• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.506-513
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• 2021

The use of fossil fuels is a major contributor to the increase atmospheric greenhouse gas emissions. As such problems arise, interest in new and renewable energy devices, particularly fuel cells, is greatly increasing. In this study, various characteristics of mixed strains were observed in wastewater collected by the Jeonju Environment Office to investigate the effects of microorganisms on voltage generation and voltage generation of substrates, electrode materials, electrons, electron transport media, and ash microbial fuel cells. As a result of separately measuring the voltage generated during inoculation, the inoculation voltage of Escherichia coli K12 (E. coli K12) was 0.45 V, and the maximum inoculation voltage of the mixed strain was 1.2 V. Thereafter, voltage values were collected using a digital multimeter and the amount of voltage generated over time was measured. In the case of E. coli K12, the maximum voltage reached 0.45 V, and the cell voltage was maintained above 0.23 V for 140 hours. In contrast, for the mixed strain, the maximum voltage reached 1.2 V and the voltage was slowly decreased to 0.97 V. In addition, the degree of microbial adsorption to the electrod surface after the inoculation test was confirmed using a scanning electron microscope. Therefore, these results showed the possibility of purifying pollutants at the same time as power generation through the production of hydrogen ions using microorganisms and wastewater.

• 한국초전도ㆍ저온공학회논문지
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• 제24권3호
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• pp.62-67
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• 2022

Liquid hydrogen (LH₂) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH₂ supply system is needed. In the high-pressure hydrogen station based on LH₂ currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.

• 해양환경안전학회지
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• 제28권2호
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• pp.361-369
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• 2022

강화되는 환경규제에 대응하기 위해서 세계 각국이 수소 경제로의 전환을 본격화하고 있으며, 이에 중장기적으로 수소의 국가간 물동량도 증가할 것으로 예상된다. 국가간 수소의 거래는 수출국의 신재생 에너지 자원과 수입국의 수소 사용 형태, 기술 성숙도 등을 고려하여 암모니아, 액화수소, LOHC 등의 형태로 이루어질 것이나, 어느 한 가지 형태로만 거래되지는 않을 것이다. 액화수소 대비 암모니아와 LOHC의 해상운송은 상대적으로 성숙한 기술임에 본 글에서는 향후 액화수소 운반선 개발을 위하여 필요한 세부 기술들의 식별 및 다양한 기술적 대안들을 통해 가능한 설계안을 확보하면서, 그에 따른 기술적 타당성을 분석하였다.

• 한국건설순환자원학회논문집
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• 제10권1호
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• pp.48-55
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• 2022

본 연구는 콘크리트의 운반 과정 중 발생하는 레미콘 회수수의 재활용율 증대 및 온실가스 저감을 위한 연구의 일환으로 회수수를 배합수 및 인공경량골재 프리웨팅수로 사용하고 고로슬래그 미분말 및 플라이애시를 시멘트 대체재로 사용한 3성분계 경량 골재 모르타르의 공학적 특성을 검토하였다. 이를 위해 3성분계 경량 골재 모르타르의 플로우, 기건단위질량, 압축강도, 건조수축, 중성화 깊이, 염화물 이온 침투 저항성을 측정하였으며 측정 결과 회수수를 사용할 경우 높아진 알칼리도에 의해 시멘트계 재료들의 반응성이 높아졌으며 3성분계 배합과 함께 사용할 경우 고로슬래그 미분말 15 %, 플라이애시를 5 % 사용할 시 모르타르의 압축강도 및 내구특성 향상에 긍정적인 것으로 나타났다.

• Applied Microscopy
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• 제52권
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• pp.5.1-5.10
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• 2022

The use of Pipelines for long-distance transportation of crude oil, natural gas and similar applications is increasing and has pivotal importance in recent times. High specific strength plays a crucial role in improving transport efficiency through increased pressure and improved laying efficiency through reduced diameter and weight of line pipes. TRIP-based high-strength and high-ductility alloys comprise a mixture of ferrite, bainite, and retained austenite that provide excellent mechanical properties such as dimensional stability, fatigue strength, and impact toughness. This study performs microstructure analysis using both Nital etching and LePera etching methods. At the time of Nital etching, it is difficult to distinctly observe second phase. However, using LePera etching conditions it is possible to distinctly measure the M/A phase and ferrite matrix. The fraction measurement was done using OM and SEM images which give similar results for the average volume fraction of the phases. Although it is possible to distinguish the M/A phase from the SEM image of the sample subjected to LePera etching. However, using Nital etching is nearly impossible. Nital etching is good at specific phase analysis than LePera etching when using SEM images.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.761-768
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• 2022

