• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.51-57
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• 2021

The seawater cooling system of naval ships is installed to remove the toxic substances generated by CBR (Chemical, Biological, and Radiological) warfare and reduce the infrared signature of naval ships from outside the hull. The dispersion range of the nozzle is determined according to the injection pressure of seawater and the nozzle type. Therefore, it is necessary to select the appropriate injection pressure and design the optimal nozzles to increase the seawater dispersion area and maximize the efficiency of the cooling system. In this study, the applying feasibility of 3D printing technology to produce an injection nozzle for the seawater cooling system was examined. To this end, the extruded plastic specimens were fabricated by 3D printing, and the physical properties of the specimens were estimated through tensile testing. After this, the strain and stress of the nozzle as a function of the pressure were simulated by applying the estimated results to the finite element analysis. The finite element analysis results showed that the nozzle remained within the elastic range at the optimal pressure. The nozzle was estimated to be structurally stable, and the possibility of this study was confirmed.

• Journal of Korean Society of Disaster and Security
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• v.14 no.1
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• pp.1-8
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• 2021

A corrugated pipe is widely used in firefighting equipment and sprinkler pipes because of its elasticity, which is less damaged by deformation and convenient facilities. However, the corrugated shape of the wall results in complex internal turbulent flow, and it is difficult to predict the pressure drop, which is an important design factor for pipe flow. The pressure drop in the corrugated tube is a function of the shape factors of the pipe wall, such as groove height, length, and pitch. Existing studies have only shown a study of pressure drop due to length changes in the case of D-shaped tubes with less than 5 pitch (P) and height (K) of the rectangular grooves in the tube. In this work, we conduct a numerical study of pressure drop for P/Ks with length and height changes of 2.8, 3.5 and 4.67 with Re Numbers of 55,000, 70,000 and 85,000. The pressure drop in the corrugated tube was interpreted to decrease with smaller P/K. We show that the pressure drop is affected by the change in the groove aspect ratio, and the increase in the height of the groove increases the recirculation area, and the larger the Reynolds number, the greater the pressure drop.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1100-1109
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• 2022

Herein, a case study was conducted on the bilge pumping performance of a 24,000TEU class container ship with an overall length of 400m. Although the bilge system of the 24,000TEU class container ship was designed in accordance with the rule requirements of the Classification Society, the bilge system did not satisfy the 2 m/s requirements of SOLAS Reg.II-1/35-1 under the rated flow rate and maximum flow rate conditions of the bilge pump installed in the ship. In particular, assumptions were made that No.1 ~ No.4 cargo holds were flooded and filled entirely by sea water and the evaluation of bilge pumping performance had been performed for No.1 ~ No.4 cargo holds. According to the evaulation results of the, the mean water velocity at the main bilge pipe for No.2, No.3, and No.4 cargo holds did not meet the 2 m/s criterion. To resolve this problem, in this study, the branch bilge pipe in each cargo hold was changed from 150A to 200A and the mean water velocity at the main bilge pipe for No.2, No.3, and No.4 was calculated as 2.479m/s, 2.476m/s, and 2.459m/s, respectively.

• Journal of the Society of Disaster Information
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• v.19 no.3
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• pp.608-623
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• 2023

Purpose: Recently, the number of logistics warehouses has been on the rise. In addition, as the number of such logistics warehouses increases, number of fire accidents also increases every year, increasing the importance of preventing fires in large logistics warehouses. Method: investigated aspirating smoke detectors that are emerging as adaptive fire detectors in logistics warehouses. Then, through fire simulation (FDS), logistics warehouse modeling was conducted to compare and analyze the detection speed of general smoke detectors and aspirating smoke detectors according to four stages of fire growth and three locations of fire in the logistics warehouse. Result: Growth speed in Slow-class fires and Mediumclass fires, the detection speed of aspirating smoke detectors was faster regardless of the location of the fire. However, in Fast-class fires and Ultra-Fast-class fires, it was confirmed that the detection speed of general smoke detectors was faster depending on the location of the fire. Conclusion: It was confirmed that the detection performance of the aspirating smoke detector decreased as the fire growth speed increased and the location of the fire occurred further than the receiver of the aspirating smoke detector. Therefore, even if an aspirating smoke detector is installed in a warehouse that stores combustibles with high fire growth rates, it is judged that an additional smoke detector is attached far away from the receiver of the general smoke detector to increase fire safety.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.29 no.2
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• pp.118-129
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• 2011

