• 기계와재료
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• v.24 no.1
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• pp.64-71
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• 2012

열교환기은 대부분의 플랜트에서 공정효율을 결정하는 핵심기자재이다. 이에 따라 플랜트 전체 효율을 향상시키기 위한 고효율 열교환기에 대한 연구개발이 꾸준히 이루어지고 있으며, 최근 들어 심해저플랜트 등의 고압환경용, 가스액화 플랜트 등에 적용되는 극저온용, 가스터빈 등에 적용되는 초고온용 등 극한환경에서 사용되는 플랜트용 고신뢰용 열교환기에 대한 니즈가 증가하고 있다. 따라서, 국내업체들의 플랜트 기자재 시장 진입 및 점유율 확대를 위해 이러한 극한환경용 열교환기에 대한 원천기술 확보 전략이 필요하다. 이를 위해 본 연구에서는 플랜트용 열 교환기 기술현황에 대해 살펴보고자 한다.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.99-105
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• 2016

The present study has been carried out to analyze the flow characteristics with geometric shape and control conditions in subsea by-pass valve. The function of by-pass valve is to prevent reverse flow. In this study, the static analysis has been perform for analyzing fluid flow in open state. In order to consider the turbulent effect, the standard ${\kappa}-{\varepsilon}$ model was used. A variety of parametric studies, such as by-pass valve type or size, volume flow rate, leakage hole size, leakage hole position, block type, block shape, were performed. The pressure difference across the valve in the model broadened the flow channel cross-sectional area was greater than the base model for the same operating conditions. As the pipe diameter in the block decreases the pressure difference is greatly increased. The pressure difference according to block shape such as edge type and round was almost negligible. For the same Reynolds number the pressure difference was little changed according to the size of the valve.

• Ocean and Polar Research
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• v.26 no.2
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• pp.311-321
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• 2004

Relationships between sedimentary environments and abundance of benthic animals were examined on the deep-sea floor, the Clarion-Clipperton Fracture Zone, in the northeast equatorial Pacific Ocean. Specimens were collected using a box corer at 8 stations by sieving through 0.3 mm mesh screen. Sediments showed finer grain size ranged from 5.63 to $7.97{\varphi}$, 83.1% of mean porosity, 1.81 kPa of mean shear strength and organic carbon content in sediment ranged from 0.97 to $1.87\;mg/cm^3$. Manganese nodules covered on the bottom layer from 4 to 57% of coverages. A total of 26 faunal groups in 6 phyla was sampled and comprised 1,467 individuals. Mean biomass were calibrated to 0.5 gWWt/$0.06\;m^2$. Small-sized animals including foraminiferans and nematods were dominated among the faunal group which comprised 49.1% (892 ind.) and 11.5% (320 ind.), respectively. In SPI-analysis, vertical bio-disturbance marks were not observed except to Beggiatoa-type bacterial mats. As the results of relationship between environments and benthos, abundance of benthic animals, especially nematode, showed only a negative correlation to the coverage of nodules, and any other sedimentary factors analyzed in this study were rarely affected to the spatial distribution of benthic animals.

• Ocean and Polar Research
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• v.26 no.2
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• pp.255-263
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• 2004

This study was conducted to investigate the community structure and distributional pattern of meiobenthos in the deep-sea bottom of the Clarion-Clipperton Fracture Zone of the northeastern Pacific during July 2003. The samples were collected using the multiple corer at 13 stations along the transects fiom $5^{\circ}N\;to\;17^{\circ}N$. The most abundant meiobenthos was nematodes and followed by sarcomastigophorans; these two taxa comprised more than 70% of the total abundance at all stations. For size distribution analyses showed that animals which fit into the sieve mesh size of 0.063mm were abundant. The maximum density of meiobenthos was $147inds./10cm^2$ at station located in $7^{\circ}N$, and the minimum density was $6 inds./10cm^2$ at station located in $14^{\circ}N$. More than 60% of meiobenthos were distributed at surface sediment layer within 1.0cm, and the peak abundance was found at $0{\sim}0.25cm$ layer. The latitudinal distribution pattern of meiobenthos in the study area seemed to be related with the primary productivity of the surface water that is also connected to the water circulation pattern of the Pacific Ocean near the Equator, diverging at latitude of $8^{\circ}N$ and conversing at $5^{\circ}N$.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.311-320
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• 2006

Digital filters designed using wavelet theory are applied to bathymetry data acquired from KR5 area of Korea Deepsea Mining Area. The filters used in this study are the linear B-spline wavelet filter and derivative of a Cubic B-spline filter. With proper tuning of the digital filters, we can identify the location and orientation of the abyssal hill and abyssal trough in bathymetry. These features obtained from the digital filters are well correlated with bathymetric image. This quantitative information, which can be used to understand the underlying geophysical processes, can be further processed to obtain the spacing, orientation and distribution of the abyssal hill. This wavelet analysis of bathymetry provides good data to select the mining site.

