended that the quadratic and the decoration schemes may be used together, or, one of them may be applied for control volume radiative energy balance.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.355-355
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• 2021

극한 폭염사상은 지난 20세기 이후 점점 더 빈번하게 발생하고 있으며, 더 광범위한 지역에서 발생하고 있다. 이러한 폭염사상은 다가오는 지구 온난화 시대에서 그 강도가 더 강해지고 지속기간이 길어질 것으로 예상되고 있다. 본 연구에서는 극한강우에 대한 강우강도-지속기간-빈도(intensity-duration-frequency, IDF)곡선의 개념을 폭염사상에 적용하여 미래의 극심한 폭염사상에 대한 발생확률, 강도 및 지속날짜(heat wave intensity-persistence day-frequency, HPF) 간의 관계를 확인해보고자 한다. 또한 해당 모델의 불확실성은 베이지안 기법을 이용하여 분석하였다. 우리나라 6개 주요 지역(대관령, 서울, 대전, 대구, 광주, 부산)에 대해 16개의 미래 일 최대 기온 앙상블 자료를 이용하여 비정상성 HPF곡선을 적용하였다. 미래 극한 폭염 앙상블 결과를 분석한 결과, 2050년을 기준으로 지속기간 2일에 대해 극한 폭염의 강도가 RCP 4.5 이하 시나리오 기준 1.23 ~ 1.69 ℃ 범위에서 상승할 가능성이 높은 것으로 나타났으며, RCP 8.5 이하 시나리오 기준의 경우 1.15 ~ 1.96 ℃ 범위로 나타났다. 또한 HPF 모델의 매개변수 추정으로 인한 불확실성의 경우, 다양한 기후 모델의 변동성으로 인한 불확실성보다 크게 나타났다. 모델의 매개변수 추정에 따른 불확실성을 반영한 결과, 2010~2050년에 해당하는 폭염의 강도에 대한 delta change의 95% 신뢰구간은 RCP 4.5 이하에서 0.53 ~ 4.94 ℃, RCP 8.5 이하에서 0.89 ~ 5.57 ℃로 나타났다.

• The KSFM Journal of Fluid Machinery
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• v.8 no.4 s.31
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• pp.27-38
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• 2005

The present study investigated the effect of relative position of the blade on blade surface heat transfer. The experiments were conducted in a low speed wind tunnel with a stationary annular turbine cascade. The test section has a single turbine stage composed of sixteen guide vanes and blades. The chord length of the blade is 150 mm and the mean tip clearance of the blade is $2.5\%$ of the blade chord. The Reynolds number based on blade inlet velocity and chord length is $1.5{\times}105$ and mean turbulence intensity is about $3\%$. To investigate the effect of relative position of blade, the blade at six different positions in a pitch was examined. For the detailed mass transfer measurements, a naphthalene sublimation technique was used. In general, complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as a laminar flow separation, relaminarization, flow acceleration, transition to turbulence and tip leakage vortices. The results show that the blade relative position affects those heat transfer characteristics because the distributions of incoming flow velocity and turbulence intensity are changed. Especially, the heat transfer pattern on the near-tip region is significantly affected by the relative position of the blade because the effect of tip leakage vortex is strongly dependent on the blade position. On the pressure side, the effect of blade position is not so significant as on the suction side surface although the position and the size of the separation bubble are changed.

• Analytical Science and Technology
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• v.25 no.3
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• pp.197-206
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• 2012

Ambers are composed of polymer molecules which contain aromatic moieties such as benzene, naphthalene, phenanthrene and anthracene. They emit fluorescence when irradiated with ultraviolet light, which was used for confirming an amber. The fluorescence of amber, however, tends to decrease as the surface of amber is weathered with light, heat, oxygen for a long time. In this study, the reliability of confirming amber with its fluorescence by measuring the changes of fluorescence after artificial aging. Aging factors were UV light (${\lambda}$=340 nm), oxygen with heat (100%, $90^{\circ}C$) and heat ($90^{\circ}C$) and aging time was for 5, 15, 30 and 60 days, respectively. In the excitation and emission spectra of amber, the intensity decreased and the maximal wavelength was shifted to longer wavelength with artificial aging time. Especially, there was a drastic decrease in the intensity of spectra to 1.7% of initial value after 60 days aging under oxygen with heat. Only in Colombian amber there showed an increase of fluorescence intensity for a certain aging time, which could be explained by the production of aromatic ring in the presence of light and heat. Conclusively, the fluorescence can be lessened by the natural weathering with light, heat and oxygen and it is not accurate to recognize amber just with UV irradiation method.

