• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.581-584
• /
• 2008

At the inlet and outlet differential pressure and The fluid velocity over 32m/s are damaged (Plug, sheet ring, trim) About reduction trim parts of the control valve. AOV of the differential pressure 1,500psi become often the damage in the nuclear power plant. Damages of AOV studied CFD analysis and improvement program. Multi-stage trim designs which decrease a fluid kinetic energy are demanded and AOV parts are demanded case hardening and material change.

• Journal of the Society of Disaster Information
• /
• v.17 no.1
• /
• pp.1-9
• /
• 2021

Purpose: The purpose of this study is to analyze the differential pressure and velocity to prevent smoke backflow of Stairways Apartment House fire, and verified the effectiveness of smoke velocity standards proposed by NFSC 501A. Method: The smoke control design of the stairways apartment house of the real model and the performance of the velocity to prevent smoke backflow according to the window opening conditions of the living room were analyzed using the CONTAM program. Result: Although the differential pressure performance of the apartment's smoke control system was satisfactory, it was found that Performance of velocity to prevent smoke backflow did not come out according to the opening condition of the living room window. Conclusion: In the case of Stairways Apartment House, it is necessary to review the method of making exceptions to the 'velocity to prevent smoke backflow' standard required by the National Fire Safety Codes(NFSC 501A)

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.6
• /
• pp.110-116
• /
• 1998

For the vibration analysis of 3-dimensional piping system containing fluid flow, a transfer matrix method is presented. The fluid velocity and pressure were considered, that coupled to longitudinal and flexural vibrations. Transfer matrices and point matrices were derived from direct solutions of the differential equations of motion of pipe conveying fluids, and the variations of natural frequency with flow velocity for 3-dimensional piping system were investigated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 1998.11a
• /
• pp.232-235
• /
• 1998

Air sparging system is a kind of in-situ bioremediation method in the contaminated ground water. When Air sparging, the both of water circulation and oxygen transfer happend in the same time. The hydraulic differential head is zero at the middle height of well, is negative below the height and is possitive above the height. Hydroraulic head gradient is proportioned to air superficial velocity in the well. But over 24m/min of the superficial velocity, the hydraulic head gradient increase little.

• Solar Energy
• /
• v.5 no.2
• /
• pp.54-59
• /
• 1985

Due to the grainboundary recombination and the poor diffusion length, the polycrystalline cell efficiency is lower than the singlecrystalline cell. In order to define the effect of grains and grain-boundaries, 2 - dimensional differential diffusion equations of minority carrier are modelled. To solve them, two theoretical formulas are derived, which can be evaluated the grainboundary recombination velocity and the grain diffusion length. Also computer-aided numerical analysis is given.

• Proceedings of the KAIS Fall Conference
• /
• 2003.06a
• /
• pp.288-290
• /
• 2003

Artificial heart is divided by pulsation flow type and continuous flow type according to blood circulation pattern. Axial flow blood pump is a kind of continuous flow type artificial heart. Axial flow blood pump would be different pump performance according to impeller's shape and rotating velocity. Pump performance be able to compare by flow rate according to differential pressure and Impeller's rotating velocity. It confirms Impeller model of better efficiency according to compare Pump performance of axial flow blood pump using CFD with actual experiment result.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.4
• /
• pp.352-357
• /
• 2004

This paper studies the errors that associated with particle velocity and intensity in a space. We theoretically derived their bias error and random error. The analysis shows that the more samples do not always guarantee the better results. The random error of the velocity and intensity are increased when we have many samples. The characteristics of the amplification of the random error are analyzed in terms of the sample spacing. The amplification was found to be related to the spatial differential of random noise. The numerical simulations are performed to verify theoretical results.

• Wind and Structures
• /
• v.25 no.4
• /
• pp.381-395
• /
• 2017

Nonlinear vibration and instability of cylindrical shell conveying fluid-nanoparticles mixture flow are studied in this article. The surrounding elastic medium is modeled by Pasternak foundation. Mixture rule is used for obtaining the effective viscosity and density of the fluid-nanoparticles mixture flow. The material properties of the elastic medium and cylindrical shell are assumed temperature-dependent. Employing first order shear deformation theory (FSDT), the motion equations are derived using energy method and Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The effects of different parameters such as volume percent of nanoparticles, boundary conditions, geometrical parameters of cylindrical shell, temperature change, elastic foundation and fluid velocity are shown on the frequency and critical fluid velocity of the structure. Results show that with increasing volume percent of nanoparticles in the fluid, the frequency and critical fluid velocity will be increases.

• Journal of The Korean Astronomical Society
• /
• v.25 no.2
• /
• pp.67-78
• /
• 1992

Effects of cloud rotation 011 the profiles of CO J=$1{\rightarrow}0$ lines arc investigated by theoretically general ing line profiles under physical conditions similar to t he ones in large globules. The synthesized profiles are presented and their characteristics are discussed. It is found that when the Doppler shift of the observed CO lines is interpreted as the rotation velocity, the optically thin $^{13}CO$ lines underestimate the rotation velocity by up to 10 percents, while the self-reversed optically thick $^{12}CO$ lines overestimate the velocity up to 20 percents. The optically thin line is shown to be of use in probing the distribution of rotation velocity in dark globules.

• Computers and Concrete
• /
• v.21 no.5
• /
• pp.569-582
• /
• 2018

In this study, nonlinear vibration and stability of a polymeric pipe reinforced by single-walled carbon naotubes (SWCNTs) conveying fluid-nanoparticles mixture flow is investigated. The Characteristics of the equivalent composite are determined using Mori-Tanaka model considering agglomeration effects. The surrounding elastic medium is simulated by orthotropic visco-Pasternak medium. Employing nonlinear strains-displacements, stress-strain energy method the governing equations were derived using Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The influence of volume percent of SWCNTs, agglomeration, geometrical parameters of pipe, viscoelastic foundation and fluid velocity are shown on the frequency and critical fluid velocity of pipe. Results showed the increasing volume percent of SWCNTs leads to higher frequency and critical fluid velocity.