Flow visualization and heat transfer performance of annular thermosyphon heat pipe

Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol

doi:10.1016/j.applthermaleng.2017.07.116

Cited by 29 publications

(4 citation statements)

References 32 publications

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“…Larger possible heat transfer area can lead to increase in heat transport capacity [8,9,11]. Kim et al [16] reported the visualization study in the vertical upward annular thermosyphon. They tried to find the difference from conventional thermosyphon and reported the annular thermosyphon is dominated by wall shear viscosity force than the buoyance force.…”

Section: Introductionmentioning

confidence: 99%

Thermal and Flow Characteristics in a Concentric Annular Heat Pipe Heat Sink

et al. 2020

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A concentric annular heat pipe heat sink (AHPHS) was proposed and fabricated to investigate its thermal behavior. The present AHPHS consists of two concentric pipes of different diameters, which create vacuumed annular vapor space. The main advantage of the AHPHS as a heat sink is that it can largely increase the heat transfer area for cooling compared to conventional heat pipes. In the current AHPHS, condensation takes place along the whole annular space from the certain heating area as the evaporator section. Therefore, the whole inner space of the AHPHS except the heating area can be considered the condenser. In the present study, AHPHSs of different diameters were fabricated and studied experimentally. Basic studies were carried out with a 50 mm-long stainless steel AHPHS with diameter ratios of 1.1 and 1.3 and the same inner tube diameter of 76 mm. Several experimental parameters such as volume fractions of 10–70%, different air flow velocity, flow configurations, and 10–50 W heat inputs were investigated to find their effects on the thermal performance of an AHPHS. Experimental results show that a 10% filling ratio was found to be the optimum charged amount in terms of temperature profile with a low heater surface temperature and water as the working fluid. For the methanol, a 40% filling ratio shows better temperature behavior. Internal working behavior shows not only circular motion but also 3-D flow characteristics moving in axial and circular directions simultaneously.

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Section: Introductionmentioning

confidence: 99%

Thermal and Flow Characteristics in a Concentric Annular Heat Pipe Heat Sink

et al. 2020

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“…The numerical results were compared with the existing numerical data and showed good consistency in all cases. Kim et al 11 visualized the thermosyphon and concentric annular thermosyphon. The effects of working fluid filling rate and channel cross‐sectional area on heat transfer performance were studied, and the changes of working fluid flow state under different heat loads were observed.…”

Section: Introduction and Literature Reviewmentioning

confidence: 99%

Isothermal performance of a temperature comparison source using potassium concentric annular heat pipe

Zhang

Guo

et al. 2022

Intl J of Energy Research

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Summary In the field of measurement, high‐precision thermocouples need higher precision calibration equipment. However, the metal temperature equalizing block used in traditional thermocouple calibration equipment has poor temperature uniformity, and the structure of gas‐controlled heat pipe is complex and expensive, and the concentric annular heat pipes have high isothermal performance and simple structure, which can be used to improve the calibration equipment. In this study, a temperature comparison source based on potassium concentric annular heat pipe was fabricated to replace the metal temperature equalizing block, the temperature stability and temperature uniformity within 0 to 16 cm of the different metering wells at 400°C, 500°C, and 600°C were experimentally studied. The temperature stability was ±0.0026 K and the maximum axial temperature difference within 6 to 10 cm of the metering well was 0.027 K. On the vertical section of concentric annular heat pipe, due to the high specific heat of liquid working fluid, the temperature of the metering well near the bottom is higher.

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“…Therefore, it is necessary to improve the heat transfer capacity of the heat pipe. 11–14 The FPHP is suitable for the rapid cooling of electronic equipment in a small space, which has good thermal conductivity, simple structure, and good temperature uniformity. 15,16 Flat plate microchannel heat pipe (MCHP) has better performance because of its microchannel structure, and it is one of the most optimized heat pipes at present.…”

Section: Introductionmentioning

confidence: 99%

“…Kim et al. 13 studied the visualization of the thermosiphon heat pipe. The bubbly flow, slug flow, churn flow, and churn-annular flow were visualized in the thermosiphon, and slug flow occurred at low heat flux while bubbly flow did not appear in the annular thermosiphon.…”

Section: Introductionmentioning

confidence: 99%

A visualization study on flat plate heat pipe (FPHP)

Wan

Gao

Wang

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part A:

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With the aim to analyze the flow pattern and heat transfer characteristics of the working fluid in a flat plate heat pipe (FPHP) which was sealed by a transparent tempered glass plate, ethanol, acetone, and R141b were taken as the working medium, and visual experiments were performed at different heat flux when the inclination angle was 90°. The vapor-liquid distribution and the heat transfer characteristics of the FPHP were investigated at different liquid filling ratios. According to the experimental results and the recording of high-speed cameras, some important conclusions had been drawn as follows: (i) As the power increases, the vapor-liquid interface in the FPHP declines and the effects of dryout is significantly intnsified, leading to a sharp increase in temperature. The FPHP with a filling ratios of 25.7% owns better thermal performance than that with the filling ratios of 11.8% and 66% at different heating power; (ii) the bubble generation inside the FPHP became more intense with increasing heat flux, and various bubble movement patterns were found at different the liquid filling ratios; (iii) As the liquid film flowed downward, the thickness of the liquid film increased at first and then decreases. The condensation of steam was reduced due to the thickening of the liquid film on the wall. The liquid film became thinner when it was entrapped and evaporated in the downward flow.

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Flow visualization and heat transfer performance of annular thermosyphon heat pipe

Cited by 29 publications

References 32 publications

Thermal and Flow Characteristics in a Concentric Annular Heat Pipe Heat Sink

Thermal and Flow Characteristics in a Concentric Annular Heat Pipe Heat Sink

Isothermal performance of a temperature comparison source using potassium concentric annular heat pipe

A visualization study on flat plate heat pipe (FPHP)

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