• Korean Journal of Food Science and Technology
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• v.46 no.2
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• pp.189-197
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• 2014

Onion juices were prepared by various heat treatments (at $105-120^{\circ}C$ for 4.5-5.5 h), from the onions cultivated with increasing numbers of sulfur applications (once for Sulfur-1, four times for Sulfur-4). As heat treatment intensity increased, the onion juices darkened (p<0.001), which adversely affected the sensory preference. In addition, increasing the heating temperature significantly increased the organic acid content of onion juices (p<0.001), and therefore, decreased pH (p<0.001). Heat intensity did not affect the thiosulfinate content of onion juices, suggesting that the rate of decomposition of thiosulfinate into low-molecular weight sulfur derivatives is similar over the temperature range of $105-120^{\circ}C$. Total flavonoids were higher in onion juices derived from Sulfur-4 than in Sulfur-1 onions, and increased with heat treatment intensity (p<0.001). These results indicated that heat-facilitated conversion of bound forms of flavonoids to their free forms increases the extractability of flavonoids from onions.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.4
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• pp.363-372
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• 2000

In order to overtake a quantitative analysis of effect of anthropogenic heat and different land-use on urban thermal environment numerical simulation of surface energy budget was carried out under typical summer synoptic condition. It is beneficial to understand surface temperature of complex urban surace. The different land-use types are classified of rice field farm fruit garden residential region forest water and swamp by using map scaled 1/25000 of Pusan metropolitan. The model predicts that maximum heat island intensity in the central part of Pusan is 7$^{\circ}C$ at 2000 LST in summertime. The surface temperature is propotional to the density of constructions. The effect of anthropogenic heat generation on surface temperature is the increase of 0.3$^{\circ}C$ at 1400LST in the central part of Pusan during summertime.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.42-47
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• 2001

The heat (mass) transfer characteristics on the blade surface of a first-stage turbine rotor cascade for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is successfully developed for the measurements of the local heat (mass) transfer coefficient on the curved blade surface. The experiment is carried out at the free-stream Reynolds number and turbulence intensity of $2.09\times10^5$ and 1.2%. The results on the blade surfaces show that the local heat (mass) transfer on the suction surface is strongly influenced by the endwall vortices, but that on the pressure surface shows a nearly two-dimensional nature. The pressure surface has a more uniform distribution of heat load than the suction one.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1623-1629
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• 2003

In this paper, the arc beam is considered as a moving disc heat source with a pseudo-Gaussian distribution of heat intensity. The solution for temperature distribution on welds is derived by using the image heat source method and the superposition method. It is general solution in that it can determine the temperature-rise distribution in and around the arc beam heat source, as well as the width and depth of the melt pool (MP) and the heat-affected zone (HAZ) in welding short lengths, where quasi-stationary conditions may not have been established. As a comparative study, the results of this analytical approach has been compared with that of the finite-element modeling. As a result, The theoretical analysis presented here has shown good consistency and is more time/cost-effective method compared with FEM.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.04a
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• pp.209-214
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• 2000

The catalytic heat exchanger, which integrates two functions of heat generation and heat exchange into one equipment, was designed and its characteristics were investigated by experiments. The surface of the fin tube was deposited with Pd catalyst. The conversion of the mixture in the catalytic heat exchanger was more significantly affected by the inlet velocity of the mixture than by the inlet temperature and equivalence ratio of the mixture. It was found that the catalytic surface area of the fin tubes should be sufficiently increased to make the combustion intensity of the catalytic heat exchanger as high as possible. Results showed that the fin tubes, placed in the triangularly staggered form, should be adjusted so that the mixture flows uniformly over all the catalytic fin surfaces.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1442-1446
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• 2004

The heat (mass) transfer characteristics on the blade surface of a first-stage turbine rotor cascade has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is employed for the measurements of the local heat (mass) transfer coefficient on the curved blade surface. The experiments are carried out for two free-stream turbulence intensities of 1.2% and 14.7%. The high free-stream turbulence results in more uniform distributions of heat load on the both pressure and suction surfaces and in an early boundary-layer separation on the suction surface. The heat (mass) transfer enhancement on the suction surface due to the endwall vortices is found to be relatively small under the high free-stream turbulence.