• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.175-188
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• 2009

When a new tunnel is excavated by the drill and blast method near pre-existing underground structures or tunnels due to the region restricted condition such as urban area, the ground will be relaxed by the excavation. In this case, issues can be created in terms of stability of pre-existing underground structures. One of major factors determining the stability of pre-existing underground structures can be a separation distance between pre-existing underground structures and a newly excavated tunnel. The region of ground relaxation defined by the plastic zone due to new excavation can be varied by separation distance. In this study, in other to estimate an influence of new tunnel excavation in terms of separation distance on the stability of pre-existing large pipelines, two-dimensional scaled model tests using plaster were performed for six models which have a different separation distance, The results show that based on the analysis of induced displacement during tunnel construction, the displacement decreases as the separation distance between large pipeline and new tunnel is increased until the distance is 2.5 times of pipeline diameter. Beyond this point, however, the displacement has become stabilized.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.475-480
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• 2014

In the fields of researches associated with plant layout optimization, the main goal is to minimize the costs of pipelines for connecting equipment. However, what is the lacking of considerations in previous researches is to handle the multi floor processes considering the safety distances for domino impacts on a complex plant. The mathematical programming formulation can be transformed into MILP (Mixed Integer Linear Programming) problems as considering safety distances, maintenance spaces, and economic benefits for solving the multi-floor plant layout problem. The objective function of this problem is to minimize piping costs connecting facilities in the process. However, it is really hard to solve this problem due to complex unequality or equality constraints such as sufficient spaces for the maintenance and passages, meaning that there are many conditional statements in the objective function. Thus, it is impossible to solve this problem with conventional optimization solvers using the derivatives of objective function. In this study, the PSO (Particle Swarm Optimization) technique, which is one of the representative sampling approaches, is employed to find the optimal solution considering various constraints. The EO (Ethylene Oxide) plant is illustrated to verify the efficacy of the proposed method.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.7 no.2
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• pp.10-15
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• 2011

A ground loop heat exchanger for the ground source heat pump system is the core equipment determining the thermal performance and initial cost of the system The length and performance of the heat exchanger is dependent on the ground thermal conductivity, the operation hours, the ground loop diameter, the grout, the ground loop arrangement, the pipe placement and the design temperature. The result of this simulation shows that higher thermal conductivity of grouting materials leads to the decrease length of geothermal heat exchanger from 100.0 to 84.4%.

• Journal of the Korean Geotechnical Society
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• v.35 no.10
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• pp.5-15
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• 2019

In this study, to investigate the effect of long-term performance of energy pile on ground temperature, a numerical analysis was conducted by simulating the ground where an energy pile was installed. In the analysis, a changing distance from the outer perimeter of a heat circulation pipe to the surface of concrete pile for an intermittent operation (8-hour operation, 16-hour stop) was considered. Simulation results showed that long-term heat exchange under the intermittent operation of energy pile reduced a thermal recovery in the ground and increased the ground temperature through the residual thermal energy. In addition, the ground temperature became higher as it got closer to the energy pile and increased as the distance from the outer perimeter of heat circulation pipe to the surface of concrete pile decreased.

• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.31-39
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• 2007

Recently, the nonlinear dynamic responses among waves, submarine pipeline and seabed have become a target of analyses for marine geotechnical and coastal engineers. Specifically, the velocity field around the submarine pipeline and the wave-induced responses of soil, such as stress and strain inside seabed, have been recognized as dominant factors in discussing the stability of submarine pipeline. The aim of this paper is to investigate nonlinear dynamic responses of soil in seabed, around submarine pipeline, under wave loading. In order to examine wave-induced soil responses, first, the calculation is conducted in the whole domain, including wave field and the seabed, using the VOF-FDM method. Then, velocities and pressures, which are obtained on the boundary between the wave field and the seabed, are used as the boundary condition to compute the wave-induced stress and strain inside seabed, using the poro-elastic FEM model, which is based on the approximation of the Biot's equations. Based on the numerical results, the characteristics of wave-induced soil responses around submarine pipeline are investigated, in detail, inrelation to relative separate distance of the submarine pipeline from seabed. Also, the velocity field around the submarine pipeline is discussed.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.27-34
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• 2010

To dissipate the heat generated from the switching devices in the inverter system of HEV, the water cooling structure is proposed. The bolt type cooling structure has a problem such as water leakage for high pressure of water, therefore the proposed cooling structure applied pipe structure in the heat sink. The heat dissipation characteristics for various structures of water channel and distance between heat source and water channel was analyzed through the simulation. heat dissipation effect for two types of water cooling structures was investigated. Based on the simulation results, two types of water cooling system for 30kW inverter system of HEV were manufactured and the heat dissipation effect was verified.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.51-57
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• 2019

A plant layout problem has a large impact on the overall construction cost of a plant. When determining a plant layout, various constraints associating with safety, environment, sufficient maintenance area, passages for workers, etc have to be considered together. In general plant layout problems, the main goal is to minimize the length of piping connecting equipments as satisfying various constraints. Since the process may suffer from the heat and friction loss, the piping length between equipments should be shorter. This problem can be represented by the mathematical formulation and the optimal solutions can be investigated by an optimization solver. General researches have overlooked many constraints such as maintenance spaces and safety distances between equipments. And, previous researches have tested benchmark processes. What the lack of general researches is that there is no realistic comparison. In this study, the plant layout of a real industrial C3MR (Propane precooling Mixed Refrigerant) process is studied. A MILP (Mixed Integer Linear Programming) including various constraints is developed. To avoid the violation of constraints, penalty functions are introduced. However, conventional optimization solvers handling the derivatives of an objective functions can not solve this problem due to the complexities of equations. Therefore, the PSO (Particle Swarm Optimization), which investigate an optimal solutions without differential equations, is selected to solve this problem. The results show that a proposed method contributes to saving the capital expenditures.