• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.9
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• pp.718-721
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• 2009

A new progressive advanced approach (Loop thermosyphon Thermoelectric Power generation System) is suggested to optimize heat recovery ability from vehicle exhaust gas. As an initial look at device feasibility, the present new TE system adopted the loop thermosyphon as a cooling heat exchanger. The TE system with loop thermosyphon was investigated in terms of working fluids, instability of system, amount of working fluid, and so on. Basically, the present experimental works have been focused on finding the optimum working condition of the system to improve thermoelectric power output and to obtain stable power generation to operate hybrid vehicles. The present experimental results with the loop thermosyphon TE module shows possibilities as an improved TE system for future thermoelectric hybrid vehicles.

• Journal of the Korean Solar Energy Society
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• v.22 no.2
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• pp.39-47
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• 2002

The thermosyphon SDHWS and the loop type thermosyphon systems are widely used for domestic hot water system. The loop type thermosyphon is a circulation device for transferring the heat produced at the evaporator to the condenser area in the loop. In this study, the operating characteristics of various working fluids being used have been identified. The working fluids employed in the study were ethanol. water, and a binary mixture of ethanol and water. The volume of working fluid used in this study were 30%, 40%, 50%, 60% and 70% of evaporator volume. It is observed that, in the thermosyphon with low volume of working fluid, such as 30% or 40%, the fluid was dried out. The flow pattern and mechanism of the heat transfer were identified through this study. Flow patterns of the binary mixture working fluid were also investigated, and the patterns were recorded in the camera. The system parameters were calculated using the thermal performance data. Modelling of the system was carried out using PSTAR method and TRNSYS program.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.271-278
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• 2020

The investigation into a full-scale 27 m high, by 6 m wide, thermosyphon loop. The simulation model is based on a one-dimensional axially-symmetrical control volume approach, where the loop is divided into a series of discreet control volumes. The three conservation equations, namely, mass, momentum and energy, were applied to these control volumes and solved with an explicit numerical method. The flow is assumed to be quasi-static, implying that the mass-flow rate changes over time. However, at any instant in time the mass-flow rate is constant around the loop. The boussinesq approximation was invoked, and a reasonable correlation between the experimental and theoretical results was obtained. Experimental results are presented and the flow regimes of the working fluid inside the loop identified. The results indicate that a series of such thermosyphon loops can be used as a cavity cooling system and that the one-dimensional theoretical model can predict the internal temperature and mass-flow rate of the thermosyphon loop.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.3
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• pp.153-161
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• 2002

Due to the coupling between momentum and energy transport theoretical analysis of the loop performance is very complicate, therefore it is necessary that these problems be solved by experimental investigation before applying the loop thermosyphon to heat exchanger de-sign. The evaporator and condenser of the loop thermosyphon were made of carbon-steel, and distilled water was used as working fluid in the experiments. From the experimental data correlations of heat transfer coefficient for evaporator and condenser sections were obtained. For heat fluxes in the range of 13000~78000 W/$m^2$, the correlation equations of heat transfer coefficients in evaporator and condenser predict the experimental behavior to within $\pm$5% and $\pm$20% respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.462-473
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• 2001

Due to the coupling between momentum and energy transport theoretical analysis of the loop performance is very complicate, therefore it is necessary that these problems be solved by experimental investigation before applying th loop thermosyphon to heat exchanger design. The evaporator and condenser of the loop thermosyphon were made of carbon-steel, and distilled water was used as working fluid in the experiments. From the experimental data correlations of heat transfer coefficient for evaporator and condenser sections were obtained. For heat fluxes in th range of 13~78kW/$m^2$, the correlation equations of heat transfer coefficients in evaporator and condenser predict the experimental behavior to within $\p$\pm$5% and\;\pm20$% respectively.

• 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 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.3 s.246
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• pp.246-254
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• 2006

The present study shows the experimental and modeling results of the cooling system using nanofludic loop thermosyphon. the experimental results show that nanofluid is not effective for small scale cooling system. The heat transfer performance is not much improved with the current small scale loop system comparing with the convectional water based loop system. In this study, various effects of nanofluids such as the concentration, the md of particle, host fluid, and heat capacity and so on were investigated. With nanofluid as the working fluid, the flow instability was improved at a certain concentration.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.725-728
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• 2002

A separate type thermosyphon can be utilized as a cooling device of electronic equipments (such as CPU of a personal computer or notebook). This study was carried out to investigate the cooling effect of separate type thermosyphon and to find the adequate parameters affecting the separate type thermosyphon. The heat transfer characteristics of separate type thermosyphon were obtained from experimental results. A $50{\times}50{\times}2 mm$ heat source was copied after CPU for the experiments. The results indicate that the device is capable of dissipating 60W of thermal energy and keeping the heat plate surface temperature under 50'E and the device can transfer heat from the evaporator to the condenser through natural circulation (without any external driving forces). Some transport phenomena of the working fluid and the heat transfer characteristics of the loop were observed in the experiments and are discussed in detail below.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.1019-1028
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• 2002

The instability of two-phase loop thermosyphons was investigated experimentally and analytically. Three orifice type inserts were used to study the effect of change in the pressure drop in the flow channel of the TLT on the flow instability and temperature fluctuation. It is observed that a decrease in the size of the orifice insert from 3.7 mm (no insert) to 0.71 mm drastically reduced the fluctuation of the temperature, especially at the evaporator section of the TLT. With the orifice type insert of 0.71 mm for the TLT, the overall temperature fluctuation was almost completely eliminated, especially at higher power input to the TLT The analysis based on the Kelvin-Helmholtz instability theory seems to predict reasonable well the loop stability state of the TLT with experimentally determined constant factors.