• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1053-1060
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• 2006

This paper consider an initially deformed state caused by the pressurized fluid flowing through the pipe at a constant velocity. When the initial forte is neglected in curved pipes, the natural frequencies are reduced as flow velocity increases. However, when the initial tension took into account, the natural frequencies are not changed with the change of the flow velocity. As the internal pipe pressure is increased the natural frequencies are also slightly increased. In free vibrational simulation of piping systems in petrochemical plants, it is necessary to calculate the initial state force due to the velocity and the pressure of the fluid flow from the equilibrium first, then the force should be included in the equation of motion of the systems to get more accurate natural frequencies. In this study, calculate the mass matrix and stiffness matrix of piping system by MATLAB

• Computers and Concrete
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• v.24 no.5
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• pp.445-452
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• 2019

In this paper, dynamic stress, strain and deflection analysis of concrete pipes conveying nanoparticles-water under the seismic load are studied. The pipe is buried in the soil which is modeled by spring and damper elements. The Navier-Stokes equation is used for obtaining the force induced by the fluid and the mixture rule is utilized for considering the effect of nanoparticles. Based on refined two variables shear deformation theory of shells, the pipe is simulated and the equations of motion are derived based on energy method. The Galerkin and Newmark methods are utilized for calculating the dynamic stress, strain and deflection of the concrete pipe. The influences of internal fluid, nanoparticles volume percent, soil medium and damping of it as well as length to diameter ratio of the pipe are shown on the dynamic stress, strain and displacement of the pipe. The results show that with enhancing the nanoparticles volume percent, the dynamic stress, strain and deflection decrease.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.117-125
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• 2007

This study proposes a CFD(Computational Fluid Dynamics) analysis as a method of verification of the designed-data and a supplement of the insufficient experiences in geothermal system, which shows a rapid growth among the renewable energies. The followings are the results. FLUENT 6.2.12 is used as a CFD tool on this study, with the equations of continuity, motion, energy for unsteady flow through pipes and k-epsilon turbulent model. S-type model which has one borehole with diameter 12m by depth 206m and T-type model which has 3 boreholes with $12m{\times}20m{\times}206m$ are proposed, and also the boundary conditions are described. The temperature differences between temperatures by CFD analysis and by on-site measurement are less than 1.5%, this shows a high reliability of CFD analysis process which this study proposes. After 11 days simulation operated 12 hours interval On/Off mode, it is clearly predicted that the outlet temperatures of geothermal pipes are increased by $1.2^{\circ}C$, and $2.2^{\circ}C$ after 4 months. And the outlet temperatures of geothermal pipes increased with increase of the mass flow rates through the pipes. T-type model shows that the 4m distance between boreholes are reasonable because the temperatures at 2m and 6m from boreholes are nearly same.

• Journal of Advanced Marine Engineering and Technology
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• v.14 no.4
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• pp.57-66
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• 1990

In the design of an electric power plant, the capacity to meet the peak load demand is one of the important factors to be considered. This peak load usually occurs when the most of the cooling air conditioning systems are being operated during daytime in summer season, which inevitably entails the construction of an additional electric power plant. This study is aimed to carry out a basic experiment for the development of a cooling air conditioning system using the ice energy by the surplus electric power during the night-time. The experimental apparatus consists of four major parts; (1) the heating section consisting of the air duct and I.D. fan, (2) the cold section with the ice chamber, (3) the bundle of heat pipes made in a form of the staggered arrangement with ${C_y}/{d_o}$=2.0 and ${C_x}/{d_o}$=1.73, (4) the refrigerator system to cool down the ice chamber. This study involves an intensive experiment concerning the convective heat transfer of the air flow surrounding the bundle of heat pipes. This major experimental parameters are the amount of working fluid, the velocity of air and the working temperature. The major findings of the present study are as follows; (1) The optimum amount of the working fluid necessary for the horizontal heat pipes is much more than that for the vertical type. (2) The convective heat transfer coefficients of the air are coincided with the empirical equations of Grimson and ${\breve{Z}ukauskas}$. (3) The equation of the mean heat transfer coefficient obtained in the present study is ${N_um}=0.32 {Re_max^{0.63}}$.

