• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.717-724
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• 2002

A heat exchanger (100,000 W) using two-phase loop thermosyphons (TLT) was developed as a waste heat recovery system. An experimental and simulation study was carried out on the heat transfer characteristics of TLT heat exchanger, and the results from the experiments were used to see the possibility which the TLT heat exchanger could be an alternate solution for waste heat recovery system. The experimental results showed the provisional results as a waste heat recovery system. Also computer simulation code can predict the TLT system about the effects of various variables for the operation. Computer simulation results based on the thermal resistance networks were compared with the experimental results. The study clearly shows that the computer simulation for the TLT heat exchanger can Predict the most cases of the affecting parameters involved, provided that correct empirical correlations are used.

• Solar Energy
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• v.18 no.4
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• pp.59-66
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• 1998

It was compared with experimental data to verify TRNSYS Model of the thermosyphon hot water system and the various simulations were conducted to optimize the component parameters of the system. To obtain consistent simulation results the system model, which could accurately describ the thermal storage tank temperature stratification and the friction head for mass flow rate, was used. The optimization of collector parameters(collector aspect ratio, riser numbers per header unit length), thermal storage tank parameters(ratio of tank length to tank diameter, heat exchanger type), system parameters(ratio of tank volume to collector area) was simulated by TRNSYS program. The simulation results indicate that the system performance is more effected by collector aspect ratio and the ratio of tank volume to collector area than the othor parameters.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.80.2-80.2
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• 2008

• Solar Energy
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• v.12 no.3
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• pp.37-46
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• 1992

An experimental study was carried out to investigate the performance of a latent heat storage system using paraffin wax as the phase change material. A thermosyphon was employed to transfer heat from the hot ethylene glycol flowing across the evaporator section of the thermosyphon into the wax. In order to increase the effective thermal conductivity of wax, layers of copper wire mesh were immersed in the wax. Experiments were run for volume ratios of 2%, 3%, and 4%, varying mass flow rate of ethylene glycol in each case. Some of the important results are as follows : (1) The wire mesh enhanced the conductive hea transfer and thus, helped even out the temperature distribution in the wax : (2) The increase of the number of layers of wire mesh increased the conduction. However, it also resulted in increasing the resistance to the convective motion of liquefied wax : and (3) There is an optimal number of layers of wire mesh, maximizing the performance of the storage system, which occurred at a volume ratio of $3{\sim}4%$ in the present study.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.899-905
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• 2014

This paper describes preliminary research conducted for developing a high-efficiency clean large cauldron using the liquid-vapor phase change heat transfer. To improve the isothermal environment of the cauldron, naphthalene and FC-40 were selected as the working fluids to operate well in the temperature range of $100-200^{\circ}C$ and used in experimental investigations of the heat transfer characteristics. A two-phase closed thermosyphon was designed and built to demonstrate the functionality of the working fluids. Startup, boiling, and condensation tests were performed, and the test results were used to examine the possibility of complementary effects of the startup and heat transfer characteristics of the two-phase closed thermosyphon using a mixture of naphthalene and FC-40.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.476-483
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• 2017

The decay heat that is produced by nuclear reactor spent fuel must be cooled in a spent fuel storage pool. A wickless heat pipe or a vertical two-phase closed thermosyphon (TPCT) is used to remove this decay heat. The objective of this research is to investigate the thermal performance of a prototype model for a large-scale vertical TPCT as a passive cooling system for a nuclear research reactor spent fuel storage pool. An experimental investigation and numerical simulation using RELAP5/MOD 3.2 were used to investigate the TPCT thermal performance. The effects of the initial pressure, filling ratio, and heat load were analyzed. Demineralized water was used as the TPCT working fluid. The cooled water was circulated in the water jacket as a cooling system. The experimental results show that the best thermal performance was obtained at a thermal resistance of $0.22^{\circ}C/W$, the lowest initial pressure, a filling ratio of 60%, and a high evaporator heat load. The simulation model that was experimentally validated showed a pattern and trend line similar to those of the experiment and can be used to predict the heat transfer phenomena of TPCT with varying inputs.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2007.10a
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• pp.505-506
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• 2007

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.3
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• pp.27-35
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• 2001

Heat transfer characteristics of a heat exchanged for low temperature waste heat recovery using oscillating capillary tube heat pipe (OCHP) were evaluated against the charging ratio variation of working fluid and various working fluids. R-l42b, R-22 and R-290 were used as working a 2.6mm in outside diameter, 1.44mm in inside diameter with 101m length and 140 turns. Charging ratio of working fluid was 40% and 50%. water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and 9~27 $4kg/m^2s$, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-142b and R-290 and it was proportional to Figure of Merit for thermosyphon. As a result, it was thought that R-22 was the most reasonable working fluid of waste heat recovery for low temperature waste heat recovery.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1475-1483
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• 2004

Loop thermosyphon(LTS) has many good characteristics such as low thermal resistance, no power consumption, noiseless operation and small size. To investigate the overall performance of LTS, we have performed various experiments varying three parameters: input power of the heater, working fluid(water, ethanol, FC3283) and filling ratio of the working fluid. At a combination of these parameters, temperature measurements are made at many locations of the LTS. The temperature difference between the evaporator and the condenser is used to obtain the thermal resistance. In addition, flow visualization using a high speed camera is carried out. The thermal resistance is not constant. It is lower at higher input power, which is one of the distinct merits of LTS. Flow instabilities are frequently observed when changing the working fluid, the input power and the filling ratio. The results show that the LTS can be readily put into practical use. Future practical application in electronic cooling is recommended.

• Journal of Mechanical Science and Technology
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• v.15 no.1
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• pp.98-107
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• 2001

Continuing efforts to achieve increased circuit performance in electronic package have resulted in higher power density at chip and module level. As a result, the thermal management of electronic package has been important in maintaining or improving the reliability of the component. An experimental investigation of thermosyphonic boiling in vertical tube and channel made by two parallel rectangular plates was carried out in this study for possible application of the direct immersion cooling. Fluorinert FC-72 as a working fluid was used in this experiment. Asymmetric heated channel of open periphery with gap size of 1, 2, 4 and 26mm and uniformly heated vertical tubes with diameter of 9, 15 and 20mm were boiled at saturated condition. The boiling curves from tested surfaces exhibited the boiling hysteresis. It was also found that the gap size is not a significant parameter for the thermosyphonic boiling heat transfer with this Fluorinert. Rather pool boiling characteristics appeared for larger gap size and tube diameter. The heat transfer coefficients measured were also compared with the calculation results by Chens correlation.