• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1533-1542
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• 2003

In the present study, the characteristics of pressure oscillation and heat transfer performance in an oscillating capillary tube heat pipe were experimentally investigated with respect to the heat flux, the charging ratio of working fluid, and the inclination angle to the horizontal orientation. The experimental results showed that the frequency of pressure oscillation was between 0.1 Hz and 1.5 Hz at the charging ratio of 40 vol.%. The saturation pressure of working fluid in the oscillating capillary tube heat pipe increased as the heat flux was increased. Also, as the charging ratio of working fluid was increased, the amplitude of pressure oscillation increased. When the pressure waves were symmetric sinusoidal waves at the charging ratios of 40 vol.% and 60 vol.%, the heat transfer performance was improved. At the charging ratios of 20 vol.% and 80 vol.%, the waveforms of pressure oscillation were more complicated, and the heat transfer performance reduced. At the charging ratio of 40. vol.%, the heat transfer performance of the OCHP was at the best when the inclination angle was 90$^{\circ}$ the pressure wave was a sinusoidal waveform, the pressure difference was at the least, the oscillation amplitude was at the least, and the frequency of pressure oscillation was the highest.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.309-314
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• 2008

increased heat dissipation and higher heat density of electronic equipment and/or parts released. A loop heat pipe(LHP) has been payed closer attention to the potential candidate of an electronic cooling. As of the LHP with a circular plate type evaporator developed, this study focused on its operating characteristics on the steady state in accordance with charging different working fluid. The relationship between working fluid and operating characteristics is discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.10
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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.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.214-222
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• 2001

The purpose of this research it to develop gas-air rotary heat exchanger using heat pipe and the performances were examined by way of the theoretical analysis and the experiment. Centrifugal force to return the working fluid in heat pipe elements with different radius was evaluated as a function of the revolution speed and inclination angle, and a rotary heat exchanger with 60 heat pipes in 3 rows was designed and manufactured. The inclination angle of a heat pipe relative to the revolving axis was designed to be 2$^{\circ}$and water was used as a working fluid. Experimental result showed the heat exchange rate was enhanced by 16% with compared to the calculated value.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.7-12
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• 2003

heat pipe with screen meshed wick. The heat pipe was designed in 200 screen meshs, 500 mm length and 12mm O.D tube of copper, water as working fluid and nitrogen as non-condensible gas. Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Experimental data of wall temperature distribution along axial length is presented for heat transport capacity, condensor cooling water temperature change, degrees of an inclination angle, and operating temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.1
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• pp.4-16
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• 1984

The heat-pipe is characterised by the highly effective thermal conductance. In order to change the thermal conductance, the heat-pipe is connected to a reservior having a space which is filled with non-condensable gas. In normal operation, the vapour of working fluid will tend to pump the non- condensable gas into the reservoir and the gas-vapour interface situates at some point along the condenser section. The thermal conductance is affected by non- condensable gas. It is concluded that the suitable position of interface can be used to control the temperature of condenser section. In this experiment, the evaporating part is connected to the lowest position of heat-pipe. The copper heat-pipe which is filled with Freon-113 or distilled water as working fluid utilized. As results of experimental study, thermal conductance can be increased by the operating pressure which is infulenced by non-condensable gas. A correlative equation between the thermal conductance and the mass of non- condensable gas is also obtained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.880-889
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• 2002

The purpose of the present study is to examine the factors affecting the heat transfer limitations of screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6 mm, and mesh numbers are 50, 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, capillary limitation, entrainment limitation, sonic limitation and boiling limitation we analyzed by theoretical design method of a heat pipe. As some results, the capillary limitation in small diameter of heat pipe is largely affected by mesh number and wick layer.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.1
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• pp.1-9
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• 2003

The examinations of the operating mechanism of an oscillating capillary tube heat pipe (OCHP) using the visualization method revealed that the working fluid in the OCHP oscillated to the axial direction by the contraction and expansion of vapor plugs. The contraction and expansion were due to the formation and extinction of bubbles in the evaporating and condensing part, respectively The actual physical mechanism, whereby the heat which was transferred in such an OCHP was complex and not well understood. In this study, a theoretical model of the OCHP was developed to model the oscillating motion of working fluid in the OCHP. The differential equations of two-phase flow were applied and simultaneous non-linear partial differential equations were solved. From the analysis of the numerical results, it was found that the oscillating motion Of working fluid in the OCHP was affected by the operation and design conditions such as the heat flux, the charging ratio of working fluid and the hydraulic diameter of flow channel. The simulation results showed that the proposed model and solution could be used for estimating the operating mechanism in the OCHP.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.3 no.2
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• pp.1-7
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• 2007

This paper is concerned with the selection of proper working fluids for medium temperature range heat pipe. The heat pipe which is made of SUS 316L has a total length of 700 mm as well as an outside diameter of 27.2 mm and a thickness of 2.1 mm respectively. Working fluids used in this study were Naphthalene, Biphenyl and Dowtherm A. Their charge amounts were about 40% of the inside volume of evaporator section. Experimental results shows that the Dowtherm A is good for $200^{\circ}C{\sim}300^{\circ}C$temperature range, while the Naphthalene is proper for $300^{\circ}C{\sim}430^{\circ}C$. In the case of the Naphthalene heat pipe, the heat transfer rate reaches 1500 W along with a vapor temperature of $430^{\circ}C$.