• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.835-840
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• 2000

The objective of the present study is to investigate the characteristics of pressure wave propagation of viscous fluid flow in a circular pipe line. The goal of this study is to select the best frequency of each control factor of a circular pipe. We intend to approach a formalized mathematical model by a very exact and reasonable polynomial for fluid transmission lines. and we computed this mathematical model by computer. The results show that the oil viscosity decreased as the length of the circular pipe increases. and The energy of pressure wave propagation decreased as the pipe diameter decreases. The factor is that density of oil was changed resonant frequency. It has been found the viscosity characteristics is changed largely by length of hydraulic pipe and volume of cavity tank.

• 상하수도학회지
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• 제27권3호
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• pp.395-404
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• 2013

The risk of pipe-bursting in multi-regional transmission mains consisting of 89 % of singled pipeline is so high that pipeline stabilization project is required such as renewal and replacement, pipe paralleling, emergency ties. Pipeline stabilization projects could be postponed at the step of initial decision-making because effect of this project is intangible benefit like activation of economic, improvement of welfare related to water. This study is to suggest quantified economical feasibility model for intangible benefit presumption to solve above problem. Cost reduction of emergency water supply, leakage, burst restore and energy efficiency improvement was altered and applied. As a result of economic analysis taking into account estimated benefit and cost under discount rate 5.5 %, service life 40 years, sufficient economic feasibility analyzed with B/C 2.45, NPV 317,700 million won, IRR 9.09 %.

• 태양에너지
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• 제15권3호
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• pp.59-73
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• 1995

원활한 전력공급을 위해 지중송전케이블에서 발생된 열을 제거하기 위한 방법으로 전력구트라프간접수냉방식이 적용된 지중송전계통에 대한 각 주요 구성요소의 열해석을 수행하였다. 열해석을 수행한 결과, 주어진 조건에서 냉동기가 채택된 냉동장치에서는 냉각수유량은 $2{\sim}3{\ell}/s/pipe$, 팬에 의한 풍속은 $1{\sim}2m/s/fan$인 경우에 지중송전계통의 원활한 전력공급을 위한 냉각계통의 최적조건으로 계산되었다. 반면에 냉각탑만을 설치한 경우에는 냉각수유량 및 풍속이 각각 $2{\sim}3s/pipe$ 및 6 m/s/fan이 최적조건으로 계산되었다. 그러나 냉각탑만이 설치된 경우에는 풍속이 너무 커져서 용량이 큰 팬의 설치 및 전력구내에서 작업자의 작업조건에 적합하지 않다. 따라서 본 연구의 주어진 조건하에서 지중송전계통의 냉동계통은 냉동기가 설치된 냉동장치가 바람직하다.

• 소음진동
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• 제8권1호
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• pp.49-56
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• 1998

Although the fundamental resonance frequency of a Helmholts resonator is mainly determined by the volume of the resonator and the size of the hole, it is also affected by the position of the hole and the shape of the resonator. In this study, the inertial end corrections and the fundamental resonance frequencies of concentric pipe resonators are estimated for various positions of the hole and shapes of the resonator by using the 3-D analysis. For an effective noise reduction in concentric pipe resonators with several holes, an optimal spatial hole-distribution is proposed based on the calculated transmission loss for various hole-distributions and sizes of holes.

• 한국소음진동공학회논문집
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• 제25권8호
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• pp.559-567
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• 2015

The paper deals with an ultrasonic transducer invented for measuring both flow velocity and pipe thickness. The structure of the transducer is based on the conventional transducers for measuring flow velocity by obliquely transmitting ultrasonic waves to the flow direction. The transducer additionally generates ultrasonic waves transmitting vertically to a pipe for measuring pipe thickness. By measuring flow velocity with the invented transducer and a conventional oblique-incidence transducer and comparing their results, the accuracy of the flow velocity measurement of the invented one was evaluated. By measuring specimen thickness with the invented transducer and a conventional normal-incidence transducer and comparing their results, the accuracy of the thickness measurement of the invented one was evaluated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.386-391
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• 2001

