• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.68-73
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• 2011

An experimental study was conducted to investigate the thermal performance of a medium-temperature heat pipe against the charge amount of working fluid. The container and the wick of the heat pipe were made of stainless steel and the working fluid was Dowtherm-A for medium-temperature applications around $250^{\circ}C$. The diameter and length of the heat pipe were 25.4 mm and 1 m, respectively. The maximum thermal load was 1 kW and the working fluid charge ratio varied from 372% to 420%. The results showed that the thermal resistance ranged from 0.12 to $250^{\circ}C/W$ and the effective thermal conductance ranged from 7,703 to $8,898 W/m{\cdot}K$. Dry-out occurred for the heat pipe with 372% fill-charge at the heat load of 950 W, while the other heat pipes with higher charge amount did not encounter dry-out up to 1060 W.

• 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.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1630-1637
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• 2002

A slab-wick heat pipe was fabricated and tested for applications where the condenser temperature is in a range of 80 to 12$0^{\circ}C$. The pipe material was 9.53 mm O.D. copper tube and the working fluids were ethanol and water. The total length of the heat pipe was 1.6 m, in which evaporator section was 1.4 m and the condenser was 0.10 m. The slab was a composite wick structure fabricated with STS316 wire screens. Thermal load was varied for a specified fill charge ratio and inclined angle. The optimum fill charge ratio was identified to be 110% based on a theoretical calculation of the pore space in the slab wick of the heat pipe. The maximum thermal load was 120W for ethanol and the same was 200W for water with the condenser temperature of 8$0^{\circ}C$. The thermal performance of the slab wick heat pipe is analysed in terms of temperature characteristics and thermal resistance against thermal load, tilt angle and fill charge ratio.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 추계학술대회 논문집(Proceeding of the KOSME 2000 Autumn Annual Meeting)
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• pp.43-49
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• 2000

Heat transfer characteristics of self oscillating heat pipe were experimentally investigated for the effect of fill charge ratios and heat loads. The heat pipe used for this study is made of copper capillary, has 0.002m internal diameter, a 0.34m length in one turn and consists of 19 turns. Heating and cooling section each have a length of 70mm. Water was used as working fluid inside heat pipe. As the experimental results, the self oscillating heat pipe was operated by self-exited oscillation and circulation of working fluid and the oscillation within the self oscillating heat pipe assumed chaotic behavior.

• 대한기계학회논문집B
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• 제24권3호
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• pp.346-353
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• 2000

In this paper, heat transfer characteristics of a loop type capillary heat pipe were experimentally investigated for the effect of several fill charge ratios of working fluid and heat loads. This type of heat pipe consists of a heating section, a cooling section and an adiabatic section. The heat pipe used has a 0.002m internal diameter, a 0.34m length in one turn and consists of 19 turns. Heating and cooling sections each have a length of 70mm. Experiments were performed to measure the temperature distributions and the pressure variation of the heat pipe. Heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients were calculated for various operating conditions of heat pipe and it was found that heat transfer characteristics of this type heat pipe were very excellent. As shown by this experimental study, this type of heat pipe operates by oscillatory flow caused by pressure and temperature oscillations.

• 설비공학논문집
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• 제11권3호
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• pp.313-320
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• 1999

A PFC(Perfluorocarbon) heat pipe has been used recently for cooling of GTO(gate turn off) thyristors or diodes in electric commuter trains. The present study was conducted to determine heat transport limitation of a PFC heat pipe which is one of the important parameters in heat pipes design. The variables such as tube diameter, fill charge ratio, internal surface structure and operating temperature were examined by way of experiment. Experimental data showed that the heat transport limitation of PFC heat pipe was considerably low and mostly dependent on tube diameter, with the value of 440~500W for d$o$/=22.23mm and 150~200W for d$o$=15.88mm. The other parameters had negligible effects, except for the case of small charge ratio less than 30%. Some correlations proposed by previous studies were in agreement with data from this study within 10~30%.

• 대한기계학회논문집B
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• 제22권9호
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• pp.1217-1228
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• 1998

In order to elucidate the operational characteristics of rotating heat pipes, the internal flow patterns and heat transfer performance are investigated. Flow patterns and its transition are studied with various rotational speeds by visualizing flows established inside a rotating tube. To verify those results of analysis, 2 heat pipes of the same geometries but fill charge rates of 7, 30% were manufactured and submitted to operating tests. Comparison of experimental results on heat transfer rate show a fairly good agreement with the analytical results. The analysis reveals that the optimum charge ratio is ranged in 4~7% depending on the quantity of thermal loads. but the heat pipe with 7% of fill charge ratio reached dry-out limitation at heat flux of $q^{{\prime}{\prime}}=6.2kW/m^2$ lower than that of analytic results. Transition of flow regime was well related to the correlation by Semena & Khmelev on transient centrifugal Froude Number Frc. But hysteresis phenomenon was observed in transition of flow regime, when the rotational speed was stepwisely changed in the way to undergo 1 cycle.

• 한국가스학회지
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• 제4권3호
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• pp.33-38
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• 2000

When fire and explosion accidents have occurred due to a leak of the flammable gas involving the LNG & LPG in an industrialized society, it is a very important problem. Accordingly, in this paper, we have compared and analyzed the occurrence transition and the electrostatic energy according to dust supplies and pressure variations for the electric charge due to the gas-solids of pipe flow. As the experimental results, if dust amounts and the initial pressure increased, electric charge in the pipe and the exit increased. The Specific charge of $Fe_2O_3$ increased proportionally if the initial pressure increased but if the quantity of dust increased, the specific charge decreased. Energy increased significantly as the dust amounts and the initial pressure increased. The possibility of fire and explosion exist in the measuring point(M 1) and the Faraday cage if natural gas and LPG were used.

• 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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• 제16권3호
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• pp.354-362
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• 2002

In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe.