• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.647-655
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• 2021

The IMO (International Maritime Organization) is discussing the improvement of energy ef iciency of ships in order to reduce greenhouse gas emissions from ships. Currently, by applying an ORC power generation system using waste heat generated from ships, high energy conversion efficiency can be expected from ships. This technology uses an organic medium based on Freon or hydrocarbons as the working fluid, which evaporates at a lower temperature range than water. Through this, it is possible to generate steam (gas) and generate power at a low and low temperature relatively. In this study, the analysis of heat flow between the refrigerant and waste heat in the ORC power generation system, which is an organic Rankine cycle, is analyzed using 3D simulation techniques to determine the temperature change, velocity change, pressure change, and mass change of the fluid flowing of the WHRU (Waste Heat Recovery Unit) inside and the outside the structure. The purpose of this study is to analyze how the mass change affects the structure, and this study analyzed the heat transfer of the heat exchanger from the refrigerant and the exhaust gas of the ship's main engine in the ORC power generation system using this technique.

• Trans-
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• v.12
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• pp.81-106
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• 2022

The possibility of metaverse system to be a catalyst for hyper-connected society will be dependent on the speed of connected technological development and its social utilization in the same manner as AI technology. Putting these technical realization processes in brackets, this paper focus on some philosophical-political issues in connection with cognitive-ecological changes in the future cinema which will be influenced by the complexive techno-socio couples of accelerated development of metaverse system. Generally speaking, essence of metaverse system seems to be the degree of immersion by technical accuracy, but is not true. In perspective of cognitive-ecology, flow degree of a picture or photograph is relied not on 'accuracy of representation' but on its message's contextual link-up. In this aspect, real potentiality of metaverse system shall be understood in the context of cognitive-ecological changes of human brain's multi-intelligence networking abilities(intersection of augmentation-simulation and outside-inside) which will be activated in the new structure of natural-social-technological coupling of metaverse system. These cognitive-ecological potentialities have been partially actualized in the cinematic process of tripod mimesis for the longest time, [real contradiction/conflicts (Mimesis-1) -->fictional solutions of cinema (Mimesis-2) --> selective interpretation of spectator's wish fulfillment (Mimesis-3) --> real change (Mimesis-1')]. Therefore metaverse's real potentiality must be considered to be dependent on the possibility of deepening and extending of cinematic circulation between real seperation/problems and ideal connection/solutions. In this context, advanced metaverse system can be compared as a modern technical version of ideal circulation of physics and metaphysics

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.163-172
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• 2024

In this study, two different scenarios for ammonia liquefaction in the green ammonia manufacturing process were proposed, and the economic-feasibility and environmental impact of each scenario were analyzed. The two liquefaction processes involved gas-liquid separation before cooling at high pressure (high pressure cooling process) or after decompression without the gas-liquid separation (low pressure cooling process). The high-pressure cooling process requires higher capital costs due to the required installation of separation units and heat exchangers, but it offers relatively lower total utility costs of 91.03 $/hr and a reduced duty of 2.81 Gcal/hr. In contrast, although the low-pressure cooling process is simpler and cost-effective, it may encounter operational instability due to rapid pressure drops in the system. Environmental impact assessment revealed that the high-pressure cooling process is more environmentally friendly than the low-pressure cooling process, with an emission factor of 0.83 tCO₂eq less than the low-pressure cooling process, calculated based on power usage. Consequently, the outcomes of this study provide relevant scenario and a database for green ammonia synthesis process adaptable to various process conditions.

• Journal of the Society of Disaster Information
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• v.11 no.1
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• pp.135-147
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• 2015

Recent underground common utility tunnels are underground facilities for jointly accommodating more than 2 kinds of air-conditioning and heating facilities, vacuum dust collector, information processing cables as well as electricity, telecommunications, waterworks, city gas, sewerage system required when citizens live their daily lives and facilities responsible for the central function of the country but it is difficult to cope with fire accidents quickly and hard to enter into common utility tunnels to extinguish a fire due to toxic gases and smoke generated when various cables are burnt. Thus, in the event of a fire, not only the nerve center of the country is paralyzed such as significant property damage and loss of communication etc. but citizen inconveniences are caused. Therefore, noticing that most fires break out by a short circuit due to electrical works and degradation contact due to combustible cables as the main causes of fires in domestic and foreign common utility tunnels fire cases that have occurred so far, the purpose of this paper is to scientifically analyze the behavior of a fire by producing the model of actual common utility tunnels and reproducing the fire. A fire experiment was conducted in a state that line type fixed temperature detector, fire door, connection deluge set and ventilation equipment are installed in underground common utility tunnels and transmission power distribution cables are coated with fire proof paints in a certain section and heating pipes are fire proof covered. As a result, in the case of Type II, the maximum temperature was measured as $932^{\circ}C$ and line type fixed temperature detector displayed the fire location exactly in the receiver at a constant temperature. And transmission power distribution cables painted with fire proof paints in a certain section, the case of Type III, were found not to be fire resistant and fire proof covered heating pipes to be fire resistant for about 30 minutes. Also, fire simulation was carried out by entering fire load during a real fire test and as a result, the maximum temperature is $943^{\circ}C$, almost identical with $932^{\circ}C$ during a real fire test. Therefore, it is considered that fire behaviour can be predicted by conducting fire simulation only with common utility tunnels fire load and result values of heat release rate, height of the smoke layer, concentration of O2, CO, CO2 etc. obtained by simulation are determined to be applied as the values during a real fire experiment. In the future, it is expected that more reliable information on domestic underground common utility tunnels fire accidents can be provided and it will contribute to construction and maintenance repair effectively and systematically by analyzing and accumulating experimental data on domestic underground common utility tunnels fire accidents built in this study and fire cases continuously every year and complementing laws and regulations and administration manuals etc.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.642-650
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• 2020

In general, the circulation path of the fluidized particles in a CFB (Circulating Fluidized Bed) boiler is such that the particles entrained from a combustor are collected by a cyclone and recirculated to the combustor via a sealpot which is one of non-mechanical valves. However, when a fluidized bed heat exchanger (FBHE) is installed to additionally absorb heat from the fluidized particles, some particles in the sealpot pass through the FBHE and then flow into the combustor. At this time, in the FBHE operated in the bubbling fluidization regime, if the heat flow is not evenly distributed by poor mixing of the hot particles (800~950 ℃) flowing in from the sealpot, the heat exchanger tubes would be locally heated and then damaged, and the agglomeration of particles could also occur by formation of hot spot. This may affect the stable operation of the circulating fluidized bed. In this study, the unevenness of heat flow arising from structural problems of the FBHE of the domestic D-CFB boiler was found through the operating data analysis and the CPFD (Computational Particle Fluid Dynamics) simulation using Barracuda VR. Actually, the temperature of the heat exchanger tubes in the FBHE showed the closest correlation with the change in particle temperature of the sealpot. It was also found that the non-uniformity of the heat flow was caused by channeling of hot particles flowing in from the sealpot. However, it was difficult to eliminate the non-uniformity even though the fluidizing velocity of the FBHE was increased enough to fluidize hot particles vigorously. When the premixing zone for hot particles flowing in from the sealpot is installed and when the structure is changed through the symmetrization of the FBHE discharge line for particles reflowing into the combustor, the particle mixing and the uniformity of heat flow were found to be increased considerably. Therefore, it could be suggested that the structural modification of the FBHE, related to premixing and symmetric flow of hot particles, is an alternative to reduce the non-uniformity of the heat flow and to minimize the poor particle mixing.