• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.653-662
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• 2014

In this study, Mokpo national maritime university Training ship Centralizes Air Conditioning System was upgraded by installing onboard an Air-cooled Air conditioner. This resulted in the improvement of the performance and operation. This study compared refrigeration performance to former equipment and improving one. And through the actual measurement study about the cabin thermal environment, it will be used as basic data for marine air conditioning design and plan in the future. At same climate condition, when the Centralized Air Conditioning System and an improved air conditioning system operated, cabin temperature was at $24{\sim}28^{\circ}C$, humidity was 55~75 % as comfortable condition, Generator load measurement showed a saving of 48KW in the average load and 8 % in the full load factor. This also resulted in a saving of daily fuel oil consumption(FOC) at around 222 [${\ell}/day$] average. On the other hand, one cadet cabin(Cadet No.21) indicated a higher temperature due to heat transmission of engine room. It found us not to consider installing additional diffuser to reduce the heat transmission.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1044-1053
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• 2022

Time domain reflectometry (TDR) is a diagnostic technique to evaluate the physical integrity of cable and finds application in leak detection and localization of piping system. In this study, a cable-shaped leak detection sensor was proposed using the TDR technique for monitoring leakage detection of ship's engine room seawater piping system. The cable sensor was developed using a twisted pair arrangement and wound by an absorbent material. The availability and performance of the sensor for leak detection and localization were evaluated on a lab-scale pipeline set up. The developed sensor was installed onto the pipes and flanges of the lab-scale set up and various TDR waveforms were acquired and analyzed according to the dif erent variables including the number of twists and sheath thickness. The result indicated that the twisted cable sensor was able to produce clear and smooth signal as compared to the TDR sensor with a parallel arrangement. The optimal number of twist was determined to be above 10 per the unit length. The optimal diameter of sheath thickness that results in the desired sensitivity was determined to be ranging from 80% up to 120% of the diameter of the conductor. The linear regression analysis for estimation of leak localization was carried out to estimate the location of the leakage, and the result was a determination coefficient of 0.9998, indicating a positive relationship with the actual leakage point. The proposed TDR based leak detection method appears to be an effective method for monitoring leakage of ship's seawater piping system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1131-1136
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• 2015

In a diesel engine, the wear of the cylinder liner occurs because of the continuous reciprocating motion of the piston ring. This wear reduces the performance of the diesel engine and shortens its service life. This study evaluated the wear characteristics of GT metal and a conventional metal used for cylinder liners using a ship's diesel engine. Wear tests were performed at temperatures of $25^{\circ}C$, $175^{\circ}C$, and $325^{\circ}C$, and under loads of 10 N, 30 N, and 50 N. The amount of wear, specific wear rate, and friction coefficient were evaluated for each condition. To analyze the wear mechanism, observations were made on an SEM. In the case of both metals, abrasive and adhesion wear occurred on the wear surfaces at room temperature, and corrosion wear was observed at high temperatures. The amount of wear and the specific wear rate of the GT metal were lower than those of the conventional metal at all temperatures, and hence it can be concluded that the wear characteristics of the GT metal are much better.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.366-371
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• 2021

This study suggests surface wave communication, which uses a metal surface as a medium, to provide wireless communication in the extreme environment due to surrounding metal materials on vessels. The test was conducted on a G/T 265 tons tug boat to confirm the possibility of surface wave communication between a bridge and each designated space in the ship. As a result, the transmission speed was 13Mbps on average. In a test case of the bridge via the engine room, the transmission speed was 4.3Mbps on engine running and 1.2Mbps on sailing. It overcame this by partially changing the equipment installation location. Surface wave communication in bow storage, a fully enclosed space, had 8Mbps better transmission speed than wireless communication; this confirmed the superiority of surface wave communication in confined spaces on a vessel. Additional surface wave generators were designed and applied to resolve the paint issue. It is expected to use surface wave communication to implement the new wireless solution for Maritime-IoT system on vessels.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1150-1155
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• 2014

To prevent the flame spread in FRP vessel in fire, the engine-room of the vessel should be constructed additionally with laminated fire-retardant resin over 3 times or equivalent insulation materials to former according to the relevant standard for FRP vessel structure. It is surveyed that insulation materials called 'Gel coat' are widely used in FRP fishing vessel, however, test method and its criteria for Gel coat are not clearly establish and have not been evaluated yet, while test method and criteria for fire-retardant resin and fire-retardant polyurethane composite are described in test standard for type-approval. In this study, 3 fire-retardant resins, 4 gel coats, 1 flame-retardant paint and 1 polyurethane composite were selected based on the survey and were evaluated according to both IMO FTP Code part 5 and flame-retardant test. When comparing based on CFE values from flame-spread test, average value for 4 gel coats were lower than that of 3 fire-retardant resins. As for flame-retardant test, there were no significant differences between fire-retardant resin and gel coat, based on charred area.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.89-99
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• 1990

