Review on the fabrication of surface functional structures for enhancing heat transfer of heat pipes

Tang, Heng; Xie, Yansong; Xia, Liangfeng; Tang, Yong; Sun, Yalong

doi:10.1016/j.applthermaleng.2023.120337

Cited by 16 publications

(6 citation statements)

References 134 publications

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“…At a rotational speed of 1 rpm, the distribution bands of turbulent kinetic energy begin to break and then reco bine, gradually approaching the walls of the tank. This phenomenon is closely related previous studies on the formation of self-healing micelle structures by surfactants [21] (a) 1200 rpm (b) 1500 rpm…”

Section: Turbulent Kinetic Energysupporting

confidence: 91%

Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives

Chang,

Huang,

Wei

et al. 2024

Polymers

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In the practical application of hydraulic rotating machinery, it is essential to thoroughly explore drag reduction and rheological characteristics of drag-reducing additives to optimize machinery efficiency and reduce equipment consumption. This paper combines simulation and experimental approaches to investigate the drag-reduction performance and rheological properties of drag-reducing additives. Numerical simulations are initially conducted to investigate the shear-thinning properties of drag-reducing fluid and explore variations in drag-reduction rate. Turbulent phenomena characteristics are described by analyzing turbulent statistical quantities. Subsequently, the rheological behaviors of polyethylene oxide (PEO), cetyltrimethyl ammonium chloride (CTAC), and their mixed solutions under different conditions are scrutinized using a rotational rheometer. The findings indicate that the drag reduction effect amplifies as the rheological index n and characteristic time λ decrease. The numerical simulations show a maximum drag reduction rate of 20.18%. In rheological experiments, a three-stage viscosity variation is observed in single drag-reducing additives: shear thickening, shear thinning, and eventual stabilization. Composite drag-reducing additives significantly reduce the apparent viscosity at low shear rates, thereby strengthening the shear resistance of the system.

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Section: Turbulent Kinetic Energysupporting

confidence: 91%

Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives

Chang,

Huang,

Wei

et al. 2024

Polymers

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“…Hence, decreasing the local mass density can effectively increase the distance between the Na atoms, resulting in a continuous increase in PE, according to Equation (2). Note that the same behavior was also observed for Cases B3-900 (film boiling) and B3-800 (cluster boiling).…”

Section: Transition From Normal Evaporation To Cluster/film Boilingsupporting

confidence: 55%

“…The absorbed thermal energy is transformed into atomic kinetic energy, resulting in a considerable enhancement in the KE, which promotes the high excitation of Na atoms; hence, thermal expansion occurs in the liquid film, which makes the local mass density constantly and gradually decrease. Hence, decreasing the local mass density can effectively increase the distance between the Na atoms, resulting in a continuous increase in PE, according to Equation (2). Note that the same behavior was also observed for Cases B3-900 (film boiling) and B3-800 (cluster boiling).…”

Section: Transition From Normal Evaporation To Cluster/film Boilingsupporting

confidence: 55%

“…Among numerous methods to improve solid surface properties, introducing surface roughness is one of the most promising and can significantly enhance phase transition heat transfer in various thermal management devices. For example, studies [2,3] have revealed that the direct deposition of nanoparticles on the wick surface of wicked heat pipes (WHPs) could improve their thermal performance. Although macro-experimental studies have confirmed the effects of surface roughness on phase transition heat transfer, molecular dynamics (MD) simulation could be an effective technique to gain a deeper understanding of the impact of non-smooth surfaces.…”

Section: Introductionmentioning

confidence: 99%

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A Molecular Dynamics Perspective on the Impacts of Random Rough Surface, Film Thickness, and Substrate Temperature on the Adsorbed Film’s Liquid–Vapor Phase Transition Regime

Fallahzadeh,

Bozzoli,

Cattani

et al. 2024

Sci

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While recent studies have proven an unexpected liquid–vapor phase transition of adsorbed liquid films, a comprehensive description of the mechanisms of different types of phase change regimes over realistic representations of random rough surfaces is absent in the literature. The current comprehensive study investigates the effects of a gold random rough surface, liquid film thickness, and substrate temperature on the liquid–vapor phase change regime of an adsorbed sodium liquid film, considering the evaporator section of a wicked heat pipe (WHP) using a molecular dynamics (MD) simulation. At first, to generate a realistic random rough surface, a new and promising method is proposed that is entirely based on MD simulations. Then, to simulate the evaporator section of a WHP, a unique configuration for eliminating the vapor domain is developed. The simulation results reveal that three distinct regimes, namely, normal evaporation, cluster boiling, and film boiling, could be identified, which are presented on two-dimensional diagrams with the substrate temperature and liquid film thickness as coordinates for the ideally smooth and random rough surfaces. The results also manifest that even though using the random rough surface could lead to different phase transition regimes, the type of regime depends mainly on the substrate temperature and liquid film thickness. Furthermore, this study displays two different modes for normal evaporation. Also, it is shown that the impacts of the liquid film thickness and substrate temperature on the mode of normal evaporation are much more significant than the surface roughness.

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“…Micro-grooves, owing to their high permeability, low flow resistance, and cost-effectiveness, are one of the most commonly used wick structures [5,6]. Currently, the principal approaches to further enhance the capillary wicking capability of micro-grooves mainly involve the development of advanced manufacturing methods to form special surface morphologies [7][8][9] and the optimization of capillary structure design [10]. There are various methods for fabricating micro-grooved wick structures.…”

Section: Introductionmentioning

confidence: 99%

Gradient-Pattern Micro-Grooved Wicks Fabricated by the Ultraviolet Nanosecond Laser Method and Their Enhanced Capillary Performance

Huang,

Liao,

Fan

et al. 2024

Micromachines

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Capillary-gradient wicks can achieve fast or directional liquid transport, but they face fabrication challenges by traditional methods in terms of precise patterns. Laser processing is a potential solution due to its high pattern accuracy, but there are a few studies on laser-processed capillary-gradient wicks. In this paper, capillary step-gradient micro-grooved wicks (CSMWs) were fabricated by an ultraviolet nanosecond pulsed laser, and their capillary performance was studied experimentally. The CSMWs could be divided into three regions with a decreasing capillary radius. The equilibrium rising height of the CSMWs was enhanced by 124% compared to the non-gradient parallel wick. Different from the classical Lucas–Washburn model describing a uniform non-gradient wick, secondary capillary acceleration was observed in the negative gradient direction of the CSMWs. With the increase in laser power and the decrease in scanning speed, the capillary performance was promoted, and the optimal laser processing parameters were 4 W-10 mm/s. The laser-enhanced capillary performance was attributed to the improved hydrophilicity and reduced capillary radius, which resulted from the increased surface roughness, protrusion morphology, and deep-narrow V-shaped grooves induced by the high energy density of the laser. Our study demonstrates that ultraviolet pulsed laser processing is a highly efficient and low-cost method for fabricating high-performance capillary gradient wicks.

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Review on the fabrication of surface functional structures for enhancing heat transfer of heat pipes

Cited by 16 publications

References 134 publications

Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives

Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives

A Molecular Dynamics Perspective on the Impacts of Random Rough Surface, Film Thickness, and Substrate Temperature on the Adsorbed Film’s Liquid–Vapor Phase Transition Regime

Gradient-Pattern Micro-Grooved Wicks Fabricated by the Ultraviolet Nanosecond Laser Method and Their Enhanced Capillary Performance

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