• 설비공학논문집
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• 제3권1호
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• pp.26-33
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• 1991

An experimental study has been performed on the heat transfer by the natural convection from a conducting tube with two axial fins to a surrounding cylinder. In case of vertical fins, the maximum local Nusselt number of conducting tube appears at ${\theta}{\fallingdotseq}145^{\circ}$ and that of outer cylinder appears at ${\theta}=0^{\circ}$, for $l_F=0.3$. In case of horizontal fins, the maximum local Nusselt number of conducting tube appears at ${\theta}=180^{\circ}$ and that of outer cylinder appears at ${\theta}=0^{\circ}$. The local Nusselt number of the upper fin and the downward fin shows negative values for $l_F=1.0$. The local Nusselt number of the lower fin and the downward fin shows higher values than that of the upper fin and the upward fin. The mean Nusselt number of conducting tube in case of vertical fins are increased in order of $l_F=0.6$, 0.3, 1.0 and 0.0, but in case of horizontal fins, in order of $l_F=1.0$, 0.6, 0.3, and 0.0. The mean Nusselt number of outer cylinder in case of vertical fins are increased in order of $l_F=1.0$, 0.0, 0.3 and 0.6, but in case of horizontal fins, in order of $l_F=0.6$, 1.0, 0.3, and 0.0.

• Journal of Advanced Marine Engineering and Technology
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• 제29권4호
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• pp.417-425
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• 2005

An experimental study is performed on the turbulent swirling flow behind a crcular cylinder using 2-D PIV technique. The Reynolds numbers investigated are 10.000, 15,000. 20.000 and 25.000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the cylinder along the test tube. A comparison is included without swirling flow behind a circular and square cylinder. The recirculation zones are shown unsymmetric profiles.

• 한국소음진동공학회논문집
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• 제17권6호
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• pp.498-506
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• 2007

Using wind tunnel, experimental approaches were employed to investigate fluidelastic instability of tube bundles, subjected to uniform cross flow. There are several flow-induced vibration excitation mechanisms, such as fluidelastic instability, periodic wake shedding resonance, turbulence-induced excitation and acoustic resonance, which could cause excessive vibration in shell-and tube heat exchanges. Fluidelastic is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to cross flow. The system comprised of cantilevered flexible cylinder(s) and rigid cylinders of normal square array, In order to see the characteristics of flow in tube bundles, particle image velocimetry was used. From a practical design point of view, Fluidelastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping. The threshold flow velocity for dynamic instability of cylinder rows is evaluated and the data for design guideline is proposed for the tube bundles of normal square array.

• 한국산업융합학회 논문집
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• 제6권3호
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• pp.253-259
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• 2003

An experimental study was performed for turbulent flow behind a circular and a square cylinder by using 2-D PIV(Particle Image Velocimetry) technique in a cylindrical tube. The Reynolds number investigated were 10,000, 30,000 and 50,000. The measuring system consists of CCD camera. Ar-ion laser, image grabber and a host computer. The mean velocity vector, time mean axial velocity, turbulent intensity and Reynolds shear stress were measured along the test tube. The results are compared each other for the circular and the square cylinder.

• 오토저널
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• 제13권3호
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• pp.32-42
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• 1991

In SI engine research the pressure data in cylinder is the most important fundamental ones leading to engine efficiencies and performances. It is, therefore, necessary to obtain accurate pressure data and yet it is often impossible to install a reliable data producing, flush-mounted type pressure transducer in a cylinder of small and medium size multicylinder SI engines. When flush mounting the transducer is not possible, the spark-plug type pressure transducer is commonly used as an alternative. In this case, the transmission tube of spark-plug type pressure transducer introduces distortions in the pressure signal. Efforts were made to understand the dynamic characteristics of spark-plug pressure transducer by shock tube tests and real engine experiments. In engine experiment the cylinder pressure data were simultaneously obtained by both flush mounted and spark-plug type pressure transducers of certain transmission tube geometry. Those pressure data collected by spark-plug type pressure transducer were tested for correction to flush mounted ones by the application of transfer function. As a result of the calibration the IMEP difference between F/M data and improved S/P data was shown to be corrected about 75-98% from the original ones.