It is required to develop a hull form with low resistance and high propulsive efficiency for the improvement of the ship-board operational economy. Since the hull forms with low resistance frequently have lower propulsive efficiency and on the other hand the hull forms with higher propulsive efficiency don't show good resistance characteristics, it is always very difficult to obtain economical hull forms which require less propulsive power accordingly. Efforts have been made to pursue a stern form with excellent resistance and propulsion characteristics together by shaping the run of the so-called buttock-flow type stern, which is known to have good viscous resistance performance, like that of conventional aftbody(U-type or Hogner type) featured by high propulsive efficiency. First model tests confirmed that the above concept can be one of the alternative approaches to the design of the good stern form and by the continuing efforts thereafter for the refining of the concept, propelled by the first promising results, stern form of good resistance performance together with good propulsive efficiency has been realized to some extent. In addition, it is confirmed that the new new stern can have better cavitation and vibration characteristics due to uniform wake-fields and the compact engine room arrangement can be possible due to it's larger floor area in way of engine room double bottom as compared with usual barge stern.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1209-1215
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• 2022

The selective catalytic reduction (SCR) is known as a very efficient method to reduce nitrogen oxides (NOx) and the catalyst performs reduction from nitrogen oxides (NOx) to nitrogen (N₂) and water vapor (H2O). The catalyst, which is one of the factors determining the performance of the nitrogen oxide (NOx) ruduction method, is known to increase catalyst efficiency as cell density increases. In this study, the reduction characteristics of nitrogen oxides (NOx) under various engine loads investigated. A 100CPSI(60Cell) catalysts was studied through a laboratory-sized simulating device that can simulate the exhaust gas conditions from the power generation engine installed in the training ship SEGERO. The effect of 100CPSI(60Cell) cell density was compared with that of 25.8CPSI(30Cell) cell density that already had NOx reduction data from the SCR manufacturing. The experimental catalysts were honeycomb type and its compositions and materials of V₂O₅-WO₃-TiO₂ were retained, with only change on cell density. As a result, the NOx concentration reduction rate from 100CPSI(60Cell) catalyst was 88.5%, and IMO specific NOx emission was 0.99g/kwh satisfying the IMO Tier III NOx emission requirement. The NOx concentration reduction rate from 25.8CPSI(30Cell) was 78%, and IMO specific NOx emission was 2.00g/kwh. Comparing the NOx concentration reduction rate and emission of 100CPSI(60Cell) and 25.8CPSI(30Cell) catalysts, notably, the NOx concentration reduction rate of 100CPSI(60Cell) catalyst was 10.5% higher and its IMO specific NOx emission was about twice less than that of the 25.8CPSI(30Cell) catalysts. Therefore, an efficient NOx reduction effect can be expected by increasing the cell density of catalysts. In other words, effects to production cost reduction, efficient arrangement of engine room and cargo space can be estimated from the reduced catalyst volume.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1240-1247
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• 2008

Leakage trouble on the sea water pipeline in engine room is often resulted from a localized corrosion due to severe corrosive environment caused by both high speed and high pressure of sea water flowing through the inner pipe. In addition, when the ship is in stand-by or emergency condition, underwater welding to control the leakage of sea water from a hole of its pipe is very important in an industrial safety point of view. In this study possibility of underwater welding to control leakage of sea water and corrosion property of its welding zone were investigated with the electrochemical methods by parameters of welding methods and welding electrodes when underwater welding is achieved with a such case that sea water is being leaked out with a height at 50mm from a hole of $2.5mm{\emptyset}$ of test pipe. Corrosion resistance of weld metal zone is better than the base metal and its hardness is higher than that of the base metal. However corrosion potential of weld metal zone showed a negative value than that of the base metal, therefore weld metal zone is preferentially corroded rather than the base metal by performance of galvanic cell due to difference of corrosion potential between weld metal zone and base metal. Eventually it is suggested that leakage of sea water is successfully controlled by underwater welding,

• Fire Science and Engineering
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• v.19 no.2 s.58
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• pp.37-44
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• 2005

We have conducted a numerical simulation under three-dimensional unsteady conditions in order to analyze the characteristics of flow and the distribution of $CO_2$ agent concentration according to the number of $CO_2$ agent nozzle. The engine room of a ship was selected as a protection space, and flow fields and $CO_2$ concentration fields were measured. In case of increasing the number of $CO_2$ nozzle from 2 nozzles to 4 nozzles, the distribution of CO2 concentration showed low, and in case of increasing the number of $CO_2$ nozzle to above 6 nozzles, the recirculating flow affected to all region was generated. In case of increasing the number of $CO_2$ agent nozzle to above 4 nozzles, the iso-concentration line below 0.36 expanded or contracted slightly. Therefor, the proper number and the arrangement of $CO_2$ agent nozzle are considered when $CO_2$ fire fighting system is designed.

• Journal of Ocean Engineering and Technology
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• v.21 no.5
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• pp.39-46
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• 2007

The sea water pipe of a ship's engine room is a severely corrosive environment caused by fast flawing sea water containing chloride ions and high conductivity. Therefore, leaking of sea water may occur as a result of local corrosion of the welded zone. Leaking is usually controlled by various welding methods. In this study, when the sea water pipe is welded with certain welding methods and welding electrodes, the corrosion resistance of WM (Welding metal) and HAZ (Heat affected zone) was investigated using electrochemical methods. Although the corrosion potential of the HAZ is higher than that of WM, the corrosion resistance of WM is superior to HAZ. However, when WM and HAZ are both opened to the sea water, the WM part with the anode was more seriously corroded than was the HAZ of the cathode by performance of a galvanic cell due to difference of the corrosion potential between HAZ and WM. In particular TIG welding showed relatively good results in corrosion resistance of both HAZ and WM compared to other welding methods.