• 동력기계공학회지
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• 제4권3호
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• pp.19-24
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• 2000

This study concerns the performance of the heat transfer of the thermosyphon having 80 internal groove in which boiling and condensation occur. Distilled water has been used as a working fluid. The liquid filling as the ratio of working fluid volume to total volume of thermosyphon has been used as the experimental parameters. The heat flux and heat transfer coefficient at the condenser are estimated from the experimental results. The experimental results have been assessed and compared with the existing theories. As a result of the experimental investigation, the maximum heat flow rate in the thermosyphon is proved to be dependent upon the liquid fill quantity. relatively high rates of heat transfer have been achieved operating in the thermosyphon with the internal groove. Also, a thermosyphon with the internal groove can be used to achieve some inexpensive and compact heat exchangers in low temperature. In addition, overall heat transfer coefficients and the characteristics as an operating temperature are obtained for the practical applications.

• 동력기계공학회지
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• 제16권1호
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• pp.12-18
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• 2012

The fluid performance is one of the key design factors considered during the development of torque converters especially at conceptual design stages. Therefore the design environment that allows an easy access to legacy data of fluid performance could be critical to reduce the design life cycle as well as to increase the performance of the torque converter. In this paper we present a computer-based system that enables designers to utilize massive legacy data for their design of torque converters. For the implementation of the system we propose a standard format for the legacy data and build them into the database to be efficiently shared by designers in the company. Also we provide numerous analysis tools in the system that allow, for example, database management, data viewing and document generation for search, analysis and reporting. In the paper the implementation of the system is introduced in detail with its effective user interface.

• 동력기계공학회지
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• 제16권2호
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• pp.30-35
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• 2012

The geothermal energy is one of the renewable energy sources which can contribute in accomplishing a vision and goal of the national plan on energy for a government suggestion. Especially, the geothermal energy is evaluated as the nearly unlimited resources. The yearly underground temperature distribution by depth is very important to the design of air-conditioning system which uses a geothermal energy. Furthermore, there has no data for comparisons to numerical analysis. In this study, the yearly underground temperature is measured under the depth of 2 m in Tongyeong, and these data are compared with numerical analysis results for checking the accuracy. The results showed that the experimental temperature and numerical results had a good agreements and these results will be utilized to predict a performance of air-conditioning system for using a geothermal energy.

• 동력기계공학회지
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• 제16권1호
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• pp.65-71
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• 2012

A numerical procedure is described for predicting the dynamic structural responses of tension leg platforms(TLPs) in current and waves. The developed numerical approach is based on a combination of the three dimensional source distribution method and the dynamic structural analysis method, in which the superstructure of the TLPs is assumed to be flexible instead of rigid. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in the dynamic structural analysis. The equations of motion of a whole structure are formulated using element-fixed coordinate systems which have the origin at the nodes of the each hull element and move parallel to a space-fixed coordinate system. The dynamic structural responses of a TLP were analyzed in the case of including the current or not including the one in waves and the effects of current on the TLP were investigated.

• 동력기계공학회지
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• 제16권1호
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• pp.44-50
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• 2012

팁 간격의 크기가 냉각탑용 축류팬의 성능과 누설 유동에 미치는 영향을 조사하기 위해서 서로 다른 2가지 팁 간격을 가진 경우에 대해서 점성유동을 해석하였다. 케이싱 내에서 작동하는 축류팬 주위의 유동을 연속방정식, Navier-Stokes 방정식 등을 지배방정식으로 사용하여 수치해석 하였다. 난류유동에 나타나는 레이놀즈 응력은 ${\kappa}-{\epsilon}$ 난류모델을 사용하여 계산하였다. 전체적으로 H형 격자계를 사용하였으며, 팁 주위의 유동을 해석하기 위해서 팁 영역 주위에 부분적으로 조밀한 격자를 두었다. 팁 간격이 증가하면 누설 유동의 증가로 인한 유동 손실의 증가로 전압상승과 수력효율이 감소하였다. 팬 직경에 대한 팁 간격이 0.4%에서 1.0%로 증가하면 전압상승 값이 약 10% 정도 감소하였으며, 수력효율은 약 3% 정도 감소하였다. 팁 간격이 팁 근처 날개 주위의 압력에 미치는 영향을 보면, 팁 간격이 증가하여 누설 유동이 증가하면 흡입면과 압력면의 압력차가 전연 부근에서 감소함을 알 수 있었다. 누설 와류의 중심은 코드를 따라서 흡입면으로 부터 떨어져 나가면서 형성됨을 알 수 있었다. 누설 와류의 위치를 보면 팁 간격이 증가하면 와류 중심의 위치가 흡입면 쪽으로 이동하고, 흡입면에서 떨어진 거리도 날개 후반부에서 증가 폭이 커지는 포물선 형태로 증가함을 알 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.80-85
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• 2002