• 대한기계학회논문집B
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• 제33권2호
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• pp.124-132
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• 2009

Experiments have been performed to investigate fluid-elastic instability of tube bundles, subjected to twophase cross flow. Fluid-elastic is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and the threshold flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.6641-6646
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• 2015

배열회수 보일러의 전열관군은 외부에 가스터빈에서 나온 고온의 배기가스가 흐르게 된다. 이러한 유체의 흐름으로 인해 전열관군에서 시간변화에 따라 양력의 변동이 발생하는데 이에 따라 유동 유발 진동이 발생한다. 이러한 진동이 배열회수 보일러의 전열관군에서 파손을 야기할 수 있어서 열교환기의 구조적 안정성을 위해 열교환기의 전열관군에서 유동 유발 진동 특성을 규명할 필요가 있다. 일반적인 열교환기 전열관군에서 유동 유발 진동에 관한 실험적 연구는 기존에 많이 진행되어 오고 있으며 유동 유발 진동에 대한 무차원 PSD(Power Spectral Density) 함수를 무차원 주파수인 Strouhal 수, fU/U의 함수로 실험적 결과들이 도출되어 있다. 본 연구는 열교환기 전열관군에서 유동 유발 진동에 관한 기존의 실험적 연구들의 결과를 전산유체해석을 통해 검증하고 배열회수 보일러의 전열관군의 유동 유발 진동 특성에 적용하기 위한 기반을 마련하는 것을 목적으로 한다. 이러한 것을 위해 기존 연구에서 실험에 사용한 전열관군에서 비정상 상태 유동해석을 수행하여 전열관군에서의 양력 변화 특성을 살펴보았다. 또한 전열관군에서 양력 변동 특성으로부터 유동 유발 진동에 따른 PSD 특성 결과를 도출하여 기존의 연구들과 비교를 통해 전열관군에서의 PSD 특성을 정립하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제27권6호
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• pp.753-758
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• 2003

In this study. an experiment has been performed to investigate distributions of static pressure around a circular cylinder in a uniform shear flow which is made by a specially designed wind tunnel. From the computation program(BLAYER), various boundary layer value are obtained depending on the shear flow rate. It is basical design data that boundary layer flow phenomenon of nuclear power plant heat exchanger tube surroundings. airfoil. and others flow fields.

• 동력기계공학회지
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• 제20권6호
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• pp.34-39
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• 2016

This paper is the numerical study on the correlation of leakage by the variation of inlet pressure and clearance in hydrostatic bearing. The main goal of this study is to apply to the design of hydro system the results that the pocket pressure and the leakage rate according to the inlet pressure and the clearance between piston and cylinder tube. Because the hydrostatic bearing in hydraulic cylinder has the narrow rectangular channel between piston and cylinder tube, so to verify the numerical scheme, it has been compared with the experimental results of Brackbill and Kandlikar. The pressure data of numerical results inside narrow rectangular channel correlate was showed a good agreement with experimental results, thereby the numerical scheme was applied to the real model that is a hydraulic cylinder with the hydrostatic bearing. In conclusion, the pressure differences between inlet and pocket were shown within 3%. Leakage rates were showed rapidly increased pattern between about 4.5 and 6.7 times because the section area to calculate the leakage rates were proportioned to a square of diameter. The correlation equation was calculated among the inlet pressure, the clearance and the leakage rate by using the linear regression.

• 소성∙가공
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• 제18권5호
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• pp.385-391
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• 2009

An adhesively bonded power steering cylinder with a steel tube and an aluminum bracket was developed to reduce the weight of steering systems. To achieve the joint strength between the steel tube and of the aluminum bracket, the shape aluminum bracket re-designed by using the FE-analysis. Fracture behavior of the adhesive layer was considered by a cohesive zone model(CZM), which is based on the two-parameter fracture phenomenon with critical stress and fracture toughness. From the result of FE-analysis with CZM, re-designed power steering cylinder satisfied the desired joint strength for axial and torsion modes. And its joint strength was verified by the fracture test in each mode.