• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.48-53
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• 2001

This experimental study is to research heat transfer characteristics in copper-water heat pipes with screen wick, the 150 and 200-mesh. Recent advances in the miniaturization and large capacity of electronic devices have had a major impact on the design of electronic equipment. As a result, a high-performance cooling system is needed. Experimental variables are inclination angle, number of layer and temperature of cooling water. The distilled water was used for the working fluid. At a inclination angle $6^{\circ}$, the 200-mesh screen wick 3-layer is shown the best heat transfer performance.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권1호
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• pp.1-9
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• 2004

The purpose of the present study is to examine the heat transport limitations in a screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6mm, and mesh numbers were 50, 100, 150, 200 and 250, and water was investigated as working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, the maximum heat transport limitations by capillary, entraintment, sonic and boiling were analyzed by a theoretical design method of heat pipe, including capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, etc. Based on the results, the capillary limitation in a small diameter of heat pipe is largely affected by mesh number and wick layer. Mesh number of 250 is desirable not to be used in pipe diameter of 6 mm, because capillary heat transport limitation decreases by the abrupt increase of liquid friction pressure due to the small liquid flow area. For the heat transport of 15 watt in 6mm diameter pipe, mesh number of 100 and one layer is an optimum wick condition, which thermal resistance is the smallest.

• 한국항공우주학회지
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• 제33권9호
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• pp.97-103
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• 2005

본 연구에서는 소형 동-소결윅 히트파이프를 대상으로 소결윅의 구조적 인자들이 히트파이프의 열수송 한계에 미치는 영향을 이론적으로 분석하였다. 소결윅의 입자 크기의 균일성과 소결 조건이 전체적인 기공분포와 기공률을 포함한 물리적 특성에 지배적인 요소로 작용했으며, 윅 두께 및 기공의 작은 편차가 히트파이프의 열수송 한계에 대체로 큰 영향을 미치는 것으로 나타났다. 특히, 증기온도와 경사각에 따라서 윅 두께와 평균 입자 반경, 그리고 모세관반경의 미세한 변화가 히트파이프의 모세관한계를 현저하게 변화시켰다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1400-1405
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• 2004

Experimental study is performed to investigate the effect of heat load and operating temperature on the thermal performance of a heat pipe with screen mesh wick. The heat pipe was designed in 200 screen meshes, 500mm length and 12.7mm O.D tube of copper, water as working fluid(4.8g) and nitrogen as non-condensible gas(NCG). The heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Experimental data of axial wall temperature distribution is presented for heat transport capacity, the temperature of cooling water of condenser, inclination angle, and operating temperature. For the results from this study, it is found that, for the same charging mass of working fluid, the initial operating temperature and the overall wall temperatures of heat pipe are higher for NCG charging mass of $5.0{\times}10^{-6}kg$ and $3.4{\times}10^{-6}kg$, than that of $1.0{\times}10^{-6}kg$.

• 설비공학논문집
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• 제20권10호
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• pp.689-695
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• 2008

Experimental study has been performed to investigate the influence of non-condensible gas(NCG) charged mass on the thermal performance of a variable conductance heat pipe(VCHP) with screen mesh wick. The VCHP is furnished by screen mesh number 200 for the pipe outer diameter of 12.7mm and the pipe length of 500 mm. The VCHP is filled with water as working fluid of 4.8g and nitrogen as NCG and has evaporator, condenser and adiabatic section, respectively. For the results from experiment, it is found that, for the same charged mass of working fluid, the overall wall temperatures of heat pipe grows up with increasing NCG charged mass. The variation of operating temperature of VCHP reduces with increasing NCG mass. In addition, the profile of axial wall temperature distribution is presented for heat transport capacity of heat pipe, the temperature of cooling water of condenser, inclination angle, and operating temperature.

