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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
61 International Conference Min-Jae Oh, Myung-Il Roh, "Hull Form Surface Generation Using T-Spline", Proceedings of the 31st Asian-Pacific TEAM 2017, Osaka, Japan, 2017.09.25-28 file 2017-09-25
60 International Conference Min-Jae Oh, Myung-Il Roh, Sung-Woo Park, Do-Hyun Chun, In-Il Kim, Chang-Yong Kim, Won-Joon Lee, "Estimation of Ship Energy Efficiency from Big Data Analysis", Proceedings of the 32nd Asian-Pacific TEAM 2018, Wuhan, China, pp. 262-264, 2018.10.15-18 file 2018-10-17
59 International Conference Min-Jae Oh, Myung-Il Roh, Sung-Woo Park, Do-Hyun Chun, Jeong-Youl Lee, Myeong-Jo Son, "Operational Analysis of Container Ships Using AIS Data", Proceedings of ACDDE 2018, Okinawa, Japan, 2018.11.1-3 file 2018-11-01
58 International Conference Min-Jae Oh, Myung-Il Roh, Young-Soo Seok, and Sung-Jun Lee, "Optimization of a Ship Hull Form using Deep Learning", Proceedings of ACDDE 2019, Penang, Malaysia, 2019.07.07-10 file 2019-07-08
57 International Conference Myung-Il Roh, Kyu-Yeul Lee, "Generation of Production Information for a Building Block and Simulation of the Block Erection for Computer-Aided Process Planning and Scheduling", Proceedings of IMDC(International Marine Design Conference) 2006, Michigan, USA, pp. 382-395, 2006.05.16-19 file 2006-05-16
56 International Conference Myung-Il Roh, Kyu-Yeul Lee, Seong-Jin Yoo, "An Algorithm for Generating the Hull Structural Analysis Model Using the Seam Information of the Hull Structure", Proceedings of the 2nd PAAMES and AMEC 2006, Jeju, Korea, pp. 399-404, 2006.10.17-20 file 2006-10-17
55 International Conference Myung-Il Roh, Seong-Ho Seo, Hyun-Kyoung Shin, Nam-Kug Ku, Sol Ha, Ki-Su Kim, "Simplified Model for the Weight Estimation of Floating Offshore Plant Using the Statistical Method", Proceedings of OMAE 2014, San Francisco, USA, pp. 1-8, 2014.06.08-13 file 2014-06-10
54 International Conference Myung-Il Roh, Seung-Ho Ham, Ki-Su Kim, Luman Zhao, "Integrated Simulation Based on Multiphysics Analysis, Virtual Reality, and Hardware for Offshore Installation, Operation, and Maintenance", OTC Asia 2016, 2016.03.22-26 file 2016-03-23
53 International Conference Myung-Il Roh, Seung-Ho Ham, Ki-Su, Kim, Hyewon Lee, Seung-Min Lee, Luman Zhao, "Minimization of Risk in Design, Production, and Installation Process of Ships and Offshore Structures through Simulation", Proceedings of ACDDE 2017, Zhangjiajie, China file 2017-08-26
52 International Conference Myung-Il Roh, Sol Ha, Nam-Kug Ku, Seung-Ho Ham, "Multibody System Dynamics Simulator for Design and Production of Ships and Offshore Plants", Proceedings of the 28th Asian-Pacific TEAM 2014, Istanbul, Turkey, pp. 481-494, 2014.10.13-16 file 2014-10-15
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