In the hope of realizing carbon neutrality, Korea has established the goal of expanding the supply of hydrogen electric vehicles through a roadmap to revitalize the hydrogen economy. A prerequisite for successful supply expansion is securing the safety of hydrogen electric vehicles. Certain parts, such as the hydrogen transport pipe and tank, in hydrogen electric vehicles are exposed to high-pressure hydrogen gas over long periods of time, so the hydrogen enters the grain boundary of material, resulting in a degradation of the parts referred to as hydrogen embrittlement. In addition, since the safety of parts utilizing hydrogen varies depending on the type of material used and its environmental characteristics, the necessity for the enactment of a hydrogen embrittlement regulation has emerged and is still being discussed as a Global Technical Regulation (GTR). In this paper, we analyze a hydrogen compatibility material evaluation method discussed in GTR and present a direction for the development of Korean-type hydrogen compatibility material evaluation methods.

• 한국산업융합학회 논문집
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• 제26권3호
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• pp.499-507
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• 2023

The core of the liquefied natural gas (LNG) carrier cargo containment system (CCS) is to store and transport LNG safely under temperatures below -163 degrees Celsius. The secondary barrier of the LNG CCS is adopted to prevent LNG leakage from CCS to the ship's hull structure. Recently, as the size of the LNG CCS increases, various studies have been conducted on the applied temperature and load ranges. The present study investigates the working condition-dependent bonding strength of the PU15 adhesives of the secondary barrier. In addition, the mechanical performance is analyzed at a cryogenic temperature of -170 degrees Celsius, and the failure surface and failure mode are investigated depending on the working condition of the bonded process. Even though the RSB and FSB-based fracture mode was confirmed, the results showed that all the tested scenarios satisfied the minimum requirement of the regulation.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.100-112
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• 2023

This study evaluated the contribution of carbon neutrality by calculating the carbon reduction amount and reduction intensity targeting the hydrogen pilot city and applying it to the carbon neutral reduction target. In the building sector, the reduction amount for 2030 was 10.8% on average. In addition, by 2050, the contribution to carbon neutrality of plan A was 14.1% on average, and the contribution to carbon neutrality of plan B was 15.1% on average. In the 2030 reduction amount of the transportation sector, the contribution to carbon neutrality was 138.4% on average. In addition, by 2050, the contribution to carbon neutrality in plan A was 82.5% on average, and the contribution to carbon neutrality in plan B was 74.9%. From the above research results, additional carbon reduction is possible when creating a hydrogen city, so it will be used as a basis of city-level carbon neutral model. It will also be used as a basis for technology development and investment promotion for various hydrogen supply methods in the future.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1280-1286
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• 2023

MgF₂ as a moderator material has been extensively used in the beam shaping assembly (BSA) that plays an important role in the boron neutron capture therapy (BNCT). Regarded as important for applications, the thermal neutron scattering data of MgF₂ were calculated, based on the phonon expansion model. The structural properties of MgF₂ were researched by the VASP code based on the ab-initio methods. The PHONOPY code was employed to calculate the phonon density of states. Furthermore, the NJOY code was used to calculate the thermal neutron scattering data of MgF₂. The calculated inelastic cross sections plus absorption cross sections are in agreement with the available experimental data. The neutron transport in the BSA has been simulated by using a hybrid Monte-Carlo-Deterministic code NECP-MCX. The results indicated that compared with the calculation of the free gas model, the thermal neutron flux and epithermal neutron flux at the BSA exit port calculated by using the thermal neutron scattering data of MgF₂ were reduced by 27.7% and 8.2%, respectively.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.49-55
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• 2023

This paper presents the design of a re-liquefaction system as a BOG (boil-off gas) handling process in liquid hydrogen transport vessels. The total capacity of the re-liquefaction system was assumed to be 3 ton/day, with a BOR (boil-off rate) of 0.2 %/day inside the cargo. The re-liquefaction cycle was devised using the He-Brayton Cycle, incorporating considerations of BOG capacity and operational stability. The primary components of the system, such as compressors, expanders, and heat exchangers, were selected to meet domestically available specifications. Case studies were conducted based on the specifications of the components to determine the optimal design parameters for the re-liquefaction system. This encompassed variables such as helium mass flow rate, the number of compressors, compressor inlet pressure and compression ratio, as well as the quantity and composition of expanders. Additionally, an analysis of exergy destruction and exergy efficiency was carried out for the components within the system. Remarkably, while previous design studies of BOG re-liquefaction systems for liquid hydrogen vessels were confined to theoretical and analytical realms, this research distinguishes itself by accounting for practical implementation through equipment and system design.