This study is about the governor general's official residence and its garden in Yongsan that were constructed during the Japanese occupational time. The garden design drawing was also made while planning such Neo-Baroque style building, and it contains particular information of the garden unlike the other existing landscape drawings. The content of garden translated and landscape historical value drawn out by analysis of garden drawings, press articles and literatures are as follows; First, such governor general's official residence garden in Yongsan is likely to be the Korean first western style landscape form. For, from the point that it was completely constructed together with such official residential building in 1909, its construction time should be before that of the garden of Seokjojeon, Deoksu Palace, which was constructed in 1911. Second, it shows the garden style and garden planting factors introduced together with the modern architecture then. Such garden planting factors are placed from the center axis of the garden that is connected to the center of the building and monument as well. Such style and factors cover and show the flower bed appearing in Baroque style gardens, the monument that forms Vista playing the center of audience's vision, water space that is placed symmetrically against the axis, planting pattern that emphasizes the plants' space, flower bed shape and axis, and what kinds of plants were introduced then. Third, it shows the using pattern of western style gardens. Western style garden parties used to take in place in this garden while official dinner and reception were held in the evening in the official residence. Fourth, it shows the historical value as a modern landscape drawing, which is the Korean first landscape drawing that shows the plants' names and planting techniques marking the current height and planned height for change of topography and water system as a water landscape factor. That is, this drawing has the value that it was upgraded from the other existing ones that expressed only simple plants' symbols or flower bed shapes. I, therefore, hope that the studies on the modern landscape would be getting wider by excavation of new historical records in the future.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.12
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• pp.1098-1125
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• 2000

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 1998 and 1999 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. 1) A review of the recent studies on fluid flow, turbomachinery and pipe-network shows that many experimental investigations are conducted in applications of impingement jets. Researches on turbulent flows, pipe flows, pipe-networks are focused on analyses of practical systems and prediction of system performance. The results of noise reduction in the turbomachinery are also reported. 2) A review of the recent studies on heat transfer analysis and heat exchanger shows that there were many papers on the channel flow with the application to the design of heat exchanger in the heat transfer analysis. Various experimental and numerical papers on heat exchanger were also published, however, there were few papers available for the analysis of whole system including heat exchanger. 3) A review of the recent studies on heat pump system have focused on the multi-type system and the heat pump cycle to utilize treated sewage as the heat source. The defrosting and the frosting behaviors in the fin-tube heat exchanger is experimentally examined by several authors. Several papers on the ice storage cooling system are presented to show the dynamic simulation program and optimal operation conditions. The study on the micro heat pipes for the cooling of high power electronic components is carried out to examine the characteristics of heat and mass transfer processed. In addition to these, new type of separate thermosyphon is studied experimentally. 4) The recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. New systems operating with natural refrigerants are drawing lots of attention. In addition to these, evaporation and condensation heat transfer characteristics of traditional and new refrigerants are investigated for plain tubes and also for microfin tubes. Capillary tubes and orifice are main topics of research as expansion devices and studies on thermophysical properties of new refrigerants and refrigerant/oil mixtures are widely carried out. 5) A review of the recent studies on absorption cooling system shows that numerous experimental and analytical studies on the improvement of absorber performance have been presented. Dynamic analysis of compressor have been performed to understand its vibration characteristics. However research works on tow-phase flow and heat transfer, which could be encountered in the refrigeration system and various phase-change heat exchanger, were seemed to be insufficient. 6) A review of recent studies on duct system shows that the methods for circuit analysis, and flow balancing have been presented. Researches on ventilation are focused on the measurement of ventilation efficiency, and variation of ventilation efficiency with ventilation methods by numerous experimental and numerical studies. Furthermore, many studies have been conducted in real building in order to estimate indoor thermal environments. Many research works to get some information for cooling tower design have been performed but are insufficient. 7) A review on the recent studies on architectural thermal environment and building mechanical systems design shows that thermal comfort analysis is sitting environment, thermal performance analysis of Korean traditional building structures., and evaluation of building environmental load have been performed. However research works to improve the performance of mechanical system design and construction technology were seemed to be insufficient.