• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.452-455
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• 1999

ORV which vaporizes LNG to NG is consisted of tube and header whose substrate is aluminum alloy. The corrosion of the tube is very severe because of sea water being used as the heating source. In this research to protect ORV substrate material, the corrosion behavior of aluminum alloys was investigated for the sacrificial role of Al-Zn alloy for ORV tubes. The electrochemical behavior of aluminum alloys in sea water was investigated. The corrosion behavior of thermally-sprayed and cladded samples were compared through salt spray tests. Al-Zn alloy can act as a sacrificial anode and cladded Al-Zn alloy has a better corrosion resistance than that of thermally sprayed one. The galvanic effect of Al-Zn to substrate material was conformed from scratched sample tests.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.209-218
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• 2021

First principle-based modeling studies have been performed to improve the heat exchange efficiency of ORV and optimize operation, but the heat transfer coefficient of ORV is an irregular system according to time and location, and it undergoes a complex modeling process. In this study, FNN, LSTM, and AutoML-based modeling were performed to confirm the effectiveness of data-based modeling for complex systems. The prediction accuracy indicated high performance in the order of LSTM > AutoML > FNN in MSE. The performance of AutoML, an automatic design method for machine learning models, was superior to developed FNN, and the total time required for model development was 1/15 compared to LSTM, showing the possibility of using AutoML. The prediction of NG and seawater discharged temperatures using LSTM and AutoML showed an error of less than 0.5K. Using the predictive model, real-time optimization of the amount of LNG vaporized that can be processed using ORV in winter is performed, confirming that up to 23.5% of LNG can be additionally processed, and an ORV optimal operation guideline based on the developed dynamic prediction model was presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.189-197
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• 1997

The vaporizing characteristics of LNG(liquefied natural gas) via heat exchanger with sea water are analytically studied for an open rack vaporizer(ORV). This study is intended to supply the design data for the domestic fabrication of the corrosion-resistant vaporizer tube. A computational program is developed to predict the exit temperature of LNG for various conditions. In the program, thesimple and justifiable heat transfer models are selected for fully-developed internal flow of LNG, the star-shaped finned-tube, and the external falling films of sea water, as well as the possible ice formation and the fouling on the tube walls. It is found that the enongh corrugation inside of the tube wall is the most significant in the vaporizer performance for the current operating conditions. the effects of other design parameters on the heat exchanger between LNG and sea water are quantitatively presented.

• Journal of the Korean institute of surface engineering
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• v.39 no.1
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• pp.25-34
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• 2006

Al-Mg alloy, an open rack vaporizer(ORV) material was reported to be corroded in seawater environments though the ORV material was coupled to thermally sprayed Al-Zn alloy functioning a sacrificial anode. In addition, the corrosion behavior based on the calculated corrosion potential did not match the observed corrosion behavior. Hence, the goal of this study is to get better understanding on Al or Al-Mg alloy coupled to Al-Zn alloy and to provide the calculated corrosion potential representing the corrosion behavior of the ORV material by immersion test, electrochemical tests, and calculation of corrosion and galvanic potential. The corrosion potentials of Al and Al alloys also depended on alloying element as well as surface defects. The corrosion potentials of Al and Al-Mg alloy were changed with time. In the meantime, the corrosion potentials of Al-Zn alloys were not. The corrosion rates of Al-Zn alloys were exponentially increased with zinc contents. The phenomena were explained with the stability of passive film proved by passive current density depending on pH and confirmed by the model proposed by McCafferty. Dissimilar material crevice corrosion (DMCC) test shows that higher content of zinc caused Al-Mg alloy corroded more rapidly, which was due to the fact that higher corrosion rate of Al-Zn makes [$H^+$] and [$Cl^-$] more concentrated within pit solution to corrode Al-Mg alloy. Considering electrochemical reactions within pit as well as bulk in the calculation gives better prediction on the corrosion behavior of Al and Al-Mg alloy as well as the capability of Al-Zn alloy for corrosion protection.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.67-72
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• 1998

