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This study proposes the integrated designs of energy systems and a re-liquefaction system for ocean-going LH2 tankers. Five prospective energy systems (Systems A to E) are suggested, using LNG as fuel, and a re-liquefaction system with a Claude cycle is developed. Their economic value, technological feasibility, and environmental impact are evaluated. The re-liquefaction systems' exergy efficiency and specific energy consumption ranges were 26.79–46.27% and 3–7.45 kWh/kg, respectively. The re-liquefaction system in System C is economically feasible up to $2/kg of H2. LCC of the integrated designs shows that System C has the lowest cost of $140 million. The shipping costs for each design are reviewed, and the lowest one is $447/ton of H2 for System C. Although System C CAPEX is the second expensive, it has the highest efficiency. Consequently, System C with the low-pressure engine, SOFC, and the re-liquefaction system is determined to be the optimal one.

This paper presents an operation scenario-based design methodology to determine the design pressure of the storage system of liquid hydrogen (LH2) import terminals. The methodology includes operation scenario establishment, thermodynamic analysis, and structural analysis. In a case study conducted, the terminal has a storage capacity of 75,000 m3, imports cargo from a 50,000 m3 LH2 tanker, and supplies hydrogen in vapor and liquid forms without any loss of boil-off hydrogen (BOH) as a reference case. In the deviation from the reference case, 4.7% of the entire imported LH2 needs proper treatment as BOH under the application of a non-pressurized storage system. In addition, the vapor pressure of the imported LH2 is the most influential in determining the design pressure. From the obtained design pressure, the structural analysis is performed in compliance with the Boiler & Pressure Vessel Code of American Society of Mechanical Engineers.

Owing to increasing demands for clean energy, caused by global warming, renewable energy sources have attracted significant attention. However, these sources can affect the reliability of electrical grids owing to their intermittency. Power-to-gas technology is expected to help address this issue. In this study, the CO2 methanation process, which yields synthetic natural gas (SNG) via the synthesis of CO2 and H2 through proton exchange membrane (PEM) water electrolysis using surplus electricity generated from renewable energy, was evaluated and optimized based on techno-economic analyses. Requirements for the introduction of SNG produced through CO2 methanation in domestic natural gas markets are presented by considering various scenarios. Results indicate that, even if the electricity costs, including system marginal price and renewable energy costs, are minimal, the costs for PEM water electrolysis and CO2 methanation must be reduced by ~$550/kW and 25%, respectively, relative to current levels for the viable introduction of SNG in domestic markets.

This study analyzes the thermodynamic, economic, and regulatory aspects of boil-off hydrogen (BOH) in liquid hydrogen (LH2) carriers that can be re-liquefied using a proposed re-liquefaction system or used as fuel in a fuel cell stack. Five LH2 carriers sailing between two designated ports are considered in a case study. The specific energy consumption of the proposed re-liquefaction system varies from 8.22 to 10.80 kWh/kg as the re-liquefaction-to-generation fraction (R/G fraction) is varied. The economic evaluation results show that the cost of re-liquefaction decreases as the re-liquefied flow rate increases and converges to 1.5 $/kg at an adequately large flow rate. Three energy efficient design index (EEDI) candidates are proposed to determine feasible R/G fractions: an EEDI equivalent to that of LNG carriers, an EEDI that considers the energy density of LH2, and no EEDI restrictions. The first EEDI candidate is so strict that the majority of the BOH should be used as fuel. In the case of the second EEDI candidate, the permittable R/G fraction is between 25% and 33%. If the EEDI is not applied for LH2 carriers, as in the third candidate, the specific life-cycle cost decreases to 67% compared with the first EEDI regulation.

