• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.280-286
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• 2009

In this study, the corrosion property of copper alloy tubes in seawater has been investigated. Three copper alloys of nominal composition Cu-20Zn-2Al(Al-Brass), Cu-30Ni(CN70/30) and Cu-10Ni(CN90/10) were considered. The samples were immersed in 3%NaCl flowing solution at $90^{\circ}C$ for 30, 50 and 80 days. Corrosion rate of copper alloy tubes in 3%NaCl flowing solution was investigated by weight-loss measurements and electrochemical test. The CN70/30 showed lowest corrosion rate among three copper alloy tubes. Because of passive films formation, corrosion rates of three types of copper tubes were decrease with time. Surface characteristics of copper alloy tubes were analyzed by optical micrograph(OM), scanning electronic microscopy (SEM), energy dispersive X-ray analysis(EDAX) and X-ray diffraction patterns(XRD). CN70/30 showed partly pitting problem on the surface owing to high Fe content, even though having high resistant against corrosion. Cracks appeared on the surface of CN90/10 and CN70/30 after more than 50 days immersion, which could be derived from high nickel contents.

• Journal of the Korean Solar Energy Society
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• v.34 no.5
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• pp.23-31
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• 2014

This study was accomplished to get the foundation design data of VMD(Vacuum Membrane Distillation) system for Solar Thermal VMD plant. VMD experiment was designed to evaluate thermal performance of VMD using PVDF(polyvinylidene fluoride) hollow fiber hydrophobic membranes. The total membrane surface area in a VMD module is $5.3m^2$. Experimental equipments to evaluate VMD system consists of various parts such as VMD module, heat exchanger, heater, storage tank, pump, flow meter, micro filter. The experimental conditions to evaluate VMD module were salt concentration, temperature, flow rate of feed sea water. Salt concentration of feed water were used by aqueous NaCl solutions of 25g/l, 35g/l and 45g/l concentration. As a result, increase in permeate flux of VMD module is due to the increasing feed water temperature and feed water flow rate. Also, decrease in permeate flux of VMD module is due to increasing salinity of feed water. VMD module required about 590 kWh/day of heating energy to produce $1m^3/day$ of fresh water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6098-6105
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• 2013

In the present study, the characteristics of corrosion and thermal conductivity of thermal spray coatings for seawater heat exchangers were examined experimentally. The coating types of theZn and Al thermal spray coatings with additional epoxy and silicone sealers were tested. To examine the corrosion characteristics of the thermal spray coating, the cyclic voltamogram curve was measured followed by SEM imaging for surface characterization. The laser flash method was usedto measure the thermal conductivity of the specimen. The conductivity test results showed that thermal conductivity decreased by3 ~ 4% with the silicone sealer and decreased by 70 ~ 75% with the epoxy sealer.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.282-287
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• 2016

Recently in order to protect the ocean environment and to reduce energy consumption, shipbuilders have been developing highly economized ships. This research analyzed the possibility of adopting the onshore absorption refrigerator to offshore ships having a cooling system with refrigerant by using the waiste heat of the engine jacket cooling water instead of compression refrigerators. The results showed that R236fa could be a suitable medium for absorbing the heat of the absorber and condenser in an absorption refrigerator. The cooling system using R236fa achieved a high COP of 0.798, which is 15% and 5% higher than an air cooling system with a cooling tower and a water cooling system with a heat exchanger, respectively. The cooling system with R236fa achieved high efficiency with a 25% reduction in flow rate of LiBr solution and only 15.7% flow rate of cooling medium as compared to the water cooling system. The heating of sea water by the engine jacket water flowing out from the generator can prevent the crystallization of LiBr solution due to the low temperature of sea water.

• Journal of Power System Engineering
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• v.7 no.4
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• pp.25-30
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• 2003

Hydrocyclone has been widely used for the solid-Liquid separation in many industrial sites because of its comparatively preferable applications that can be applied to wide-range panicle sizes. If seawater with impurities flows through pumps or heat exchanger, it might cause an decrease in efficiency of cooling system. In this paper, we have suggested solid methods of separating impurities from seawater in the cooling system by using a Hydrocyclone. The effects of design factors as solid concentration, cyclone inlet pressure, flow rate and diameter of underflow on the seperating performance of the Hydrocyclone were investigated. The results from the study are summarized as follows: 1) In proportion to the increase of solid concentration, the efficiency of solid-liquid separation is improved. 2) According as the cyclone inlet pressure increases the efficiency of separation is improved. Conclusively, this research suggested that the Hydrocyclone will be used as a pre-treatment system of cooling water in ships, and eventually prevent unexpected accidents in engine systems.

• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.22-32
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• 2003

Al-brass material is generally used at the state of plastic deformation, for example; bending, extension of bell mouth at shell and tube type heat exchanger. And SCC(stress corrosion cracking) of Al-brass material will be affected by residual stress as plastic deformation. SCC results from synergism between mechanical factor and corrosion environment. Mechanical factor is stress that directly relates with stress intensity factor at the crack tip. This paper was studied on the effect of stress on SCC of Al-brass tube under in $3.5\%$ NaCl. + $0.1\%\;NH_4OH$ solution by constant displacement tester. Increasing of acidified water flow into sea and speeds up corrosion rate of Al-brass which is used as a tube material of vessel heat exchanger by polluted coast seawater. The experimental results are as follow The latent time of SCC occurrence gets longer as the initial stress intensity factor($K_{Ii}$) gets lower The main crack was propagated as the initial stress intensity factor($K_{Ii}$) gets higher, and secondary cracks occurred by electro-chemical factor a(ter stage of released stress. Dezincification phase showed around the crack, and the range of dezincification gets wider as the initial stress intensity factor($K_{Ii}$) gets higher.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.4
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• pp.401-406
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• 2017

When Liquified Natural Gas (LNG) is vaporized into NG for industrial and household usage, tremendous cold energy was transferred from LNG to seawater during phase-changing process. This heat exchanger loop is not only a waste of huge cold energy, but will cause thermal pollution to the coastal fishery area also when cold water was re-injected into the sea. In this study, an innovation design has been performed to reclaim the cold energy for -35 to $62^{\circ}C$ refrigerated warehouse. Conventionally, this was done by installing mechanical refrigeration systems, necessitating tremendous electrical power to drive temperature. A closed loop LNG heat exchangers in series was designed to replace the mechanical or vapor-compression refrigeration cycle by process simulator. The process simulation software of PRO II with provision has been used to simulate this process for various conditions, what to effect on cold energy and used energy for re-liquefaction and evaporation process. In addition, through analysis the effect of the change of LNG supply pressure on sensible and latent heat, optimum operational conditions was suggested for LNG cold energy warehouse.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.2 s.23
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• pp.109-115
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• 2005

Hydrocyclone has been widely used for the solid-liquid separation in many industrial sites because of its comparatively preferable applications that can be applied to wide-range particle sizes. If seawater with impurities flows through pumps or heat exchanger, it might cause an decrease in the efficiency of cooling system In this paper, we have suggested some methods of separating impurities from seawater in the cooling system by using a Hydrocyclone. The effects of design factors as solid concentration, cyclone inlet pressure, flow rate and diameter of underflow on the separating performance of the Hydrocyclone were investigated The results from this study are summarized as follows: 1) In proportion to the decrease of solid concentration, the efficiency of solid-liquid separation is improved. 2) According as the cyclone inlet pressure increases the efficiency of separation is improved. Conclusively, this research suggested that the Hydrocyclone will be used as a pre-treatment system of cooling water in machines, and eventually prevent unexpected accidents in engine systems.

• Proceedings of KOSOMES biannual meeting
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• 2004.11a
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• pp.109-115
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• 2004

Hydrocyclone has been widely used for the solid-liquid separation in many industrial sites because of its comparatively preferable applications that can be applied to wide-range particle sizes. If seawater with impurities flows through pumps or heat exchanger, it might cause an decrease in efficiency of cooling system. In this paper, we have suggested some methods of separating impurities from seawater in the cooling system by using a Hydrocyclone. The effects of design factors as solid concentration, cyclone inlet pressure, flow rate and diameter of underflow on the separating performance of the Hydrocyclone were investigated The results from this study are summarized as follows: 1) In proportion to the decrease of solid concentration, the efficiency of solid-liquid separation is improved 2) According as the cyclone inlet pressure increases the efficiency of separation is improved Conclusively, this research suggested that the Hydrocyclone will be used as a pre-treatment system of cooling water in machines, and eventually prevent unexpected accidents in engine systems.

• Solar Energy
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• v.17 no.4
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• pp.23-33
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• 1997

In this paper, performance of various working fluids is evaluated for the closed Ocean Thermal Energy Conversion(OTEC) power plant operating on Rankine cycle. The evaporator and condenser are modeled via UA and LMTD method while turbine and pump are modeled by specifying isentropic efficiencies. R22, Propane, Propylene, R134a, R125, R143a, R32, R410A and Ammonia are used as working fluids. Results show that newly developed fluids such as R410A and R32 that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. The superheat at the evaporator exit and subcooling at the condenser exit do not affect the performance of the simple OTEC power cycle. Turbine efficiency and heat exchanger size influence greatly the performance of the Rankine cycle. Finally, it was shown that closed OTEC power plants can practically generate electricity when the difference in warm and cold sea water inlet temperatures is greater than $20^{\circ}C$.