Carbon neutrality by 2050 was declared and are focusing on developing innovative energy technologies aimed at reducing greenhouse gas emissions. Active investment and research are underway in the full-cycle development of hydrogen energy technologies, including hydrogen production, storage, transportation, and utilization, which is gaining attention as a promising future eco-friendly energy source. The storage density of liquid hydrogen is 70.79kg/m3, which is higher than the 41kg/m3 of compressed hydrogen at 700bar, making it more suitable for large-scale storage. To store hydrogen at 20K, insulation technologies such as vacuum insulation, powder insulation, or multi-layer insulation (MLI) are typically required. Consequently, there is active research being conducted on the design of insulation systems and materials. However, research on the design for improving the structural integrity of the supports between the inner and outer tanks remains insufficient. n this study, topology optimization was performed for the support design of a liquid hydrogen storage tank using commercial finite element analysis (FEA) software. The structural safety was validated through structural analysis of a simplified self-designed model.

This study aims to optimize the orifice diameter to reduce pressure hunting in the pilot valves of positioners used in nuclear power plant control systems. Computational Fluid Dynamics (CFD) analysis using ANSYS CFX was conducted to create 3D models with varying orifice diameters (1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm). To enhance the accuracy of the analysis, boundary layer meshing techniques (Inflation) were applied, and the SST k-ω turbulence model was employed. The analysis of pressure variation and pressure hunting over time revealed that larger orifice diameters resulted in reduced pressure hunting, with a 3 mm orifice diameter achieving 0% pressure hunting. Additionally, it was observed that larger orifice radii slightly increased the average outlet pressure. Based on the findings, a 3 mm orifice diameter is recommended to effectively mitigate pressure hunting in pilot valves, contributing to improved system stability in nuclear power plants. Future studies will explore the design of slanted orifices to further analyze fluid flow characteristics.

The reliability of control valves is critical in nuclear power plants to ensure precise fluid regulation and prevent risks associated with overheating or decreased efficiency. Recently, the supply of imported control valves used in these plants has been discontinued, making the development of domestic alternatives an urgent necessity. This study focuses on the design of an orifice in the pilot valve pipe of a positioner to reduce hunting, a key issue that compromises control stability. Fluid analysis was conducted using ANSYS CFX to investigate the fluid behavior in the pipe with the orifice. The analysis methods included enhanced meshing techniques, turbulence models, and residual values to improve convergence and accuracy. To meet the operational requirements of nuclear power plants (outlet pressure: 3.2 bar, inlet pressure: 7 bar), the inlet fluid velocity was determined. The pressure and pressure hunting were analyzed. Results showed that the selected inlet velocity satisfied the operational conditions, and pressure hunting values were measured and analyzed. The findings provide a basis for further optimizing orifice shapes to achieve the target pressure hunting value of 0.5%.

Globally, there is a concentrated effort to lead in alternative energy technologies. Among various eco-friendly energy sources and carbon-free fuels, hydrogen energy is gaining attention as a clean energy solution for future industries, as its only byproduct is water. There are two primary storage methods: compressing hydrogen gas at high pressure and storing it as a liquid. Research on insulation, including the structural design of multi-layer Insulation (MLI) and vapor-cooled shield (VCS), as well as the materials used for insulation, has been actively conducted. However, studies focused on improving the structural safety of the supports that sustain the structure between the inner and outer tanks have been limited. In this study, a thermal-structural coupled analysis technique for liquid hydrogen storage tanks was developed using commercial finite element analysis software for the design of support structures for liquid hydrogen storage tanks. Six analytical models were created based on varying the number and diameter of the supports with the constant total volume of the supports and a structurally safe support configuration was proposed.

The recent surge in energy consumption has sharply increased the use of fossil fuels, leading to a steep rise in the concentration of greenhouse gases in the atmosphere. Interest in hydrogen is growing to mitigate the issue of global warming. Currently, hydrogen energy is transported in the form of high-pressure gaseous hydrogen, which has the disadvantages of low safety and energy efficiency. To develop commercial hydrogen vehicles, liquid hydrogen should be utilized. Liquid hydrogen storage tanks have supports between the inner and outer cylinders to bear the weight of the cylinders and the liquid hydrogen. However, research on the design to improve the structural safety of these supports is still insufficient. In this study, through a thermal-structural coupled analysis of liquid hydrogen storage tanks, the model with three supports, which had the lowest maximum effective stress in the outer tank, inner tank, and supports as proposed in the author's previous research, was used to create analysis models based on the diameter of the supports. A structurally safe design for the supports was proposed.

The government declared ‘2050 carbon neutrality’ as a national vision in October 2020 and subsequently pursued the establishment of a ‘2050 carbon neutrality scenario’ as a follow-up response. Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support structures for liquid hydrogen storage tanks, a thermal-structural coupled analysis technique was developed using Ansys Workbench. Analytical models were created based on the number and arrangement of supports to propose structurally safe support designs.

Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. However, the low density of hydrogen makes its storage an urgent technical problem for hydrogen energy development. Compared with the density of gas hydrogen, the density of liquid hydrogen is more than 1.5 times higher. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support for liquid hydrogen storage tank, technique of thermal-structural coupled analysis including geometry, mesh, and boundary condition were developed using Ansys workbench, and equivalent stress and deformation distributions were analyzed.

Decarbonization plays an important role in future energy systems for establishing a zero-carbon society. Hydrogen is believed to be a promising energy source that can be converted, stored, and utilized efficiently, leading to a broad range of possibilities for future applications. Hydrogen can be stored in various forms, including compressed gas, liquid hydrogen, hydrides, adsorbed hydrogen. Among these, liquid hydrogen has high gravimetric and volumetric hydrogen densities. There are a lot of previous studies on thermal behavior of MLI and VCS and optimization insulation system, but research on the insulation performance by varying the head shape of the tank has not been conducted. In this study, thermal-structural coupled analysis was conducted on the insulation system with VCS positioned between two layers of MLI for a liquid hydrogen storage tank. The analysis considered dome shapes (torispherical, circle, ellipses), and heat flux and temperature were derived from thermal analysis to predict insulation performance. Maximum equivalent stress and deformation were calculated from the structural analysis, and the optimal dome shape was proposed.

Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable and high calorific value. The long-term storage of liquid hydrogen with low heat leakage is essential for future deep space exploration. Because of low critical temperature and volatility, liquid hydrogen tank poses severe requirements to multi-layer insulation (MLI). In order to reduce heat leak into tank, vapor cooled shield (VCS) was set up to cool MLI by retrieving the heat of discharged cryogenic gas hydrogen. This paper presents an parametric study on insulation system in liquid hydrogen storage vessel with MLI and VCS. Thermal model was developed, and heat transfer analysis by varying VCS position was conducted. Temperature and heat flux distributions along time passing were derived, and effect of VCS position on insulation performance was investigated.

The flange spreader has been used to withdraw butterfly valves during maintenance. The typical flange spreaders required an excessive working space, and the pipe and flange are damaged by the load. In the previous study, the author developed a valve easy out tool with collet, and designed collet shape to ensure structural safety. However, clamping force of the collet had not been checked. In this study, design of collet shape was performed to improve clamping force. Techniques of structural analysis were established and design parameters were selected. Through parametric study, the collet shape with clamping force of 159,748N was suggested. This will contribute to stability and efficiently of valve maintenance.

The flange spreader has been used to withdraw gaskets and valves during butterfly valve maintenance. When using the conventional flange spreader, an excessive working space (pipe separation distance) appears, and the pipe and flange are damaged by the load. Also, the equipment can’t be operated safely when the pipe has eccentric fitting. To solve the problems, a valve easy out tool with collet was developed for safely fixing and spreading flange. By using Ansys Workbench 2021 R2, the structural analysis of the original collet was performed, and shape design of the collet was carried out to improve structural safety.