This study proposes a new methodology of exergy-based economic analysis incorporating safety investment cost (SIC) for the comparative evaluation of process design alternatives for plants in terms of efficiency and economics while considering safety. Exergy-based economic analysis is employed to synthetically evaluate the design factors within the same framework. The SIC is estimated as the cost required to ensure the safety of the design by reducing accident risks to a level that is ‘as low as reasonably practicable’ (ALARP), which presents a rational approach to converting the risks associated with design alternatives into monetary values for economic analysis. The proposed method is applied to select the optimal working fluid in the Rankine cycle used in the recovery of both waste heat from a gas turbine and cold energy from liquefied natural gas (LNG) of the regasification process. The Rankine cycle, using ammonia, propane, and carbon dioxide as the working fluid, produces electric power of 11.7 MW, 8.9 MW, and 7.4 MW with specific exergy costs of 45.0 $/GJ, 61.9 $/GJ, and 77.8 $/GJ, respectively. Ammonia can be selected as the best alternative. The results are limited to quantitative risk assessment that does not consider domino effect and environmental damage.

Based on the existing structural and system reliability analysis methods, structural availability was recently proposed for the yield strength of beam elements subjected to external random loads. Structural availability has the potential to deal with the features of operation and the maintenance of structures, as well as structural integrity, in a quantitative manner. This paper reports another investigation on structural availability following previous research. Among the two different themes of this study, one is the structural availability estimation on the buckling strength of beams using the same method that was previously proposed for yield strength, and the other is to formulate a general failure model that covers structural deterioration over time and then to compute the structural availability based on the failure model by means of a numerical method, such as Monte Carlo simulation. Relevant examples are also included in this article. This study is expected to help further understand the feasibility of structural availability application in the actual design process and the risk-based design of structures.

Hydrogen energy can be effectively converted from various energy sources, such as renewable energy or hydrocarbon fuel, and therefore, it is a promising energy source. Various hydrogen production processes have been proposed worldwide because conventional energy conversion systems, after minor design modifications, can be used for such conversions. However, hydrogen gas can be more dangerous than other flammable gases if released into the atmosphere, where it can rapidly reach its explosion limit because of its high diffusion velocity. Therefore, a failure mode and effects analysis (FMEA) for hydrogen production processes is required. In this study, FMEA is performed for hydrogen produced from coal syngas using Thermococcus onnurineus NA1, which was discovered in the Indonesian deep sea. A fuzzy inference methodology is introduced for a quantitative analysis of the linguistic ambiguity of risk priority number estimated from a conventional FMEA. To estimate the objective severity ranking, we introduced the potential asset loss combined with the proportionate cost of each piece of equipment under total capital investment and a weight value influenced by environmental and mankind. Moreover, we proposed a fuzzified risk matrix to effectively represent the fuzzy risk priority number (f-RPN) under the risk matrix; variation with and without fuzzification of risk priority number is then expressed to ascertain why this variation has occurred through a vector diagram. Based on the f-RPN vector diagram, we have performed a design revision of the hydrogen production process using Thermococcus onnurineus NA1 to adjust the risk priority number downward from a broadly unacceptable region.

This study proposed a decision procedure to determine an optimal set of component reliabilities to satisfy the system target reliability with a minimum investment. The relationships between the initial costs and reliability were studied for each structural component to establish an objective function. Finite element analysis and Monte Carlo simulations were performed in order to set the relationships. The system configuration and target reliability of the structural system were used as the inequality constraint of the optimization process to maintain its safety level. A pile-guide mooring system (PGMS), a new mooring concept for an offshore liquefied natural gas bunkering terminal, was considered as a case study. The PGMS was modeled as a series system combining k-out-of-n components to consider the redundant parts. Finally, the proposed method determined the optimal number of guide-piles, redundant parts, and an optimal combination of component target reliabilities for the PGMS.

With the development of renewable energy sources, large-scale energy storage has been studied such as advanced compressed air energy storage (CAES) and liquid air energy storage (LAES). In this study, a novel pressurized cryogenic air energy storage system (PCAES) is proposed and analyzed. The conventional LAES system produces and stores the liquid air at the ambient pressure. The system achieves 40% to 60% of round-trip efficiency depending on the use of liquid turbo-expander. Meanwhile, this proposed system stores the air near the critical point by expanding it at 40 bar using turbo-expander. This significantly reduces the energy input in comparison to liquefying the air. This system is modeled with commercial process simulation software, Aspen HYSYS v.8.8. It significantly improves the round-trip efficiency of the conventional stand-alone liquid air energy storage system. However, this system requires pressurized tanks for the supercritical air storage. The economic evaluation for energy storage cost should be analyzed depending on variables such as storage time, storage to generation power ratio, and size of the power system. The above-ground CAES, LAES, and the proposed system would be the competitive system without geological limitations and are potentially applicable for the various energy demand-supply environments and the markets.

This study investigates the safety integrity levels for an electric propulsion system based on a molten carbonate fuel cell in a liquefied hydrogen tanker. The electric propulsion system necessitates multiple electronic and electric elements; thus, the functional safety of the system should be considered. Additionally, a maritime fuel cell system is nonconventional propulsion machinery. This system should follow a risk-based ship design framework, and IEC 61511 is a suitable standard for evaluating the functional safety of the system. Hazardous operability studies provide basic information for determining the safety integrity. In this work, a safety layer matrix and calibrated risk graph are generated, and a layer of protection analysis is conducted for a molten carbonate fuel cell stack. Eight guidewords are used to describe accidental scenarios and compare the results of the three methods in an unbiased manner. The most severe consequences are fire and explosion caused by overflows or a control failure in the stack, and the safety integrity levels are mutually different.

This study presents an economic evaluation for comparing two systems designed to manage boil-off gas (BOG) and to take advantage of liquefied natural gas (LNG) cold energy in LNG import terminals. The first system, called a BOG recondensation system, directly uses LNG cold energy by mixing BOG and LNG in the recondenser. The product of the system is natural gas (NG) obtained from the regasification process, and its required electricity must be purchased from the wholesale market. The other system is a BOG-fueled gas turbine cycle combined with a Rankine cycle. This system produces both NG and electric power. The gas turbine cycle uses BOG as the fuel for generating power, and its flue gas provides heat for the Rankine cycle in which the working fluid is used to recover LNG cold energy and cool the turbine inlet air. An exergy-based economic evaluation and a profitability comparison are employed to separately estimate the costs of each product generated by the systems and synthetically compare the economical preference between the two systems, respectively. The unavailability of the system provides the influence of equipment failure on the economic evaluation by estimating the costs and loss of profit caused by the unavailability. The results show that the BOG-fueled gas turbine cycle combined with a Rankine cycle is a better option than the recondensation system.

Liquid air can be employed as a carrier of cold energy obtained from liquefied natural gas (LNG) and surplus electricity. This study evaluates the potential of liquid air as a distributed source with a supply chain for a cold storage system using liquid air. Energy storing and distributing processes are conceptually designed and evaluated considering both the thermodynamic and economic aspects. Further, the proposed supply chain is compared with a conventional NH3/CO2 cascade refrigeration system. The thermodynamic analysis demonstrates that the exergy efficiency and the coefficient of performance of the proposed supply chain are 22% and 0.56, respectively. Economic analysis is based on a life cycle cost (LCC) evaluation. From the economic analysis, the liquid air production cost and the LCC of a liquid air cold storage system (LACS) are estimated to be 40.4 USD/ton and 34.2 MMUSD, respectively. The LCC is reduced by 19% in the LACS compared with the conventional refrigeration system. The proposed supply chain is economically feasible, although its thermodynamic performances are lower than those of the conventional system. The sensitivity analysis indicates that LNG mass flow rate in the air liquefaction system and the cold storage operating time are dominant parameters affecting the economic performance.

This study investigates the proper configuration of an electric propulsion system for a very large ethane carrier. The system consists of a dual-fuel diesel electric generator and a solid oxide fuel cell-gas turbine hybrid system to replace the mechanical propulsion system based on a marine diesel engine. When the ship navigates the open sea, the dual-fuel diesel electric generator and hybrid system run in parallel at a power rating of 16 MW. However, the hybrid system only operates during the berthing state for ship hoteling. The system efficiency, energy efficiency design index, and availability are considered to identify the optimal system configuration. When the dual-fuel diesel electric generator produces 10 MW, the hybrid system generates 6 MW. Because the electric propulsion system complies with international environmental regulations, it may be broadly acceptable for gas carriers in terms of eco-efficiency. The system achieves high availability by using fault tree analysis and minimal cut sets.

