• 설비공학논문집
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• 제18권12호
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• pp.971-976
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• 2006

The objectives of this paper are to study the characteristics of pool boiling heat transfer for enhanced tubes used in the evaporator of turbo chiller and to provide a guideline for optimum design of an evaporator using HFC134a. Three different enhanced tubes are tested at 4 different saturation temperatures. The wall super heated temperature difference ranges from $0.5^{\circ}C\;to\;3.5^{\circ}C$. The refrigerant, HFC134a evaporates on the outside of the tube while the chilled water flows inside the tube. This study provides experimental heat transfer coefficients for evaporation on the enhanced tubes. It is found that the turbo-II tube provides the highest heat transfer coefficient.

• Nuclear Engineering and Technology
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• 제26권2호
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• pp.237-246
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• 1994

KMRR 노심의 열수력 설계 및 안전 해석을 위한 고유량 CHF 상관식을 개발하였다. 상관식 개발에는 fin이 부착된 경우와 부착되지 않은 경우의 가열봉에 대한 단일봉 CHF 실험 자료를 사용하였다. 상관식은 Reynolds 수, 열역학 평형 건도, 액상과 기상의 밀도비 및 등가수력 직경비 등의 무차원 변수로 이루어져 있으며, fin이 있는 경우와 없는 경우의 가열 둘레비를 사용하여 fin의 영향을 고려하였다. 이처럼 단일봉에 대하여 개발된 상관식의 KMRR 핵연료 집합체에 대한 적용 타당성을 보이기 위하여 비가열면 및 축방향 비균일 출력 분포의 영향을 논의하였다. CHF 실험 자료 분석 결과, 상관식 한계 DNBR은 1.44로 결정되었다.

• Korean Chemical Engineering Research
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• 제49권4호
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• pp.491-497
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• 2011

본 연구에서는 CO, $H_2$가 주성분인 모사합성가스를 이용하여 합성천연가스(SNG, Synthetic Natural Gas) 제조공정을 평가하기 위하여, 3종류의 SNG 합성반응시스템을 제안하였다. 제시된 공정은 다단 단열반응시스템, 재순환이 있는 다단 단열반응시스템 그리고 강제냉각방식의 수냉각반응시스템이다. 3개의 연속된 반응기로 구성된 다단 단열반응시스템에서의 1차반응기에서는 온도가 최대 $800^{\circ}C$까지 상승하였으며, 이로 인한 수성가스전환반응으로 인해 $CO_2$가 다른 시스템에 비해 많이 생성되었으며, SNG 내의 $CH_4$ 농도는 90.1% 정도를 얻었다. 다단 단열반응시스템의 문제점을 해결하기 위해 재순환이 있는 다단 단열반응시스템에서는 반응기의 온도제어를 위해 일부 전환가스를 재순환한 것으로, $CH_4$는 최대 96.3%를 얻었다. 이러한 다수개의 반응기로 구성된 단열반응기의 단점을 해결하여 반응기 개수를 줄일 수 있는 쉘과 튜브 형태의 반응기로 구성된 강제냉각방식의 수냉각시스템에서는 쉘 측으로 냉각수를 공급하여 반응열을 흡수하는 형태로, 공급되는 냉각수의 유량과 압력에 의해 온도를 제어할 수 있다. 이 시스템에서는 최대 $CH_4$는 최대 99.2%를 얻었으며, 1차 반응기인 강제냉각방식의 수냉각반응기 출구에서의 97% 이상의 $CH_4$ 농도를 얻을 수 있음을 확인하였다.

• 대한기계학회논문집
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• 제19권6호
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• pp.1518-1528
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• 1995

The deformation and departure processes of a bubble attached to the wall are studied experimentally and numerically to understand the phenomena of the nucleate boiling heat transfer enhancement under DC electric field. An air-bubble is injected in a dielectric liquid with different electric fields generated by changing three types of electrode system (Type 1,2 and 3) in the bubble generator. Experimental variables are the electric field strength and the distance and the shape of the electrodes under DC electric field. From experimental results, it is observed that the bubble under Dc electric field is elongated in the same direction as the electric field and the contact angle increases. For the parallel plate electrode which generates a uniform electric field, bubble departure volume doesn't seem to decrease within our experimental range. However, when a needle is raised a few millimeters from the lower electrode to make a nonuniform electric field around the needle, bubble departure volume decreases continuously with the increase of an applied voltage. The reduction effect of bubble departure volume is the most effective under a strong nonuniform electric field generated with Type 3. As the nonuniformity of the electric field due to the shape of a electrode increases, the terminal velocity and the acceleration of a bubble increase largely. For the comparison with visualization results, the deformation of a bubble attached to the electrode is carried out by a numerical method. Numerical results show good agreement qualitatively with experimental results.