• 한국유체기계학회 논문집
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• 제5권1호
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• pp.7-12
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• 2002

As the first step to investigate the fundamental mechanism of a dispersed two-phase flow, we studied the detailed interactions between bubble or particle motion and flow around it. Experiments were carried out with a rising bubble or particle in stagnant water in a vertical pipe. Particles with different densities, and/or different shapes were used for comparison with a bubble. We adopted 3D-PTV (Three-Dimensional Particle Tracking Velocimetry) for measuring the bubble or particle motions, and PIV (Particle Image Velocimetry) for measuring the water flow simultaneously (Hybrid PIV). The experimental results showed that the oblate spheroidal solid particle rose along the longer axis direction at the point that the inclination of the longer axis reached the maximum, and the inclination direction changed after moving. The bubble moved to the direction that the spheroid's projected width grew up to the largest, and the minor axis of the oblate spheroidal body of the bubble was parallel to the moving direction. The trajectory of the center of the particle/bubble which was measured with 3D-PTV, was marked on the section (x-y) of the pipe. It exhibited the pattern of the particle/bubble motion.

• 설비공학논문집
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• 제12권3호
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• pp.227-234
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• 2000

An experimental study was performed for understanding the limiting power and heat transfer characteristics of an MHP having the diameter of 3 or 4 mm which could be applied to cooling of miniature electronic equipment such as the notebook PC CPU etc. The experimental parameters which are inclination, structure of the wick, the length of the condenser and the total heat pipe were considered. The MHP with a woven-wired wick has the advantages of the improvement in capillary limit, the effective attachment tightly toward wall and the convenience in construction of wick. Cooling performance of the present MHP was compared with that of MHP with grooved, fine fiber and sintered type wick which were applied by existing enterprises. With respect to the inclination of$ -5^{\circ}$ , an MHP having the diameter of 3 or 4 mm shows the limiting power of 6~14 W. Therefore, it is expected that the MHP of the present study has sufficient applicability of cooling of notebook PC of which the amount of heat generated is about 12 W.

• 한국지반공학회논문집
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• 제20권8호
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• pp.59-66
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• 2004

본 연구에서는 연직말뚝과 경사말뚝에 대하여 모형실험과 수치해석을 실시하여 경사말뚝의 거동 특성을 분석하였다. 상대밀도 79%인 모래지반에 경사각도 0$^{\circ}$, $10^{\circ}$, 20$^{\circ}$, 30$^{\circ}$의 강관말뚝을 항타 관입하여 하중재하실험을 실시하였고, 상용 유한요소 프로그램인 PENTAGON 3D를 이용하여 수치해석을 수행하였다. 모형실험에 의한 경사말뚝의 축방향 지지 력은 경사각도가 $10^{\circ}$, 20$^{\circ}$, 30$^{\circ}$에서 연직말뚝에 비하여 111, 95, 81%로 나타났고, 수치해석의 결과도 다소 차이는 있지만 비슷하게 나타났다. 그러나 Petrasovits & Award의 결과는 경사각 $10^{\circ}$에서 모형실험 결과와 유사하지만, 경사각 20$^{\circ}$와 30$^{\circ}$에서는 모형실험결과를 과대평가하였다. 경사각도에 따른 주면마찰력과 선단하중은 모형실험과 수치해석 모두 $10^{\circ}$경사에서 최대값을 나타낸 후, 경사각도가 증가함에 따라 감소하였고, 전체하중에서 주면마찰력과 선단하중의 구성비율은 경사각도에 관계없이 거의 비슷하게 나타났다.

• 설비공학논문집
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• 제18권4호
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• pp.320-327
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• 2006

Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 mm length and 12.7 mm outer diameter tube of copper, water (4.8 g) is used as working fluid and nitrogen as non-condensible gas (NCG). Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Analysis values and experimental data of wall temperature distribution along axial length are presented for heat transport capacity, condenser cooling water temperature change, degrees of an inclination angle and operating temperature. These analysis and experiment give the follow findings: For the same charging mass of working fluid, the operating temperature of heat pipe becomes to be high with the increasing of charging mass of NCG. When the heat flux at the evaporator section increases, the vapor pressure in the pipe rises and consequently compresses the NCG to the condenser end part and increases the active length of the condenser. From previous process, it is found out we can control the operating temperature effectively and also the analysis and experimental results are relatively coincided well.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.460-465
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• 2003

Microgravity experiments were conducted to determine the effect of liquid and gas superficial velocities on flow behaviors. Flow behaviors observed under microgravity conditions can be classified into five flow patterns: bubble. Taylor bubble, slug, semi-annular and annular flows. Transition boundary between four flow patterns could be determined by drift-flux model. It was also found that the effect of gravity and pipe inclination on flow pattern transition was not significant in the inertia dominant region.