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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 Luman Zhao, Myung-Il Roh, Seung-Ho Ham, "Anti-sway Control of the Crane on an Offshore Support Vessel Based on the Hardware-In-the-Loop Simulation", Proceedings of ISOPE 2017, San Francisco, USA, pp. 651-654, 2017.06.25-30 file 2017-06-26
60 International Conference Ki-Su Kim, Myung-Il Roh, Ju-Sung Kim, "A Method of Dynamic Flooding Analysis in Time Domain for the Compartment Arrangement Design of a Ship", Proceedings of ISOPE 2017, San Francisco, USA, pp. 862-866, 2017.06.25-30 file 2017-06-28
59 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
58 International Conference Ki-Su Kim, Myung-Il Roh, Sung-Min Lee, "Toward a Robust Optimization Method for Ship Route Planning Considering Cost and Safety Aspect", Proceedings of ACDDE 2017, Zhangjiajie, China file 2017-08-26
57 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
56 International Conference Ki-Su Kim, Myung-Il Roh, Sung-Min Lee, Jihye Cha, Jongjin Park, DongYeon Lee, Booki Kim, "An Efficient Method for Cost and Risk Saving in Ship Route Planning", Proceedings of the 31st Asian-Pacific TEAM 2017, Osaka, Japan, 2017.09.25-28 file 2017-09-25
55 International Conference Sun-Kyung Jung, Myung-Il Roh, Seung-Min Lee, Ki-Su Kim, "Optimal Arrangement Method for Naval Surface Ship Considering the Stability, Operability, and Survivability", Proceedings of ICCAS 2017, Singapore, Singapore, 2017.09.26-28 file 2017-09-26
54 International Conference Hye-Won Lee, Myung-Il Roh, Luman Zhao, Seung-Ho Ham, Nakwan Kim, Chan-Woo Yu, "Integrated Development Environment Of Autonomic Software for USV (Unmanned Surface Vehicle) Based on Ros (Robot Operating System)", Proceedings of ICCAS 2017, Singapore file 2017-09-26
53 International Conference Jisang Ha, Myung-Il Roh, Sung-Jun Lee, Ki-Su Kim, Seung-Min Lee, "Toward Rapid Flooding Analysis of a Ship Using Surrogate Model by Deep Learning", Proceedings of the 31st Asian-Pacific TEAM 2017, Osaka, Japan, pp. 397-400, 2017.09.25-28 file 2017-09-26
52 International Conference Seong-Hoon Kim, Myung-Il Roh, Min-Jae Oh, Namkug Ku, Sehyun Myung, "Big Data Platform for PLM (Product Lifecycle Management) Systems in Shipbuilding and Offshore Industry", Proceedings of ICCAS 2017, Singapore, Singapore, 2017.09.26-28 file 2017-09-27
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