• 한국염색가공학회지
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• 제6권2호
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• pp.55-62
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• 1994

The mend for fabric products has been increased remarkably with increasing population, housings, mutistory buildings,...and etc. during the last two decades. However, since fabrics are highly combustible and can produce toxic gases during the combution, fabric products can result in serious human injury as well as financial damage. Acknowledged by this, a new phosphorus based flame retardant suitable for PET fabric has been synthesized by making use of the reaction of diphenyl chloro phosphate and hexamethylenediamine. Since the starting meterials are relatively cheap and the yield of this reaction is high (more than 90%), this reaction seems to be very effective as wall as very economic. By analyzing various spectrophotometric analysis data such as NMR, FT-IR, and Mass, this new flame retardant is identified to be N,N’-Bis(diphenyl chlorophosphoro)diamino hexane. In the mean time, DSC measurement has shown that the melting point and the boiling point of this material are around 115$^{\circ}C$ and around 40$0^{\circ}C$, respectively. The flame retardancy test done on the PET fabric processed by this flame retardant have shown excellent in times of flame contact, times of flame contact for washable. The most economical finishing condition estimated 10% in concentration of BDPDH, Moreover, it has been also found that the drape stiffness of the PET fiber processed by the flame retartant is changed very litter compared to the unprocessed original PET fabrics. Judging from this, the potential of this new phosphrdus based compond as a flame retardant for PET fabric seems to be high.

• 자원환경지질
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• 제31권1호
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• pp.1-10
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• 1998

Copper mineralization of the Donghwa and Hwanghagsan mines was deposited in hydrothermal quartz veins which filled fissures in Cretacous sedimentary rocks. Ore minerals are pyrite, sphalerite, chalcopyrite, bornite, galena, wittichenite and unidentified Cu-Bi-Pb-Sb-S mineral. On the basis of salinities and homogenization temperatures for fluid inclusions, the Donghwa deposit was deposited from $300^{\circ}C$ to $220^{\circ}C$ with 2.5 to 0.2 wt.% eq. NaCl, and the Hwanghagsan deposits was deposited from $300^{\circ}C$ to $160^{\circ}C$ with 4.0 to 0.0 wt.% eq. NaCl. Evidence of boiling suggests pressure of 170 to 60 bar, these pressures correspond to 1700 m to 600 m. The ${\delta}^{34}S_{H_2S}$ values of the Donghwa deposit (4.8~7.4%) are higher than those of the Hwanghagsan deposit (3.5~4.5%), sulfur isotope compositions indicate that ore fluids partially reacted with meteoric water and wall-rock. Equilibrium thermodynamic interpretation indicates that the temperature versus $fs_2$ of the Donghwa deposit (> $420^{\circ}C$, $10^{-3.2}atm$) is higher condition than that of the Hwanghagsan deposit (> $290^{\circ}C$, $10^{-7.0}atm$). K-Ar ages for biotite granite and quartz porphyry in the study area are 64.7 Ma, and 60.9 Ma, reapectively. Mineralization age using sericite in the Donghwa deposits is 59.8 Ma. Therfore, Copper mineralization in the study area was associated with acidic igneous activity such as biotite granite or quartz porphyry.

• 한국가스학회지
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• 제2권4호
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• pp.53-59
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• 1998

기-액 2상유동장에서 유동양식은 압력강하, 보이드율분포, 유동장의 기하학적 형상과 밀접한 관계가 있다. 한편 원유수송, 비등이 발생하는 유동, 펌프에서 발생하는 케비테션 현상, 그리고 화학 반응로와 같은 상변화 장치 등의 2상유동에서 고분자물질에 의한 저항감소 현상의 적용이 가능할 것으로 예상된다. 그러나 2상유동장에서 고분자물질에 의한 저항감소에 관한 연구는 매우 미비하다. 그래서 본 연구는 2상유동장에 합성고분자물질(A611p)에 의한 저항감 소율을 실험을 통하여 계측 및 분석하였다. 본 연구에서는 고분자물질의 농도를 증가시킬수록 국부보이드율의 최고치가 관의 중심에서 관의 벽쪽으로 이동하며 2상유동의 유동양식이 변화됨을 규명하였다. 그래서 저항감소율과 유동양식과 밀접한 관계가 있음을 예측할 수 있었다.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1318-1326
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• 2001

