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Abstract The dual mixed refrigerant (DMR) cycle, which pre-cools natural gas with the mixed refrigerants and then liquefies the natural gas with another set of mixed refrigerants, is well known for having the highest efficiency among the liquefaction cycles. Its possible application to LNG FPSO is also extensively investigated. In this study, the optimal operating conditions, such as the equipment's flow rate, pressure, temperature, and refrigerant composition per flow of the DMR cycle, were determined in consideration of power efficiency. To determine the optimal operating conditions, a mathematical model was formulated based on the mathematical model of the single mixed refrigerant (SMR) cycle with additional consideration of tees, phase separators, and common headers. In the mathematical model, the 227 operating conditions were defined as unknowns and 196 equality constraints related to the thermodynamics for the equipment were formulated. Further, the 15 given variables related to the natural gas, compressor efficiency and seawater coolers were used. This mathematical model can be regarded as the optimization problem, in which the number of unknowns is larger than the total number of equality constraints and given variables. To obtain the optimal operating conditions, the minimization of the required power for the compressors at the cycle was defined as an objective function. Moreover, set as design variables were the 16 operating conditions, such as flow rate, pressure, temperature and composition of the main and precooling refrigerant, natural gas temperature after precooling, and flow rate ratio for the tee. In addition, the temperature conditions for the equipment’s operation were used as inequality constraints. The optimal operating conditions were then obtained by using a hybrid optimization method that consists of the genetic algorithm (GA) and sequential quadratic programming (SQP). The calculation results show that the required power at the obtained conditions was decreased by 34.5% compared with that of the relevant patent obtained in 2001, and 1.2% compared with the corresponding value from the past relevant study carried out in 2008.
Publication Date 2011-06-19

Kyu-Yeul Lee, Ju-Hwan Cha, Joon-Chae Lee, Myung-Il Roh, Ji-Hyun Hwang, "Determination of the Optimal Operating Condition of Dual Mixed Refrigerant Cycle at the Pre-FEED Stage of LNG FPSO Topside Liquefaction Process", Proceedings of ISOPE(International Society of Offshore and Polar Engineers) 2011, Maui, USA, pp. 151-158, 2011.06.19-24


List of Articles
번호 분류 제목 Publication Date
21 International Conference Ki-Su Kim, Myung-Il Roh, "Optimization of the Arrangement Design of a Ship Considering the Multiple Performance", Proceedings of ACSMO 2020, Seoul, Korea, pp. 167, 2020.11.23-25 file 2020-11-24
20 International Conference Jisang Ha, Myung-Il Roh, Hye-Won Lee, Jong-Ho Eun, Jong-Jin Park, Hyun-Joe Kim, "A Method of the Collision Avoidance of a Ship Using Real-time AIS Data", Proceedings of ACSMO 2020, Seoul, Korea, pp. 106, 2020.11.23-25 file 2020-11-23
19 International Conference Hye-Won Lee, Myung-Il Roh, Seung-Ho Ham, "Method for the Accurate and Automatic Operation of Offshore Floating Cranes for the Block Erection in Shipyards", Proceedings of OMAE 2020, Held in Virtual Conference, 2020.08.03-07 file 2020-08-05
18 International Conference Ki-Su Kim, Myung-Il Roh, Seung-Ho Ham, Sol Ha, "An Improved Method for the Evacuation Analysis of a Passenger Ship Considering Intermediate Flooding", Proceedings of PRADS 2022, Dubrovnik, Croatia, 2022.10.09-13 2022-10-09
17 International Conference Jisang Ha, Myung-Il Roh, Ki-Su Kim, Min-Chul Kong, "Integrated Method for the Arrangement Design of a Ship for Implementing Digital Twin in Design", Proceedings of PRADS 2022, Dubrovnik, Croatia, 2022.10.09-13 file 2022-10-10
16 International Conference Jin-Hyeok Kim, Myung-Il Roh, In-Chang Yeo, Ki-Su Kim, Min-Jae Oh, Sejin Oh, "Estimation Model of Hydrodynamic Performance Using Hull Form Variation and Deep Learning", Proceedings of PRADS 2022, Dubrovnik, Croatia, pp.??, 2022.10.09-13 2022-10-09
15 International Conference Min-Chul Kong, Myung-Il Roh, Jisang Ha, Eun Seok Jin, Donghun Yu, "Design of the Integrated System for the Safe Operation Based on Augmented Reality", Proceedings of PRADS 2022, Dubrovnik, Croatia, 2022.10.09-13 2022-10-12
14 International Conference Do-Hyun Chun, Myung-Il Roh, Hye-Won Lee, Seung-Ho Ham, "A Method for Automatic Control of Cranes for Block Lifting in Shipyard", Proceedings of PRADS 2022, Dubrovnik, Croatia, pp. 64, 2022.10.09-13 file 2022-10-09
13 International Conference Do-Hyun Chun, Myung-Il Roh, Hye-Won Lee, "Deep Reinforcement Learning-Based Ship Collision Avoidance Considering Collision Risk", Proceedings of TEAM 2022, Istanbul, Turkey, pp. 268, 2021.12.06-07 file 2021-12-07
12 International Conference Jeong-Ho Park, Myung-Il Roh, Hye-Won Lee, Jisang Ha, Yeong-Min Jo, Nam-Sun Son, "Detection and Tracking Methods of Maritime Obstacles Using Multiple Cameras", Proceedings of ICDM 2022, Siheung, Korea, 2022.04.28-29 2022-04-28
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