Due to excellent corrosion resistance, in particular against sea water, Al-2wt.$\%$Zn alloys have been used as the sacrifice anode material for tube of the ORV. Al-2wt.$\%$Zn alloys thermal-sprayed coating, however, were spalled on the lower part of ORV due to the lack of bonding strength between base material and coating layer and the dropping energy of sea water, To overcome the problems of the thermal spray coating, we developed the cladded tube manufacturing process by coextrusion of the clad and base metal. The corrosion resistance of cladded tube was improved by two times at least, compared with that of the present thermal spray coated vaporizer tubes.

• Journal of the Korean Institute of Gas
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• v.23 no.1
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• pp.41-46
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• 2019

LNG is supplying to consumers as gas phase vaporized by major seawater vaporizer, i.e.. open rack vaporizers. But as soon as the temperature of seawater drops below $5^{\circ}C$ in winter, the submerged evaporators should be operated and cause a lot of energy consumption because of their natural gas combustion. In order to reduce the consumption amount, in this study new two-way supplying method of seawater instead of the present one-way supplying system is introduced and analysed the technical possibilities and economical savings. The results showed that in case of the temperature of seawater becomes below $2.5^{\circ}C$, LNG can be evaporated using ORV without operating S MV. If this system is applied in Incheon LNG terminal, the energy saving reaches 11,770 Ton of LNG as 11,760 million won. By the analysis, the two-way supplying system of seawater in ORV can be the most effective method to be able to save huge amount of energy every year.

• 한국가스학회:학술대회논문집
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• 1998.09a
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• pp.193-198
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• 1998

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1760-1764
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• 2003

This study was carried out to establish an analytical method on the open circuit seawater pipeline network for open rack vaporizers(ORVs). The linear theory method was chosen to solve this network system. In particular, the method was modified to calculate the static pressure at each node and to determine the operating condition of each pump with the mean static pressure of pumps and ORVs. The proposed method is the first report demonstrating that can be used as a solver for the complicated open circuit. Also, the method indicated the importance for exactly calculating equivalent length of pipes including valves, bends, fittings, and others to raise the accuracy. Although this technique is good for solving this system, it is still required to improve the convergence rate.

• Journal of Korean Society for Geospatial Information Science
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• v.2 no.1 s.3
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• pp.131-139
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• 1994

Geo-spatial information system technology and cartographic modeling techniques were used as a way to Improve the land use planning process. Off-road vehicle(ORV) trails, timber harvest sites, timber haul mads and wildlife ruffed grouse habitats areas should be allocated together in the Wayne National Forest in the United States. Automated spatial cartographic models were developed to resolve the conflicts of the multiple land use allocation. The techniques of descriptive and prescriptive modeling made the multiple land use allocation efficient and effective.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.45-50
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• 2001

Open rack vaporizer (ORV) has been used in liquefied natural gas (LNG) receiving terminal in order to vaporize LNG into natural gas (NG) by heat exchange with seawater The U-type ORV which had been operated with seawater for 14 years is one of the important utilities of the gas production and the weld part of tube connected with header_ pipe had experienced many corrosion problems. To elucidate the cause of corrosion at weld part of vaporizer tube, corrosion potentials were compared by parts. This study concerns on the measurement of corrosion pit depth using non-destructive method and the evaluation of stress distribution in an aspect of safety with finite element analysis. In order to confirm the reliability of galvanic corrosion between weld parts and base metal, the measurement of corrosion potential by parts was conducted for 20 minutes in 3.5$\%$(wt.) NaCl solution. Many non-destructive methods were tried to measure the remaining thickness of vaporizer tube at fields. For general corrosion, tangential radiography test was confirmed as an effective method. In case of a fine corrosion pit, the shape of corrosion pit was reproduced using surface replication method. From collected data, stress distributions were quantitatively evaluated with 2-dimensional finite element method and the diagnostic evaluation on internal pressure of the U-type vaporizer could be made.