A conveying fluid cantilever pipe system subjected to an uniformly distributed tangential follower force and three moving masses upon it constitute this vibrational system. The influences of the velocities of moving masses, the distance between two moving masses. and the uniformly distributed tangential follower force have been studied on the dynamic behavior of a cantilever pipe system by numerical mettled. The uniformly distributed tangential follower force is considered within its ciritical value of a cantilever pipe without moving masses, and three constant velocities and three constant distance between two moving masses are also chosen. When the moving masses exist on pipe, As the velocity of the moving mass and distributed tangental force increases, the deflection of cantilever pipe conveying fluid is decreased, respectively. Increasing of the velocity of fluid flow make the amplitude of cantilever pipe conveying fluid decrease. After the moving mass passed upon the pipe, the tip displacement of pipe is influenced by the potential energy of cantilever pipe.

• 동력기계공학회지
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• 제19권4호
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• pp.36-42
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• 2015

TMixed convective flow in a bottom heated and top cooled rectangular channel can be significantly affected by the channel aspect ratio, Prandtl number, Reynolds number, Rayleigh number and angle of inclination. In such a mixed convection, the flow pattern plays an important role in various technological processes. In this study, a numerical investigation is carried out to explore mixed convection in a three-dimensional rectangular channel with bottom heated and top cooled uniformly. The three-dimensional governing equations are discretized using the finite volume method. In the range of low Reynolds number($0{\leq}Re{\leq}9.6{\times}10^{-2}$), the effects of the aspect ratio($2{\leq}AR{\leq}12$) and Gr/Re are presented and discussed. The longitudinal roll number in the channel is increased with increasing aspect ratio, and the roll number induced, regardless of the aspect ratio number, is even in the range of aspect ratios between 2 and 12, New vortex flow structure containing inclined longitudinal rolls is found, which is affected by aspect ratio and Reynolds number. The ratio Gr/Re is used to check the relative magnitudes of forced and natural convection in the mixed convective flow of high viscous fluid.

• 한국생산제조학회지
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• 제20권6호
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• pp.805-810
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• 2011

Recently, Use of Auxiliary power unit(APU) is increasing by growing demand for improvement of insufficient electric power and installation of emergency generation devices in military tracked vehicles and civil markets. And the trend is that the units are demanded for smaller size, lighter weight and higher output power, etc to suit consumer demands. To achieve these, it is essential to develop high performance system. Therefore, in this study, it was conducted in numerical analysis to investigate flow characteristics of rotor in APU generator. Also output performance of APU applied on the rotor is analyzed by experimental method. As the result, higher rotating speed of rotor caused high air flow rate at suction and it leads to linear increase of discharging flow rate. The maximum theoretical power was achieved at 12 $m^3$/min of flow rate and, at that time, output power of generator was about 7.825 kW. Also, it can be confirmed the stabilization of output performance is achieved in about 2 seconds by experiment.

• 동력기계공학회지
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• 제9권4호
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• pp.65-70
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• 2005

A liquid storage rectangular tank structures are used in many fields of civil, mechanical and marine engineering. Especially, Ship structures have many tanks in contact with inner or outer fluid, like ballast, fuel and cargo tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tank structures. Many authors have studied vibration of cylindrical and rectangular tanks structures containing fluid. Few research on dynamic interaction among tank walls through fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass have to be considered. In the present paper, coupling effect between panels of tank structure on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region have investigated numerically and experimentally.

• 동력기계공학회지
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• 제18권3호
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• pp.79-86
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• 2014

Mixed convective vortex flow in the three-dimensional rectangular channel filled with high viscous fluid(Pr=909) is investigated computationally under various operating conditions. The Reynolds number is varied from 0 to $5{\times}10^{-1}$, the Rayleigh number from $10^3$ to $5{\times}10^4$. The three-dimensional governing equations are discretized using the finite volume method. The effects of Reynolds number and Rayleigh number are presented and discussed. From a parametric study, it is found that vortex flow pattern of mixed convection in rectangular channels can be classified into three flow patterns basically, but the new vortex flow structures containing wave rolls are found, which are affected by Rayleigh number and Reynolds number. From this results, we can draw a flow regime map to delineate various vortex flow patterns in the high viscosity fluid mixed convective flow.