• Journal of Advanced Marine Engineering and Technology
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• 제30권6호
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• pp.702-708
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• 2006

This study shows the experimental characteristics of the double pipe inserted liquid pipe with small diameter in the gas pipe with large diameter for circulating of a liquid of high temperature, pressure and a gas of low temperature, pressure at the same time. So the functions of pipe and pipe's expansion and heat transfer are presented simultaneously. In the result, the temperature of gas refrigerant at the inlet of compressor increased about $5^{\circ}C$ by the heat transfer with liquid refrigerant in case of the double pipe. And liquid gas refrigerant which the temperature at the inlet of evaporator decreased about $3^{\circ}C$ comparing with the existing type flows into an evaporator COP of the double pipe increased about $7{\sim}10%$ comparing with that of the conventional pipe. And the noise of the double pipe at capillary tube is less than that of the conventional type about 3dB. Consequently. it is convinced the superiority of the double pipe in the heat loss and soundproofing aspect.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1058-1062
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• 2004

High-temperature cylindrical stainless steel/sodium heat pipe was manufactured and tested under long-term operation. The container material was stainless steel 316L and the working fluid was sodium. The heat pipe was 25.4 mm in diameter and 1000 mm in length with a two-layer screen mesh wick. The evaporator part was 600 mm and the condenser part was 300 mm in length. Total measurement points on heat pipe were 15 points and 12 points were located in condenser part. The heat pipe was heated for 142 days(3400 hours) at $800^{\circ}C$. In the test period, the maximum temperature difference was increased from $18^{\circ}C$ o $28^{\circ}C$ and the maximum thermal resistance was as low as $0.015^{\circ}CW$.

• 한국응용과학기술학회지
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• 제26권4호
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• pp.434-439
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• 2009

This paper is a new method for prevent. The particulate scale. stero-microscope were used for the scale removal experiment to improve mineralogical characteristics and the reduction of scales in heat pipe. Generally, the scale in the heat pipe consists of calcium carbonate minerals, such as calcite and aragonite which are precipitated by the reaction of Ca and $CO_2$ in the water. Copper alloy metal could eliminate the scale and prevent the production of scale in the heat pipe.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.103-106
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• 2002

This paper presents an effective numerical method for analyzing three-dimensional unsteady conjugate heat transfer problems of a curved pipe subjected to infernally thermal stratification. In the present numerical analyses, the thermally stratified flows in the pipe are simulated using the standard $k-{\varepsilon}$turbulent model and the unsteady conjugate heat transfer is treated numerically with a simple and convenient numerical technique. The unsteady conjugate heat transfer analysis method is implemented in a finite volume thermal-hydraulic computer code based on a non-staggered grid arrangement, SIMPLEC algorithm and higher-order bounded convection scheme. Numerical calculations have been performed far the two cases of thermally stratified pipe flows where the surging directions are opposite each other i.e. In-surge and out-surge. The results show that the present numerical analysis method is effective to solve the unsteady flow and conjugate heat transfer in a curved pipe subjected to infernally thermal stratification.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.741-745
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• 2001

The necessity of a Z-shape heat pipe may occur in a special application such as a cooling module for an electronic equipment having a limited accessible space. Either of the two end part works as evaporator or condenser and the length of the middle part is 200mm. The heat pipe was made of 3/8 inch copper tube having 60 spiral groove with screw angle of 10 degrees. Water and acetone were used as working fluids. The fill charge ratio of the working fluid was varied for different values of thermal loads. The thermal resistance was calculated based on the temperature measurements along the heat pipe axis. The maximum thermal loads were 80W for water and 100W for acetone heat pipe. The optimum fill charge ratio was identified through a series of experiments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.353-358
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• 2000

This paper presents the experimental investigation about miniature heat pipe for notebook PC. The focus of analysis is the operating temperature not to exceed $65^{\circ}C$ maximum allowable CPU surface temperature. Copper is used to heat pipe material and brass is wick material, and working fluid is selected to water. This cooling system is heat spreader method using a aluminum plate, since this method is most commonly used. According to the present study, heat for 3mm heat pipe, 8W, and for 4mm heat pipe, 10W, is found to power dissipation limit respectively, Soon after this investigation, sufficient long term life test should be followed.

• 설비공학논문집
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• 제8권1호
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• pp.13-25
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• 1996

The purpose of this paper is to study heat transfer characteristics of rotating heat pipe with tapered condensers by numerical analysis and experimental method. An experimental investigation has been carried out on thermal resistance between condenser wall and vapor region fo the rotating heat pipe with various taper 0, 1/11.4, 1/38. Heat transfer characteristics by analytical study were applied to describe various Nu numbers on the base of dimensionless condensate film, Re and Pr numbers in both condensers. Comparison between calculated results and experimental data showed qualitatively good agreement and the numerical analysis of this study can be utilized to predict the performance of a rotating heat pipe. The thermal resistance can be decreased by increasing the revolution per minute. Regardless of various dimensionless condensate film, Nu number was largely influenced by saturation temperatures of working fluid.

• 설비공학논문집
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• 제18권11호
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• pp.915-922
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• 2006

Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around $-20^{\circ}C$, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with $N_2$ gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around $-20^{\circ}C$. It was observed that the gas loaded one had succeeded in chilling start-up operation.

• 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.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1711-1727
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• 2001

Heat transfer coefficient were measured and new correlations were developed for two-phase heat transfer in a horizontal pipe for different patterns. Flow patterns were observed in a transparent circular pipe (2.54 cm I. D. and L/D=96) using an air/water mixture. Visual identification of the flow patterns was supplemented with photographic data and the results were plotted on the flow regime map proposed by Taitel and Dukler and agreed quite well with each other. A two-phase heat transfer experimental setup was built for this study and a total of 150 two-phase heat transfer data with different flow patterns were obtained under a uniform wall heat flux boundary condition. For these data, the superficial Reynolds number ranged from 640 to 35,500 for the liquid and from 540 to 21,200 for the gas. Our previously developed robust two-phase heat transfer correlation for a vertical pipe with modified constants predicted the horizontal pipe air-water heat transfer experimental data with good accuracy. Overall the proposed correlations predicted the data with a mean deviation of 1.0% and an rms deviation of 12%.