This study investigates the thermodynamic behavior that occurs when cryogenic liquids, such as liquefied natural gas (LNG) and liquid hydrogen, are stored. The experiment was conducted with liquid nitrogen and cryogenic liquid under 0.024 W/(m K) using vacuum insulation characterized by a thermal conductivity coefficient similar to that of the polyurethane foam commonly installed in LNG storage tanks. The experimental conditions are found to be similar to those of a commonly used type-B (membrane type) LNG storage tank based on the calculations of the thermal aspect ratio, which indicates the heat ingress ratio from the sides of the tank compared to the total heat ingress. Cryogenic liquid stored in a tank generally shows different thermodynamic behaviors because of the heat ingress from the outside. Compared with those predicted by the homogeneous model, the experimental results indicate different behaviors because of thermal stratification. The results particularly show that thermal stratification is highly correlated with the thermal aspect ratio. Moreover, the higher-level fraction results in faster pressure increases, which is in contrast with the result predicted by the homogeneous model. The boil-off gas rate generated is significantly less than that predicted by the general calculation in the homogeneous model even if much boil-off gas is generated in the early stage in a system with a high-level fraction. In conclusion, this study shows that the thermodynamic behaviors resulting from thermal stratification are significantly different from those predicted by the homogeneous model. Therefore, the related equipment must be designed and operated based on these considerations.

This paper proposes an LNG fuel gas supply system in which the compressors are used for multiple purposes. Referred to as the compressor-assisted fuel gas supply system (CA-FGSS), the proposed system uses its compressors to both manage the boil-off gas (BOG) in the LNG fuel tank and generate a pressure differential for drawing LNG from the tank. The feasibility of the defined operation sequence of the CA-FGSS was verified by dynamic process simulations in which the system was applied to two-stroke dual-fuel engines that required medium and high fuel gas injection pressures (16 and 300 bar), respectively. An availability analysis revealed 99% system availability of the CA-FGSS, which has a lower number of redundant equipment compared to a conventional pump-based fuel gas supply system (PB-FGSS). This is because the CA-FGSS does not use components with high failure rates and long maintenance times, such as in-tank pumps in the LNG fuel tank. These findings demonstrate the economic feasibility of the CA-FGSS, which also has a 10% lower capital expenditure compared to a PB-FGSS. A sensitivity analysis of the entire propulsion system of the CA-FGSS further showed that it was operationally more economical than a PB-FGSS for the same gas supply pressure. Moreover, a high-pressure propulsion system that utilizes the CA-FGSS was found to be more economical than a medium-pressure propulsion system for a high LNG price.

This study evaluates the structural feasibility of a prismatic pressure vessel using strength assessments. A prismatic pressure vessel, which differs from a cylindrical or spherical pressure vessel, is proposed. A prismatic pressure vessel can be used to ship liquefied gas. A prototype of the prismatic pressure vessel was designed, manufactured and tested in accordance with the ASME Boiler and Pressure Vessel Code. Its design uses the “design-by-analysis” method, including protection against plastic collapse. The prototype of the prismatic pressure vessel uses typical construction materials considering their linear elastic and nonlinear plastic behaviors. The vulnerable components of the structure were obtained through numerical analysis using the finite element method. A pressure test with strain gauges was conducted, and the results demonstrate the feasibility of the prismatic pressure vessel as a suitable vessel for high-pressure fluids with high volume efficiencies. The prismatic pressure vessel has potential for general applicability in the shipping of liquefied gas.

This paper presents a methodology for estimating the minimum design vapor pressure of prismatic pressure vessels for on-ship application. Engineering authorities guide the codes for a novel concept design such as a prismatic pressure vessel using a design by analysis (DBA). DBA methods enable high efficiency because they directly calculate the loads to avoid inherent conservativeness that exists in a design by rule (DBR). However, in DBA methods, the designer should conduct a finite element analysis (FEA) and evaluate the results iteratively to meet the design criteria. In this paper, we propose a new approach to estimating the minimum vapor pressure of a prismatic pressure vessel that follows the design philosophy of an IMO Type C independent tank. The procedure of the proposed method was demonstrated based on a case study. An FEA was also conducted for verification purposes. The results show that the proposed method can effectively estimate the required minimum shell thickness and designed vapor pressure without conducting an iterative FEA. In addition, minimization of the tank shell thickness is made possible because the proposed method directly calculates the crack propagation rate to avoid an unnecessary margin while satisfying the fatigue crack propagation criteria.

