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Effect of Pressure Drop on Performance of Hollow - Fiber Membrane Module for Gas Permeation
Chang, Daejun,Min, Joonho,Oh, Sehern,Moon, Kiho 한국화학공학회 1998 Korean Journal of Chemical Engineering Vol.15 No.4
The pressure drop mainly due to viscous friction inside hollow fibers is taken into consideration by nondimensionalization and numerical simulation of governing equations. For pure gas, the permeation pressure and velocity of actual situations with a viscous fluid deviate significantly from those, of the corresponding inviscid or nopressure-drop cases. The apparent permeability estimated from the, relation of permeate flow rate and pressure difference is considerably underestimated in actual situations, and more severely for the region of small pressure difference and large module length. Numerical simulation shows that the estimated permeability behaves as if it were an increasing function of pressure difference tar a constant permeability and roughly a constant for a dual-sorption-type permeability, respectively. For binary-mixture permeation the cut ratio and purity of permeate stream are mainly governed by two dimensionless parameters standing for pressrue drop and permeability, respectively. The cut ratio and corresponding product composition are predictable without the rigorous simulation of the governing equations.
Chang, Daejun,Han, Sang Heon,Yang, Kyung-Won Techno-Press 2012 Ocean systems engineering Vol.2 No.1
This study revealed the behavior of droplets formed through leak process in deep water. There was a threshold depth named the universal attraction depth (UAD). Droplets rose upward in the zone below the UAD called the rising zone, and settled down in the zone above the UAD called the settling zone. Three mass loss modes were identified and formulated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. The first two were active for the settling zone, and all the three were effective for the rising zone. In consequence, the life time of the droplets in the rising zone was far shorter than that of the droplets in the settling zone.
FPSO Cargo Pumping 시스템 가상운전 시스템 개발
남기일(Kiil Nam),한기훈(Kihun Han),장광필(Kwangpil Chang),오태영(Taeyoung Oh),장대준(Daejun Chang),송석용(Seokryong Song) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
This study developed the virtual operation system for the hydraulic pump system for marine usage. The scope of this study is to develop a process dynamic simulation model for the hydraulic pump system for marine usage, to investigate the process dynamic characteristics using the models, to accomplish the logic diagram for the PLC control and to achieve a human-machine interface (HMI) for the convenience of operators to monitor and control the process. The virtual operation system provides a virtual operation environment for the pumping system, enabling the operators to simulate the change of process variables. The system will assist in developing advanced control logics and then optimal design of the system.
Choung, Choungho,Chang, Daejun Elsevier 2018 Ocean engineering Vol.149 No.-
<P><B>Abstract</B></P> <P>This paper presents a new approach to the structural availability quantification of a slender beam element affected by external random loads with a special focus on yield strength. The proposed method introduces the concept of structural availability, which is intrinsically identical to the concept of operational availability in system reliability engineering. Structural availability is formulated with structural failure and repair models. The failure model is determined based on failure probability and the Poisson approximation. In applying the structural availability method to design, it is possible to quantitatively measure features related to the operation and maintenance of structures and to identify cost-effective design options. To understand feasibility levels of structural availability, two cases based on actual design data are examined using the proposed method. The case study results illustrate not only processes of quantifying the structural availability of a beam element but also the cost-effectiveness evaluations on specific design options.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The concept of structural availability is suggested for a slender beam's yield strength. </LI> <LI> Structural availability is quantified using structural failure and repair models. </LI> <LI> Structural failure model is defined from failure probability and the Poisson approximation. </LI> <LI> Two examples are examined for presenting potential advantages of structural availability. </LI> <LI> Based on structural availability, an optimized design option with sufficient safety and cost-effectiveness can be determined. </LI> </UL> </P>