In this paper, the vibration characteristics of IHTS(Intermediate Heat Transfer System) piping system of LMR(Liquid Metal Reactor) conveying hot liquid sodium are investigated to eliminate the pipe supports for economic reasons. To do this, a 3-dimensional straight pipe element and a curved pipe element conveying fluid are formulated using the dynamic stiffness method of the wave approach and coded to be applied to any complex piping system. Using this method, the dynamic characteristics including the natural frequency, the frequency response functions, and the dynamic instability due to the pipe internal flow velocity are analyzed. As one of the design parameters, the vibration energy flow is also analyzed to investigate the disturbance transmission paths for the resonant excitation and the non-resonant excitations.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.158-165
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• 2005

KOGAS(Korea Gas Corporation) has about a hundred of local stations to supply natural gas to the city gas companies and the power stations. As some severe flow fluctuation phenomena are observed in several governor stations, the investigation about the reasons and factors which are relating to flow fluctuation has been started. Some field surveys hav been carried out and experimental studies have been performed to find the fluctuation mechanism. As a result, it is found that the flow fluctuation is related with the length of straight pipe in front of the meter, the size of the header pipe and the variation of demand at the city gas company and the power station. Furthermore. it is also proved that both the length of the transmitter cable and the status of the coating of signal transmission cable do not affect flow fluctuation, but the measurement range of the differential pressure transmitter influences flow fluctuation. On the other hand, as the averaging the flow fluctuation is converged to less than 0.1 % in almost all of the cases, it is concluded that the quantity of flow fluctuation do not relates to metering accuracy directly.

• 한국유체기계학회 논문집
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• 제7권1호
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• pp.51-57
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• 2004

The waterhammer has recently become more important because the pumping stations were big and the systems conveying the fluid through the large and long transmission pipelines were complex. When the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity As the pressure waves are propagating between the pumping station and the distributing reservoir, the pressure inside the pipe drops to the liquid vapor pressure with the pipeline profile, at which time a vapor cavity forms, and finally the column separation occurs. If the pressure in the pipe is less than the atmospheric pressure, the pipe can be collapsed and destroyed after the water columns separated by the vapor cavity rejoin. During the reverse flow, the pressure is so abnormally increased at the pumping station that the accident of flooding may happen due to the failure of system. In this paper, the field tests on the waterhammer by the startup, stoppage, and power failure of a centrifugal pump were carried out for Yongma transmission pumping station in Seoul. The experimental results were compared with that of the numerical calculations, in which results the procedure of controlled pump normal shut-down and the two-step closing mode of controlling the ball valve for pump emergency stop are proposed to reduce the pressure surge.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.337-340
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• 2001

The suction muffler of a reciprocating compressor is used for reducing noise produced by pressure pulsations. According to the shape, the suction muffler is classified into one-chamber type, two-chamber type, Helmholtz resonator type, pipe-resonator type, and so on. These mufflers are used according to the characteristics of the frequency of compressor noise. In this study, four pole parameters have been used for calculating Transmission Loss of the muffler, and Insertion Loss has been acquired for the optimum design of the muffler by the experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.429-430
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• 2015

HVDC 송전망의 형태는 가공선로(Overhead Transmission Line)와 지중선로(Underground Transmission line)가 있다. 가공선로는 비교적 건설비가 저렴하고 쉽게 설치 할 수 있다는 장점이 있지만 설치할 부지를 확보하기 어렵다는 단점이 있다. 또한 지중선로는 설치되는 지역의 외관을 해치지 않고 주변 환경에 크게 영향을 주지 않는다는 장점이 있지만 케이블을 매설하기 위해서 깊은 관로를 파야하며 이때 많은 비용이 발생하게 된다는 단점이 있다. 새롭게 제시하는 HVDC Pipeline은 두 가지 송전망과 다른 새로운 방식으로서 도로에 Pipeline형태로 HVDC케이블을 얕게 매설하거나 지표면에 도출시키는 방식이다. 도로를 이용함으로서 가공선로의 새로운 부지를 확보해야한다는 단점을 개선하고 깊은 관로로 인해 발생하는 지중선로의 높은 공사비용을 감소시킬 수 있는 방안이라고 생각한다.