The evaporation heat transfer coefficient and pressure drop for refrigerant R-22 flowing in the plate and shell heat exchanger were investigated experimentally in this study. Two vertical counterflow channels were farmed in the exchanger by three plates of commercial geometry with a corrugated trapezoid shape of a chevron angel of 45 ° Upflow boiling of refrigerant R-22 in one channel receives heat from the hot downf1ow of water in the other channel. The effects of the mean vapor quality, mass flux, heat flux and pressure of R-22 on the evaporation heat transfer and pressure drop were explored. The quality change of R-22 between the inlet and outlet of the refrigerant channel ranges from 0.03 to 0.05. The present data showed that both the evaporation heat transfer coefficient and pressure drop increase with the vapor quality. At a higher mass flux, the evaporation heat transfer coefficient and pressure drop are higher for the entire range of the vapor quality Raising the imposed wall heat flux was found to slightly improve the heat transfer, while at a higher refrigerant pressure, both the heat transfer and pressure drop are slightly lower.

• 자원환경지질
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• 제27권4호
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• pp.335-343
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• 1994

The Eonyang amethyst deposits are composed of vug quartz emplaced in the Eonyang granites of Mesozoic Cretaceous age. The Eonyang granites are composed of biotite granite, porphyritic biotite granite, aplite and miarolitic granite. The petrochemical data of the Eonyang granites show the trend of subalkaline magma, calc-alkaline magma, I-type granitoid and magnetite series. The vug quartz show the characteristic growth zoning (white quartz-smoky quartz-amethyst) from wall side. Generally fluid inclusions in the vug quartz can be divided into four main types based on compositions (I-type: gas inclusion, II-type: liquid inclusion, III-type: polyphase inclusion, IV-type: liquid $CO_2$-bearing inclusion). Solid phase of polyphase inclusions are halite(NaCl), sylvite(KCl), hematite ($Fe_2O_3$) and unknown anisotropic solid. Homogenization temperatures inferred from the fluid inclusion study ranges from $440^{\circ}C$ to $485^{\circ}C$ in white quartz, from $227^{\circ}C$ to $384^{\circ}C$ in smoky quartz, from $133^{\circ}C$ to $186^{\circ}C$ in amethyst, respectively. Salinities of fluid inclusions in each mineralization stages ranges from 40 wt.% to 58 wt.% in white and smoky quartz, from 1.0 wt.% to 8.7 wt.% in amethyst respectively. A consideration of the pressure regime during vug quartz deposition based on the boiling evidence suggests lithostatic pressure of less than 72 bars. This range of pressure indicate that vug quartz lay at depth of 750 m below the surface at the during mineralization.

• 한국방재안전학회논문집
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• 제10권1호
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• pp.11-17
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• 2017

본 연구에서는 지반굴착공사로 인해 발생된 지반함몰 사례를 분석하고 지반함몰 발생 원인을 평가하였는데, 주요 원인으로는 지반조사의 불충분, 부정확한 지반정수, 가시설 보조공법 구조체의 결함, 보일링 및 히빙에 대한 대처 미흡, 시공시 과굴착 등으로 나타났다. 그리고 지반함몰 발생원인 분석을 통해 지반굴착공사 위험요소를 도출하였는데, 지반조사, 굴착공법 선정, 구조물 해석, 계측계획, 굴착공법 시공, 지하수위 변화, 계측 수행, 자연재해, 시공관리 등이 지반함몰을 예방하기 위해 고려해야할 위험요소로 도출되었다. 또한, 도출된 위험요소에 대한 중요도를 평가하고, 신뢰도를 높이기 위해 국내 전문가들을 대상으로 설문조사를 수행하였고, 카이제곱(${\chi}^2$) 검정 방법 통해 설문조사 응답자의 직업군, 업무종사기간, 업무현장종류 등과 설문조사결과가 유의한 수준인지에 대해 검정을 수행하였다.