• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1102-1111
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• 2002

The study focuses on the heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having 50, 60, 70, 80, 90 internal grooves. Three different working fluids(distilled water, methanol, ethanol) are used with various volumetric liquid fill charge ratio from 10 to 40%. Additional experimental parameters such as operating temperature and inclination angle of zero to 90 degrees are used for the comparison of heat transfer performance of the thermosyphon. Condensation and boiling heat transfer coefficients, heat flux are obtained using experimental data for each case of specific parameter. The experimental results are assessed and compared with existing correlations. The results show that working fluids, liquid fill charge ratio, number of grooves and inclination angle are very important factors for the operation of thermosyphons. The relatively high rate of heat transfer is achieved when the thermosyphon with internal grooves is used compared to that with plain tube. The optimum liquid fill charge ratio for the best heat transfer performance lies between 25% and 30%. The range of the optimum inclination angle for this study is 20$^{\circ}$～30$^{\circ}$ from the horizontal position.

• 설비공학논문집
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• 제16권8호
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• pp.741-747
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• 2004

The purpose of this study was to develop a cooler/heater using a thermoelectric module combined with a parallel flow type oscillating heat pipe with R-142b as a work ing fluid. The experiment was performed for 16 thermoelectric modules (6 A/15 V, size: 40${\times}$40${\times}$4 mm), varying design parameters of the heat pipe (inclination angle, working fluid charging ratio, etc) . Experimental results indicate that the optimum charging ratio and the inclination angle of the parallel flow type oscillating heat pipe were 30% by volume and 30%, respectively. The maximum cooler/heater capacity were 479W (COP : 0.47) and 630W (COP : 0.9), respectively.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.353-356
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• 2008

일정 압력으로 혼합하는 이젝터에서 수축률(Contraction Ratio)로 대변되는 초음속 이젝터 설계 인자에 대한 연구가 수행되었다. 이젝터 설계 인자는 1차 유동과 2차 유동의 질량 유량 비율, 1차 유동면적과 2차 유동 면적의 비율, 1차 유동의 마하수에 영향을 받는 다는 것을 알 수 있었다. 그리고 특정 작동 조건에 대해 이젝터 유동 가시화 작업을 수행하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.572-578
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• 2001

This study is to research the heat transfer characteristics in copper-water heat pipes with screen wick, #100. Recently, the semiconductor capacity of an electronic unit has been larger, on the contrary, its size is smaller than before. As a result, a high-performance cooling system is needed. Experimental variables are inclination angle and temperature of cooling water. The distilled water was used for the working fluid. At a inclination angle ${-6}^{\circ}$, #100 2layer screen mesh is shown the best heat transfer performance.

• 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.

• 설비공학논문집
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• 제23권3호
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• pp.223-230
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• 2011

The power cycle using ammonia-water mixture as a working fluid is a possible way to improve efficiency of the system of low-temperature source. In this work thermodynamic performance of the ammonia-water regenerative Rankine cycle with partial-boiling flow is analyzed for purpose of extracting maximum power from the source. Effects of the system parameters such as mass fraction of ammonia, turbine inlet pressure or ratio of partial-boiling flow on the system are parametrically investigated. Results show that the power output increases with the mass fraction of ammonia but has a maximum value with respect to the turbine inlet pressure, and is able to reach 22 kW per unit mass flow rate of source air at $180^{\circ}C$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권6호
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• pp.360-366
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• 2000

This paper presents the fabrication and test of a micropump consisting of a pair of Al flap valves and a phase-change type actuator. The actuator is composed of a heater, a silicone rubber diaphragm and a working fluid chamber. The diaphragm is actuated by the vaporization and the condensation of the working fluid. The micropump is fabricated by the anisotropic etching, the boron diffusion and the metal evaporation. The forward and the backward flow characteristics of the flap valves illustrate the appropriateness as a check valve. Also, the flow rate of the micropump is measured. When the square wave input voltage of 8 V, 70% duty ratio and 2 Hz is applied to the heater, the maximum flow rate of the micropump is $97\muell/min$ for zero pressure difference.

• 수산해양교육연구
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• 제16권2호
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• pp.257-270
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• 2004

The two-phase closed thermosyphon is a heat transfer device capable of transfer large quantities of heat from a source to a sink by taking advantage of the high heat transfer rates associated with the evaporation and condensation of a working fluid within the device. A study was carried out with the performance of the heat transfer of the thermosyphon having 50, 60, 70, 80, 90 internal micro grooves in which boiling and condensation occur. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphon is also tested for comparison. Water, methanol and ethanol have been used as the working fluids. The liquid filling as the ratio of working fluid volume to total volume of thermosyphon, the inclination angle, micro grooves and operating temperature have been used as the experimental parameters. The heat flux and the boiling and the condensation heat transfer coefficient and overall heat transfer coefficient at the condenser and evaporator zone are estimated from the experimental results. The experimental results have been assessed and compared with existing correlations. Imura's and Kusuda's correlation for boiling showed in good agreement with experimental results within ${\pm}20$％ in plain thermosyphon. The maximum heat transfer rate was obtained when the liquid fill ratio was about 25%. The high heat transfer coefficient was found between 25o and 30o of inclination angle for water and between 20o and 25o for methanol and ethanol. The relatively high rates of heat transfer have been achieved in the thermosyphon with internal micro grooves. The micro grooved thermosyphon having 60 grooves shows the best heat transfer coefficient in both condensation and boiling. The maximum enhancement (i.e. the ratio of the heat transfer coefficients of the micro grooved thermosyphon to plain thermosyphon) is 2.5 for condensation and 2.3 for boiling.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.178-181
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• 2008

Cylindrical stainless-steel/sodium heat pipe for a high-temperature application was manufactured and tested for transient and steady-state operations. The container material was made of stainless-steel 316, and the working fluid was sodium. Stainless-steel 316 mesh screen was inserted as a capillary structure. The working fluid fill charge ratio was approximately 64 $\sim$ 181% based on the pore space of the wick. The outer diameter of the heat pipe was 12.7 mm and the total length was 250 mm. The evaporator part was 150 mm and the condenser 80 mm. The performance test of the heat pipe has been conducted in the furnace with up to 800 W. The variation of the average heat transfer coefficient was investigated as a function of heat flux and vapor temperature. As input thermal load increased, it was showed that difference of temperatures in evaporator and condenser decreased and that operating section and heat transfer characteristics at the heat pipe increased.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.109-113
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• 1999

Thermal mass flow meter (TMF) is used measuring the small mass flow rate of gases. Generally, flow rate measuring accuracy of TMF is $\pm2{\%}$ of full scale. TMF is manufactured for specified working pressure and specified working gas by customer. If it were applied for different working pressure and gases, flow rate measurement accuracy decreased dramatically. In this study, a TMF tested with three different gases and pressure range of 0.2 MPa to 1.0 MPa. Effect of specific heat cause to increase flow measurement error as much as ratio of specific heat compare with reference gas. Pressure change cause to increase flowrate measurement deviation about $-0.2{\%}$ as the working pressure decreased 0.1 MPa.