• Journal of Energy Engineering
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• v.23 no.2
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• pp.175-182
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• 2014

The use of solar energy among renewable energy tends to increase because of infinity and cleanness of resources. Even though the consumption rate of solar energy in our country is still low, however, in recent years, the research for solar energy have been widely conducted due to policy support of government. This study was performed to make the system of performance test for solar collector and to investigate thermal efficiency for solar collector with thermosyphon tube-type. As a result, in case of indoors measurement using halogen lamp, thermal efficiency for solar collector with thermosyphon tube-type was increased about 15~22% after 120 minutes compared with that of solar collector with double evacuated tube-type. In addition, in case of outdoors measurement, thermal efficiency of thermosyphon tube-type was showed maximum about 46% higher than double evacuated tube-type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.22-32
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• 1998

Separate type thermosyphon has larger critical heat flux than non-loop type thermosyphon, because the flooding phenomenon of vapor and liquid occurring in non-loop one does not occur. The experimental study has been carried out separate type thermosyphon with single tube. An investigation of heat transfer characteristics in separate type thermosyphon is performed experimentally. Heat transfer coefficients in an evaporator and condenser were measured experimentally. The effects of liquid filling ratio, height difference, cooling temperature and heat flux on the heat transfer coefficients were examined. As a result, the reasonable range of the liquid filling ratio and the dependence of heat transfer on vapor temperature and heat flux are obtained.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.356-361
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• 2012

Recently, even though the researches on renewable energy like geothermal, wind, solar energy have been performed widely, its use-rate in total energy is still low. This study was carried out to investigate the performance of hybrid heating system, which consisted of solar collector of thermosyphon tube type and X-L pipe boiler. Especially, new type of solar collector was tried and compared with double tube type and, futhermore, performance and safety on X-L pipe boiler were investigated. As the results, efficiency of solar collector of thermosyphon tube type was higher 20.7% than that of double tube type, mainly due to its structural characteristics. It was also confirmed that temperature of special heat medium used X-L pipe boiler rose up about 20% rapidly in comparison with that of pure water.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.3
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• pp.257-262
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• 2016

Flexible two-phase thermosyphons are devices that can transfer large amounts of heat flux with boiling and condensation of working fluid resulting from small temperature differences. A flexible two-phase thermosyphon consists of a evaporator, an insulation unit, and a condenser. The working fluid inside the evaporator is evaporated by heating the evaporator in the lower part of the flexible two-phase thermosyphon and the evaporated steam rises to the condenser in the upper part to transfer heat in response to the cooling fluid outside the tube. The resultant condensed working fluid flows downward along the inside surface of the tube due to gravity. These processes form a cycle. Using R134a refrigerant as the working fluid of a loop type flexible two-phase thermosyphon heat exchanger, an experiment was conducted to analyse changes in boiling heat transfer performances according to differences in the temperature of the oil for heating of the evaporator, the temperature variations of the refrigerant, and the mass flows. According to the results of the present study, the circulation rate of the refrigerant increased and the pressure in the evaporator also increased proportionally as the temperature of the oil in the evaporator increased. In addition, the heat transfer rate of the boiler increased as the temperature of the oil in the evaporator increased.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.239-244
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• 2003

This study concerns the performance of condensing heat transfer in two-phase closed thermosyphons with various helical grooves. Distilled water, methanol, ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The type of working fluid and the numbers of grooves of the thermosyphons with various helical grooves have been used as the experimental parameters. The experimental results have been assessed and compared with existing theories. The results show that the type of working fluids are very important factors for the operation of thermosyphons. And the maximum enhancement (i.e. the ratio of the heat transfer coefficients the helical thermosyphons to plain thermosyphons) is $1.5{\sim}2$ for condensation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.131-139
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• 2005

This study concerns the performance of boiling heat transfer in two-phase closed thermosyphons with various helical grooves. Distilled water, methanol, ethanol have been used as the working fluids. In the present work, a copper tube of the length of 1200 mm and 14.28 mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550 mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the Performances of having 50, 60, 70, 80 and 50 helical grooves. A Plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for comparison. The type of working fluid and the numbers of grooves of the thermosyphons with various helical grooves have been used as the experimental parameters. The experimental results have been assessed and compared with existing theories. The results show that the number of grooves and the type of working fluids are very important factors for the operation of thermosyphons. The helical grooved thermosyphons having 50 to 60 grooves in water, 60 to 70 grooves in methanol and ethanol shows the best heat boiling heat transfer coefficient.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.116-122
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• 2005

This study concerns the performance of condensing heat transfer in two-phase closed thermosyphons with various helical grooves. Distilled water, methanol, ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The type of working fluid and the numbers of grooves of the thermosyphons with various helical grooves have been used as the experimental parameters. The experimental results have been assessed and compared with existing theories. The results show that the type of working fluids are very important factors for the operation of thermosyphons. And the maximum enhancement (i.e. the ratio of the heat transfer coefficients the helical thermosyphons to plain thermosyphons) is $1.5{\sim}2$ for condensation.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.05a
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• pp.185-198
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• 1995

This is an experimental study conducted to visualize the nucleate boiling phenomena and flow regimes occurring inside the liquid pool in a closed two-phase thermosyphon. To meet this purpose, an annular-type thermosyphon was designed and manufactured using a glass tube and a stainless steel tube, being assembled axisymmetrically. The heat to be supplied to the working fluid is generated within a very thin layer of stainless steel tube wall by applying a high frequency electromagnetic field through the induction coil, axisymmetrically set around the evaporator zone. Some important results were as follows ; 1) Considering the structural complexity of the tested thermosyphon, it showed good performance for the range of heat flux 2＜ q" ＜25kW/$m^2$ and saturation vapor pressure, 0.1＜Pv＜1.1bar 2) different type of nucleating boiling regimes were observed as described below, -Pulse boiling regime : Flow pattern changed cyclically with time during 1 cycle of pulse boiling process. The onset of Nucleation was followed by expulsive growing of vapor bubble, resulting in the so called blow-up phenomenon, massive expulsion of large amount of liquid around the bubble. -Transient : Some spherical vapor bobbles were observed growing out from 2~3 nucleating sites, that was dispersed at the lower part of the heated tube wall in the liquid pool. But the rest upper region above the nucleating sites were filled with churns or bubbles of vapor. -Continuous nucleate boiling regime : The whole zone of evaporator was filled with lots of spherical vapor bubbles, and the bubbles showed tendency to decrease in diameter as the heat flux increased.ased.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1243-1249
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• 2004

This study is focused on the comparison between the internal saturation temperature of the working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves. Distilled water, methanol and ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The results show that the numbers of grooves and the type of working fluids are very important factors for the operation of thermosyphons. A good agreement between the internal saturation temperature of working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves is obtained.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.2
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• pp.305-311
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• 2003

This Paper Presents an information about the heat transfer characteristics of a separate type thermosyphon in electronic equipments. The heat removal problem of electronic equipments is regarded as an important factor and a separate type heatpipes can be utilized as a cooling device of electronic equipments (such as CPU of a Personal computer or notebook). In this study. heat source ($50\times50\times2 mm $aluminum Pseudo CPU) was used for the experiment. The device can transfer heat from the evaporator to the condenser through natural circulation (without any external driving forces) and the results indicate that the device is capable of dissipating over 60W of thermal energy and keeping the heating plate surface temperature under $50^{\circ}C$.