• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.892-899
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• 2016

Gravity current flow past a subsea pipe above a scour based on computational fluid dynamics. For comparison, gravity current flow over pipe above a smooth bed also calculated, this configuration conventionally employed to consider the scour effect from an ideal approach. Interestingly, there different flow features and hydrodynamic forces between the scour and smooth bed cases. These results indicate that realistic conditionvery important investigatthe scour effect on gravity current flow around subsea pipe.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1225-1230
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• 2004

In this paper, the pressure drops were investigated according to the sintered porous wick structure in loop heat pipe(LHP) by theoretical analysis. LHP has the wick only in evaporator for the circulation of working fluid, so utilizes porous wick structure which pore diameter is very small for large capillary force. This paper investigates the effects of different parameters on the pressure drops of the LHP such as particle diameter of sintered porous wick, wick porosity, vapor line diameter, thickness of wick and heating capacity. Working fluid is water and the material of sintered porous wick is copper. According to the these different parameters, capillary pressure, pressure drop in wick were analized by theoretical design method of LHP.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.146-159
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• 2016

This study used Navier-Stokes Solver(LES-WASS-2D) for analyzing hydrodynamic characteristics with high order in order to analyze self-burial mechanism of pipeline with spoiler under steady flow. For the validity and effectiveness of numerical model used, it was compared and analyzed with the experiment to show flow characteristics around the pipeline with and without the spoiler. And the hydraulic(flow, vortex, and pressure) and force characteristics were numerically analyzed around the pipeline according to the incident velocity, and shape and arrangement of spoiler. Primarily, if the spoiler is attached to the pipeline, the projected area is increased resulting in higher flow velocity toward the back and strong vortex caused by wake stream in the back. Secondly, the spoiler causes vertically asymmetric flow and vorticity fields and thus asymmetric pressure field. It increases the asymmetry of force on the pipe and thus develops large downward fluid force. Both of them are the causes of selfburying of the pipeline with spoiler.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.10
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• pp.649-657
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• 2017

A rupture in a high-pressure pipe causes the fluid in the pipe to be discharged in the atmosphere at a high speed resulting in a supersonic jet that generates the compressible flow. This supersonic jet may display complicated and unsteady behavior in general. In this study, Computational Fluid Dynamics (CFD) analysis was performed to investigate the compressible flow generated by a supersonic jet ejected from a high-pressure pipe. A Shear Stress Transport (SST) turbulence model was selected to analyze the unsteady nature of the flow, which depends upon the various gases as well as the diameter of the pipe. In the CFD analysis, the basic boundary conditions were assumed to be as follows: pipe of diameter 10 cm, jet pressure ratio of 5, and an inlet gas temperature of 300 K. During the analysis, the behavior of the shockwave generated by a supersonic jet was observed and it was found that the blast wave was generated indirectly. The pressure wave characteristics of hydrogen gas, which possesses the smallest molecular mass, showed the shortest distance to the safety zone. There were no significant difference observed for nitrogen gas, air, and oxygen gas, which have similar molecular mass. In addition, an increase in the diameter of the pipe resulted in the ejected impact caused by the increased flow rate to become larger and the zone of jet influence to extend further.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5763-5768
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• 2015

A relief valve is a mechanical element to keep safety by controlling high pressure. Usually, the high pressure is relieved by using the spring force and letting the fluid to flow from another way out of system. When its normal pressure is reached, the relief valve can return to initial state. The relief valve should be designed for smooth operation and should satisfy the structural safety requirement under operating condition. The commercial software ANSYS/WORKBENCH is utilized for flow and structural analysis. Very high pressure may cause structural problem due to severe stress. The study suggests the design satisfying the structural design requirement

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1861-1871
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• 1991

In this study, the piping system conveying unsteady flow is considered. The effects of coupling between the pipe motion and the velocity and pressure of fluid are included for the dynamic stability and response analysis of the piping system. The dynamic equations for a piping system are derived by Newtonian dynamics. For the momentum and continuity equations, the concept of moving control volume is applied. Thus, the governing equations derived herein are valid for the applications to the vibration problems occurred when a piping system starts up or shuts down and also when the valves and pumps operate. For a simply supported straight pipe, the stability analysis is conducted for various nondimensional parameters. The dynamic responses, in both stable and unstable region of stability chart, are numerically tested by the use of central difference method.

• Journal of Energy Engineering
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• v.13 no.4
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• pp.267-274
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• 2004

Theoretical analysis for predicting the heat transport limitations of screen mesh wick and sintered wick heat pipes was performed. The heat pipe diameter was 8mm and water was used for working fluid. For the 250 mesh, each capillary pressures and heat transport limitations, thermal resistances were analyzed according to the operating temperatures, wick thicknesses and inclination angles, based on the effective capillary radius (r$\_$c/), porosity ($\varepsilon$) and permeability (K). The wick capillary limitation was increased as the operating temperature and the wick thickness were increased, and generally the sintered wick showed higher heat transport limitations than that of the screen wick. The thermal resistance of the screen wick was higher than that of the sintered wick and both thermal resistances were linearly increased as the wick thickness was increased.

• Journal of the Korea Convergence Society
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• v.6 no.3
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• pp.13-18
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• 2015

This paper is the study on the safe design of joint controling the pressure and temperature by connecting between pipes laying with the flexible joint. This study aims at decreasing the excessive pressure applied in the pipe and preventing the accident occurrence in order to solve the pipe damage by extraction and contraction due to the pressure of open air and transport gas. The flow properties of each model are investigated through the simulation analysis by applying three kinds of the flexible joints. When transport gas passes the flexible joint, the flow characteristics of heat, pressure and velocity at pipe laying are analyzed. It is thought to be contributed to the safe design due to the shape of the flexible joint by using the result of this study. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.1969-1975
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• 2012

The air brake system used in heavy vehicle is very important from the point of safety due to its weight. In general, air brake system generates relatively long response time and large loss of pressure. It is known that the response time can be decreased by optimal design of brake system, i.e., by increasing the system pressure, minimizing the air line, and material of components. In this study, We developed experimental rigs for the measurement of braking response of heavy duty trucks and compared with the simulated results obtained from the net work fluid flow system analysis code (FLOWMASTER). The effect of several parameters such as, system pressure, diameter of pipe, chamber temperature on the brake response performance have been examined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.999-1007
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• 2013

The present work reports numerical results of the pressure drop and heat transfer characteristics of pipes with various shapes such as circular, elliptical, circumferential wavy and twisted using a three-dimensional simulation. Numerical simulations are calculated for laminar to turbulent flows. The fully developed flow in pipes was modeled using steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations. The friction and Colburn factor of each pipe are compared with those of a circular tube. The overall flow and heat transfer calculations are evaluated by the volume and area goodness factor. Finally, the objective of the investigation is to find a pipe shape that decreases the pressure loss and increases the heat transfer coefficient.