The vapour-liquid condensation phenomenon in a pressure tank in a thermally stratified state was experimentally investigated. Vapour under designated conditions was injected into the pressure tank, which contained low-temperature test fluid (R290) in a saturated liquid state, for identification of the condensation phenomenon in the thermal stratification state. The vapour-liquid condensation phenomenon was qualitatively and quantitatively analysed by investigating the heat and mass transfer. The vapour injected was partially condensed, yielding a non-equilibrium state between the vapour and liquid inside the tank. Further, a temperature stratification phenomenon occurred between the upper and lower regions of the liquid. This non-equilibrium state constituted a different result to that for vapour-liquid condensation obtained through thermodynamic modelling assuming an equilibrium state. The factors affecting the vapour-liquid condensation phenomenon included the mass and initial pressure of the liquefied inventory in the test cell, along with the pressure, and flow rate of the inlet vapour flow. Thus, the vapour-liquid condensation phenomenon was experimentally clarified in this study by setting those factors as variables. Four sets of experiments were performed to confirm the effect of each variable. The higher the enthalpy of the inlet vapour flow, the faster the pressure rose. Further, a higher pressure corresponded to a lower energy requirement for condensation. A lower initial energy of the liquid region in the test cell corresponded to a faster condensation rate, and the liquid level fraction did not affect the condensation rate. Mathematical modelling predicted the pressure behaviour to within a 8% error.

This study proposes a pile-guided floater, a new mooring concept, for large offshore floating structures such as an offshore liquefied natural gas (LNG) bunkering terminal. The economic feasibility of the new mooring system was demonstrated through a cost–benefit analysis. The environmental loads acting on the floaters were computed using wave data at the target location. The mooring system was designed using finite element analysis to estimate the additional investment. An LNG ship-to-ship bunkering operation that included an LNG bunkering terminal, LNG carrier, LNG bunkering shuttle, and LNG receiving ship was adopted. To estimate the technical feasibility and economic benefit of the proposed mooring system, the availabilities of two types of LNG bunkering terminals were compared considering the acceptance criteria for LNG ship-to-ship transfers. One LNG bunkering terminal was a typical barge-type floater and the other was the pile-guided floater. The relative motion of the terminal with the LNG carrier and the LNG bunkering shuttle was analyzed. The limiting wave height was determined from the maximum relative vertical motion between the floaters at the position of the LNG loading arms. The availability of the pile-guided LNG bunkering terminal was significantly improved owing to the reduced vertical motion. Finally, a cost–benefit analysis verified that the new mooring concept for an offshore LNG bunkering terminal was economically feasible.

This study proposes a molten carbonate fuel cell (MCFC)-based hybrid propulsion system for a liquefied hydrogen tanker. This system consists of a molten carbonate fuel cell and a bottoming cycle. Gas turbine and steam turbine systems are considered for recovering heat from fuel cell exhaust gases. The MCFC generates a considerable propulsion power, and the turbomachinery generates the remainder of the power. The hybrid systems are evaluated regarding system efficiency, economic feasibility, and exhaust emissions. The MCFC with a gas turbine has higher system efficiency than that with a steam turbine. The air compressor consumes substantial power and should be mechanically connected to the gas turbine. Although fuel cell-based systems are less economical than other propulsion systems, they may satisfy the environmental regulations. When the ship is at berth, the MCFC systems can be utilized as distributed generation that is connected to the onshore-power grid.

This study proposed a liquefied natural gas (LNG)-liquid hydrogen (LH2) hybrid propulsion system for a 267,000 m3 LNG carrier to be compliant with the energy efficiency design index (EEDI) requirement for CO2 emissions from ships in the near future and evaluated the system with regard to the aspects of the EEDI, hybrid fuel ratio, installation area, safety, and economics. The system design parameters were adjusted to satisfy the EEDI of Phases 4 and 5, which were less than the current EEDI requirement by 14% and 28%, respectively. The propulsion power of 6 MW should be generated in Phase 4 from hydrogen that accounted for 3% of the total mass of LH2 and LNG fuel. The CO2-free power generation in Phase 5 was increased to 13 MW, corresponding to 6% of the total fuel mass. The LH2 price was $2.0/kg and $2.4/kg for Phases 4 and 5, respectively, to gain an economic competitiveness against the conventional LNG-based propulsion system.

