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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
30 International Conference Seung-Ho Ham, Myung-Il Roh, Hye-Won Lee, "Lifting Design for Ships and Offshore Structures Using Non-interpenetration Constraints and Flexible Multibody System Dynamics", Proceedings of ISOPE 2018, Sapporo, Japan, pp. 910-913, 2018.06.10-15 file 2018-06-11
29 International Conference Seung-Ho Ham, Myung-Il Roh, Hye-Won Lee, "Physics-based Simulation and Its Applications for Design, Production, and Installation of Ships and Offshore Structures", Proceedings of SUTTC 2017, Haikou, China, pp. 1, 2017.11.23-24 file 2017-11-24
28 International Conference Seung-Ho Ham, Myung-Il Roh, Hye-Won Lee, Dong-Hoon Jeong, "Physics-based Simulation Considering Collision During Production and Installation of Ships and Offshore Plants", Proceedings of ICCGS 2016, Ulsan, Korea, 2016.06.15-18 file 2016-06-16
27 International Conference Seung-Ho Ham, Myung-Il Roh, Hye-Won Lee, Jeong-Woo Hong, "Multi-physics Simulation Framework for Design and Production of Ships and Offshore Plants", Proceedings of PRADS 2016, Copenhagen, Denmark, 2016.09.04-09.08 file 2016-09-07
26 International Conference Seung-Ho Ham, Myung-Il Roh, Jong-Hyuk Lee, Sung-Jun Lee, "Multi-purpose Simulator for Ships and Offshore Structure", Proceedings of ACDDE 2018, Okinawa, Japan, 2018.11.1-3 file 2018-11-01
25 International Conference Seung-Ho Ham, Myung-Il Roh, Ki-Su Kim, Luman Zhao, Sol Ha, "Integrated Simulation Framework Based on Multibody Dynamics, Realistic Visualization, and Hardware for Shipbuilding Production and Offshore Installation", Proceedings of MARSIM 2015, UK file 2015-09-10
24 International Conference Seung-Ho Ham, Myung-Il Roh, Luman Zhao, Sol Ha, "Drillship Simulation Based on the Integration of Motion Analysis, Virtual Reality, and Motion Platform", Proceedings of TEAM 2015, Vladivostok, Russia, 2015.10.12-15 file 2015-10-13
23 International Conference Seung-Ho Ham, Myung-Il Roh, Xing Li, Luman Zhao, "Collaborative Simulation of the Block Turn-over Operation Based on Multibody System Dynamics and Virtual Reality", Proceedings of SUTTC 2015, Bejing, China, 2015.10.23-25 file 2015-10-24
22 International Conference Seung-Min Lee, Myung-Il Roh, Ki-Su Kim, Seung-Ho Ham, "Optimization of Tugboats Operation for Transporting an Offshore Floating Crane in Environmental Disturbance", International Conference on Mechanical Design and Engineering, 2017.01.20-22 file 2017-01-21
21 International Conference Sol Ha, Ki-Su Kim, Seung-Ho Ham, Myung-Il Roh, Nam-Kug Ku, "Co-simulation of Multibody System Dynamics and Moving Particle Semi-implicit Method for Heavy Load Lifting Operations in Shipyards", Proceedings of ISOPE 2015, Hawaii, USA, 2015.06.21-26 file 2015-06-25
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