CFD simulation of dynamic heat transfer behaviors in super-long thermosyphons for shallow geothermal application

Wang, Xiaoyuan; Líu, Hao; Wang, Yinfeng; Zhu, Yuezhao

doi:10.1016/j.applthermaleng.2020.115295

Cited by 34 publications

(3 citation statements)

References 24 publications

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“…A smooth straight tube with a length of 2m, an outer diameter of 22mm and a thickness of 1.5mm is connected with corrugated pipe. The working fluid is selected as ammonia and the filling ratio is 37% (working fluid volume/corrugated pipe volume) [9]. The tested borehole with 60m depth and diameter of 100mm located at the Nanjing city.…”

Section: Experimental Set-up and Proceduresmentioning

confidence: 99%

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Experimental investigation on temperature response and heat transfer characteristics of super-long flexible heat pipe for geothermal utilization

Liu,

Wang,

Zhu

2021

Preprint

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Section: Experimental Set-up and Proceduresmentioning

confidence: 99%

“…In addition, thermosyphon for geothermal utilization have the feature of large aspect ratio and high liquid column due to the long structure. The hydrostatic pressure of high liquid column inhibits the boiling of working fluid at the bottom part of thermosyphon and has a negatively influence on the thermal performance [8,9].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on temperature response and heat transfer characteristics of super-long flexible heat pipe for geothermal utilization

Liu,

Wang,

Zhu

2021

Preprint

Self Cite

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“…Moreover, the dry area in the pipe increases with an increase in the length of the adiabatic section at any given vapor temperature. At present, studies have shown that when ultra-long gravity heat pipes operate, problems such as unstable operation due to the instability of two-phase flow and high static water pressure that restricts heat transfer may occur [21][22][23]. Nevertheless, the current research results on vapor-liquid flow and phase change mechanisms of ultra-long gravity heat pipes mainly rely on reasonable deduction based on temperature and pressure data, and further experimental verification is still required.…”

Section: Introductionmentioning

confidence: 99%

Two-Phase Flow Visualization and Heat Transfer Characteristics Analysis in Ultra-Long Gravity Heat Pipe

Chen

Cen

et al. 2023

Energies

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The ultra-long gravity heat pipe has a long heat transfer distance and narrow working fluid flow channel within its tube. Due to these unique design features, the vapor–liquid counter-flow and heat transfer characteristics of these heat pipes are more complex than those found in conventional-size heat pipes. This paper innovatively proposes the design of a segmented visualization window structure of an ultra-long gravity heat pipe, which successfully overcomes the challenge of visualizing the internal flow during operations. A visualization experimental platform, measuring 40 m in height with an inner diameter of 7 mm and the aspect ratio up to 5714, was built to investigate the evolving characteristics of two-phase flows with an increasing heat input and the impact of the phase change flow characteristics on the thermal performance of ultra-long gravity heat pipes. The results obtained can provide guidance for the development of the internal structure of ultra-long gravity heat pipes that are being applied in exploiting geothermal energy. The results show that, at low heat input (200 W, 250 W), there are separate flow paths between the condensate return and the steam, but the high hydrostatic pressure due to the height of the liquid injection results in the presence of an unsaturated working fluid with a higher temperature in the liquid pool area, which has a lower evaporation rate, limiting the heat transfer through the heat pipe. It is found that if increasing the heat input up to 300 W, the evaporative phase change in the heating section becomes intense and stable. At the same time, despite the intermittent formation of liquid columns in the adiabatic section due to the vapor–liquid rolls, which increases the resistance to the vapor–liquid counter-flow, the liquid columns are blocked for a short period of time, and the path of steam rises and the condensate return is smooth, which does not seriously affect the steam condensation and liquid return evaporation. At this point, the overall temperature of the heat pipe is evenly distributed along the tube and the heat transfer performance is optimal. When the heat input further increases (350 W, 400 W), a large amount of condensate is trapped in the upper part of the adiabatic section and the condensing section by long liquid plugs for a long time. At this point, the condensate flow back to the heating section is significantly reduced, and the steam is seriously prevented from entering the condensation section, resulting in a significant increase in the temperature gradient between the lower part of the evaporating section and the upper part of the adiabatic section and deterioration of the heat transfer performance.

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CFD Analysis on the Multiphase Flow of the Wickless Sodium Heat Pipe with Non-condensable Gas

Guo

et al. 2023

Springer Proceedings in Physics

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CFD simulation of dynamic heat transfer behaviors in super-long thermosyphons for shallow geothermal application

Cited by 34 publications

References 24 publications

Experimental investigation on temperature response and heat transfer characteristics of super-long flexible heat pipe for geothermal utilization

Experimental investigation on temperature response and heat transfer characteristics of super-long flexible heat pipe for geothermal utilization

Two-Phase Flow Visualization and Heat Transfer Characteristics Analysis in Ultra-Long Gravity Heat Pipe

CFD Analysis on the Multiphase Flow of the Wickless Sodium Heat Pipe with Non-condensable Gas

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