This paper presents a new approach to the structural availability quantification of a slender beam element affected by external random loads with a special focus on yield strength. The proposed method introduces the concept of structural availability, which is intrinsically identical to the concept of operational availability in system reliability engineering. Structural availability is formulated with structural failure and repair models. The failure model is determined based on failure probability and the Poisson approximation. In applying the structural availability method to design, it is possible to quantitatively measure features related to the operation and maintenance of structures and to identify cost-effective design options. To understand feasibility levels of structural availability, two cases based on actual design data are examined using the proposed method. The case study results illustrate not only processes of quantifying the structural availability of a beam element but also the cost-effectiveness evaluations on specific design options.

This study proposed a storage-generation system for a distributed-energy generation using liquid air combined with liquefied natural gas (LNG). The system comprised three main sites: the renewable-electricity sources (RESs), liquid-air energy storage (LAES), and natural-gas combustion. The low-priced off-peak electricity generated by the RESs was supplied to the LAES. The supplied electricity and previously stored cold energies liquefied the air. At the on-peak time, the liquid air and LNG were pressurized, re-gasified, and burnt immediately after mixing to generate the high-priced electricity while their cold energy was stored in thermal media. The proposed system was evaluated in terms of the thermodynamic, environmental, and economic performances. Its round-trip and storage efficiencies were 64.2% and 73.4%, respectively. The exergy efficiency of the storage-site, the generation-site, and the system was 70.2%, 75.1%, and 62.1%, respectively. The levelized cost of energy (LCOE) ranged from 142.5 to 190.0 $/MWh depending on the sizes and the storage time. The proposed system was compared to the diabatic compressed air-energy storage (CAES) systems and the adiabatic LAES system. The sensitivity analyses compared the systems for the fixed power output and storage time, and for the option to use natural gas. The proposed system showed better storage and round-trip efficiencies than those of comparison systems. Its LCOE was competitive with those of the compared systems except for the under-ground CAES system. The proposed system was an economic and viable option considering the geographical limitations and the environment impacts of the CAES system.

This study presents the effect of ortho-para conversion on the economics of transoceanic shipping of liquid hydrogen (LH2) based on an LH2 tanker. Four representative ortho concentrations of 30%, 2...

This study introduced economically-viable continuous reactive distillation (RD) design alternatives for cyclohexanol production through the indirect hydration of cyclohexene. The feasibility concept of batch RD was employed for generating the new design alternatives. The first alternative process utilized a continuous stripper for recovering the stable node product of cyclohexyl formate in the esterification reaction and then employed a continuous middle vessel column (MVC) for recovering the stable and unstable node products of cyclohexanol and formic acid in the hydrolysis reaction. The second design had a single MVC-type column having the reactive rectifying zone and the middle vessel reactor for the two respective reactions. The simulation results showed the two alternative sequences required less energy duty than the previously proposed RD process. However, compared to the prior RD process, the life cycle cost (LCC) of the first alternative design increased about 30% due to high equipment costs and the LCC of the second process decreased nearly 40% because of low equipment costs and energy requirements.

The present experimental study investigates the pressurization effect in a fluid storage tank injected with superheated vapor. The pressurizing system re-injects high-temperature forced boil-off gas (BOG), which is emitted after heating a portion of liquid with an external heater connected to the liquid storage tank, to pressurize the liquid. The experimental equipment comprises a vertical-type pressurizing tank having a volume of 8.2 liter and a mini-vaporizer that utilizes the heater. NOVEC 649 refrigerant was used. A mathematical formulation, which can effectively predict pressure rise by considering the material and energy transfer at the interface, was suggested. The experimental results indicated that the pressurizing time reduces as the initial liquid filling ratio and heat input rate increase. It was found that the actual time required to reach the target pressure can be reduced by up to approximately 1/3 the time calculated from the homogeneous model. Without considering the heat transfer via the interface, the model results of pressure rise is approximately 10% higher than the experimental value.