• Journal of Convergence for Information Technology
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• v.9 no.12
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• pp.147-156
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• 2019

Numerical study was performed to investigate the convective heat transfer of Al₂O₃/water nanofluid flowing through the concentric double pipe counterflow heat exchangers. Hot fluid flowing through the inner pipe transfers its heat to cooling fluid flowing in the outer pipe. Effects of important parameters such as hot and cold volume flow rates, fluid type in the outer and inner pipes, and nanoparticles concentration on the heat transfer and flow characteristics are investigated. The results indicated that the heat transfer performance increases with increasing the hot and cold volume flow rates, as well as the particle concentrations. When both outer and inner pipes are nanofluids with 8% nanoparticle volume concentration, nanofluids showed up to 17% better heat transfer rate than basic fluids. Also, the average heat transfer coefficient of the base fluid for annulus-side improved by 31%. Approximately 20% enhancement in the heat exchanger effectiveness can be achieved with the addition of 8% alumina particles in base fluid. But, addition of nanoparticles to the base fluid enhanced friction factor by about 196%.

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

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.10 s.115
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• pp.1050-1056
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• 2006

In this paper, a new method for the stability analysis of a pipe conveying fluid which pulsates periodically is presented. The finite element model is formulated liking into consideration of the effects of the fluid pulsating in a pipe. The damping and stiffness matrices in the finite element equation vary with time due to pulsating fluid. Coupled effects of several harmonic components in the velocity of fluid to a pipe is discussed. A new unstable region appears which will not appear in the stability analysis of single pulsating frequency. A method to directly estimate the forced response of pipe is also discussed. The results presented in this paper are verified by the time domain analysis.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1993.05a
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• pp.70-78
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• 1993

Heat pipes, applied to flat plate solar collectors, have a long and slender configuration with relatively low heat flux on the evaporator. Such a heat pipe has a tendency to build-up a liquid pool at the lower half of evaporator zone, and at this pool occurs such complicated phenomena of evaporation and fluid dynamics as superheat, sudden generation of bubble, its likely explosive growth process and flooding etc. In the present study, we tried to solve those problems by means of adjusting the two principle design parameters, liquid fill charge and wick length, using 4 heat pipes and 3 thermosyphons, with different values of parameter respectively. The corresponding results can be summarized as followings, - The thermal conductance of heat pipes was largely improved by el eliminating wick from adiabatic and condenser zone. - But on evaporator zone wick is inevitable to reduce behavior of the build -up of liquid pool , where arise diverse internal complex phenomena. - The liquid fill charge should have to be increased by 10∼20％ more than the quantity to saturate the wick.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.346-348
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• 2007

Underground pipe is an instrument to transport rapidly and safely a lot of fluid like gas, oil, water supply and drain system. It acts like blood vessels of human body in a modern industry. As in this country, the pipe facilities have been constructing since 1970's. The pipes constructed for a long time ago are already starting to reveal the problem like corrosion and most of them are built underground. So for companies, the managing of the underground pipes is very hard because it needs high technology and a lot of money. So we made a new robot system to repair and maintain the pipes at a low price. This new robot is devised using pressing wall type to work inside 700${\sim}$900(mm) size pipe. And it has good carrying and working power.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.200-204
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• 2005

A few intake stations have vibration problems caused by pumps, motors and pipes. The vibration transffered from pumps, motors and pipes excites buiding severely. Therefore, the crack is generated on building wall and people who work at intake station are damaged. In this paper, the vibration and noise have been measured and analyzed for pumps, motors, pipes and building at intake station. Also, the cause of vibration and noise is identified. Finally, the reference of vibration and noise is established using results of measurement.