• Ocean and Polar Research
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• v.25 no.4
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• pp.529-543
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• 2003

Deep-sea surface sediments, acquired from 1997 to 2002 in the Clarion-Clipperton fracture zone of the northeast equatorial Pacific, were analyzed for index and geotechnical properties to provide background information for the design of manganese nodule minor. The sediments were classified into 16 types based on the measured properties and evaluated in terms of miner maneuverabillity and potential environmental impacts arising from mining activities. It was found that the middle part of the study area covered with coarse siliceous sediments is more favorable to the commercial production than the northern part of pelagic red clay. In particular, Area B2 in the middle part is considered the best mining site since it shows the highest abundance as well as it consists mostly of normally to over consolidated (types B, C, D) coarse siliceous sediments that are appropriate for effective minor movement and accompany weak environmental impacts. Taking account of all the analyzed core logs, the average shear-strength values are proposed as a practical guideline fur movements of a manganese nodule miner: 6.0 kPa at 10cm and 7.0kPa at 40cm below the seabed.

• Tunnel and Underground Space
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• v.25 no.2
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• pp.133-143
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• 2015

Gas hydrate is a solid substance composed of natural gas constrained in water molecules under low temperature and high pressure conditions. The existence of hydrates has been reported to be world-widely distributed, mainly at permafrost and deep ocean floor. Test productions of small amount of natural gas from the on-shore permafrost have been accomplished in U.S.A and Canada, but, world-first and the only production case from off-shore hydrate bearing sediments was in Nankai trough, Japan. In this study, we introduce key technologies in gas production from hydrates by analyzing the Japanese off-shore gas production project in Nankai trough in terms of depressurization- induced dissociation so as to utilize planned domestic gas production test in Ulleung basin.

• 한국해양학회지
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• v.30 no.4
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• pp.365-370
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• 1995

A new piston-type Free-fall corer (FFC) was developed for the sampling of core sediments in aquatic environments. The corer, named "KORDI-FFC", is the modified sampler of the existing FFX with an open barrel gravity corer. It was rested successfully on the muddy bottom in the Chinhae Bay and on the sandy bottom (Mz=3$\phi$) in nearshore areas around the Cheju Island. Several merits found in the unstrument are; $\circled1$ operation on a small vessel without winch and cable, $\circled2$ low cost of construction, $\circled3$ little disturbance of surface sediments during the sampling, $\circled4$ short round-trip time of sampling, and $\circled5$ simultaneous performance of other research works during the lowering of FFC.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.1
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• pp.42-47
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• 1997

This study was carried out to investigate the faunal composition and distribution pattern of meiobenthic community in the deep sea sediments of northeastern Pacific Ocean. Faunal samples were collected at 10 stations using a multiple corer and a spade type box corer during May 1996. A total of 18 meiofaunal groups were found, and Sarcomastigophora was the most dominant group which accounted for 35.8% of total meiofaunal abundance. Nematoda (30.8%), Nauplius larvae of Crustacea (11.9%), Ciliophora (6.8%) and Harpacticoida (3.0%) which were also important components of the meiofaunal community. All of these five faunal groups comprised more than 90% of total meiofauna. The highest density of 195 ind./10 $cm^2$ was found at St. 4 (4960 m water depth), but the lowest one, 85 ind./10 $cm^2$ at St. 1 (4969 m water depth). The overall mean density of meiofauna was estimated as $1.34{\times}10^5\;ind./m^2$. The abundance of meiofauna showed a slow decreasing trend along the water depth. The highest density was observed in the upper 1 cm and density decreased drastically with increasing depth from the surface.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.526-534
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• 2016

This study had the goal of designing onboard structures for a pre-pilot mining test (PPMT), which is required for the commercialization of the deep-sea mining industry. This PPMT is planned to validate the performance of a hydraulic lifting system and verify the concept of operating through a moon-pool in the east sea, Korea. All of the onboard equipment and facility were designed by KRISO. Because the test was performed at the first development, it is difficult to determine what risk will occur in the facility. Therefore, risk-based design is required in the facility for the PPMT, which includes the facility layout, failure mode and effect analysis (FMEA), and risk reduction plan. All of the expected performances of the lifting system itself and the onboard facilities were qualitatively validated using the risk-based design.