This study proposes a fuzzy-based FMEA (failure mode and effect analysis) for a hybrid molten carbonate fuel cell and gas turbine system for liquefied hydrogen tankers. An FMEA-based regulatory framework is adopted to analyze the non-conventional propulsion system and to understand the risk picture of the system. Since the participants of the FMEA rely on their subjective and qualitative experiences, the conventional FMEA used for identifying failures that affect system performance inevitably involves inherent uncertainties. A fuzzy-based FMEA is introduced to express such uncertainties appropriately and to provide flexible access to a risk picture for a new system using fuzzy modeling. The hybrid system has 35 components and has 70 potential failure modes, respectively. Significant failure modes occur in the fuel cell stack and rotary machine. The fuzzy risk priority number is used to validate the crisp risk priority number in the FMEA.

The rapid increase in demand for ecofriendly ships fueled by liquefied natural gas (LNG) has led to the proposal of floating large-capacity bunkering terminals at sea. Although computational fluid dynamics (CFD) simulations on preventing gas accidents on LNG-fueled ships and bunkering facilities have been carried out, research on evacuating humans in the event of disasters such as fire and explosion due to gas leakage has been insufficient. In this study, an algorithm was derived that considers the interaction between workers and gas accidents for evacuation to the open deck of a floating bunkering terminal, and a simulation platform was developed for visualizing gas accidents. The developed algorithm and simulation platform were applied to analyzing the evacuation characteristics considering both the gas accident and evacuation destination, and the results were compared with those of existing commercial software under the same conditions. The results demonstrated that considering the human characteristics of evacuees and their interaction with risk factors is important for simulating crowd evacuation more realistically.

This study estimated the life-cycle cost (LCC) of a ship-based carbon capture and storage (CCS) chain to determine the optimal volume of temporary storage tanks. The temporary storage tanks should be installed in the ship-based CCS chain to enable ship transportation. Concepts of the ship-based CCS chain were suggested with different volumes of the temporary storage tanks. They were analyzed from an economic viewpoint by LCC analysis. Although general LCC is composed of capital expenditure (CAPEX) and operation expenditure (OPEX), this study additionally considered the unavailability cost, which was derived from the availability. The availability indicates the operational effectiveness depending on the volume of the temporary storage tanks. For estimating the availability, factors causing production loss in the chain were defined first. The failure frequency and restoration time of the defined factors were collected and then the chain was modeled. Finally, the unavailability cost was estimated. CAPEX and OPEX were calculated using a commercial tool and relevant literature. The results showed that the unavailability cost decreased with the increment of the volumes of the temporary storage tanks. In contrast, the CAPEX and OPEX increased with the volumes. When the temporary storage tanks had the same volume of a CO2 carrier, the lowest LCC was indicated. A sensitivity analysis was performed to investigate the influence of different design parameters and assumptions: CO2 trade cost, the number of CO2 carriers, cargo volume of a CO2 carrier, and distance from a source to a sink.

This paper proposes design principles of a new concept prismatic pressure vessel that is primarily constructed of plane surfaces. These principles were compared with those of conventional pressure vessel which is primarily constructed of revolutionary surfaces. Considering structural characteristics of prismatic pressure vessel, membrane force and bending moment were calculated individually. Formulas including maximum bending moment and membrane force effects were illustrated by applying Levy's method and superposition method. For total stress at the plate of the pressure vessel, membrane force effects obtained from the shear loads of adjacent plates were included to enable to get more accurate solutions. The proposed simplified formulas for prismatic pressure vessel were suggested so that they can be applied for all dimensions and thicknesses. Case studies were conducted to verify the formulas by comparing with FEM results. By providing an overview of the stress relations of a non-stiffened type prismatic pressure vessel, the design principle of a prismatic pressure vessel shows distinctive concept to the conventional cylindrical pressure vessel. The membrane force effect studied in this research will be useful in the design of larger pressure vessels that require stiffeners.