Ultra-efficient heat pipes enabled by nickel-graphene nanocomposite coatings: Concept and fundamentals

Wei, Chang; Huang, Guanghan; Luo, Kai; Wang, Pengtao; Li, Chen

doi:10.1016/j.carbon.2022.01.064

Cited by 7 publications

(15 citation statements)

References 41 publications

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“…As a result, the temperature distribution with the inclination angle of 90°b ecame smoother. Temperature fluctuations observed in the smooth heat pipe with DWC under low heat flux24 were not observed in all test cases presented in this work (Figure4), indicating the benefit of groove structures inside the proposed heat pipe.The Ni-Gr-CuO heat pipe demonstrated the least temperature difference between the evaporator and condenser section compared to the other two heat pipes. Obviously, by integrating the nanostructures, the surface temperature inside the evaporator section became more uniform and the surface temperature at 5 cm was smaller than the other point at 10 cm.…”

mentioning

confidence: 72%

“…The inner surface morphologies of proposed heat pipes and schematic diagram of heat pipe testing setup 24 . Optical and related scanning electron microscope images of (a) copper groove, (b) Ni‐Gr coated groove, (c) CuO nanostructure coated groove structure, respectively, (d)installation positions of the surface thermocouples, and (e) schematic plot of heat pipe testing rig.…”

Section: Resultsmentioning

confidence: 99%

“…Based on the most recent progress of sustainable DWC achieved on graphene surfaces, 23 inducing sustainable DWC into the heat pipes with promoted condensation efficiency becomes feasible. Our previous study shows an up to seven times higher enhancement of the effective thermal conductivity ( k eff ) by only inducing sustainable DWC in the thermosyphons 24 . However, smooth metal surfaces without any wicking structures can result in unprecedented instability of boiling under low heat flux, limiting the uniformity of the heat pipe temperature 24,25 .…”

Section: Introductionmentioning

confidence: 99%

“…The groove-wicking structures inside the heat pipe can effectively manage the temperature fluctuation caused by the unique DWC returning mechanism under low heating loads. 24 The intrinsic promotion via alternating the condensation mode from FWC into DWC could greatly benefit the heat pipe performance, even more, when coupled with advanced wicking structures in the evaporator section. Ultrahigh k eff of ~140 kW/(m•K), almost 5.17 times higher in high power working conditions than that of traditional groove heat pipe (#1), has been achieved by coordinately promoting both the condensation and evaporation efficiency in the #3 test sample.…”

Section: Introductionmentioning

confidence: 99%

“…It was obviously different compared to the trends described in the other two heat pipes.Flooding at the end of the evaporator with 150 W was shown to be well managed. The intrinsic promotion induced by DWC couldF I G U R E 2The inner surface morphologies of proposed heat pipes and schematic diagram of heat pipe testing setup 24. Optical and related scanning electron microscope images of (a) copper groove, (b) Ni-Gr coated groove, (c) CuO nanostructure coated groove structure, respectively, (d)installation positions of the surface thermocouples, and (e) schematic plot of heat pipe testing rig.…”

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confidence: 99%

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Sustainable dropwise condensation enabled ultraefficient heat pipes

Wei

Luo

Wang

et al. 2023

Droplet

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Heat pipes play a critical role in determining the operations, safety, and energy efficiency of electronics. The main focus to improve the heat pipe performance is on the evaporator design or wicking structures. However, the intrinsic limitation comes from the condenser, which is fundamentally constrained by inefficient filmwise condensation (FWC). In this study, we successfully achieved a peak effective thermal conductivity (k eff ) of ~140 kW/(m•K) on widely used groove heat pipes by implementing sustianble dropwise condensation (DWC) and integrating with enhanced evaporator. To better understand the working mechanisms of the ultraefficient heat pipe, both the evaporator and condenser of the heat pipes have been modified accordingly. Our results show that up to 296% enhancements on the k eff can be achieved under various inclination angles by only inducing DWC in the condenser section. The drawback of temperature fluctuations induced by DWC in smooth heat pipes appears to be effectively solved using the grooves-wicking structure. Furthermore, by integrating the nanostructured evaporator, the k eff of the heat pipe can be boosted up to 517% compared to conventional groove heat pipes.This study, for the first time, demonstrates the huge potential of engineering both the condenser and evaporator simultaneously in developing ultraefficient heat pipes.

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mentioning

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Sustainable dropwise condensation enabled ultraefficient heat pipes

Wei

Luo

Wang

et al. 2023

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Lightweight All Graphene‐Based Two‐Phase Heat Transport Devices

Zheng

Shen

Wang

et al. 2023

Adv Materials Inter

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interactions of weak van der Waals force to form thick graphene-based film, and the films are not strong enough to withstand tensile and compression due to weak connection. [1] Past efforts in solving this problem were focused on improving the strength of graphene-based films through incorporating a polymer as a binder. [2][3][4] While this strategy has helped improve the mechanical performance of graphene-based films, it leads to the deterioration of other properties, such as thermal properties. The use of polymer binders greatly reduces the thermal conductivity of graphene-based film due to the low thermal conductivity of polymers and the high inherent interfacial thermal resistance between graphene and polymers. [5,6] To improve the thermal conductivity of graphene-based films, one effective solution is to incorporate polymers with high intrinsic thermal conductivity, [7] but the improvement is limited to a certain level.In order to generate graphene-based systems with high thermal conductivity, graphene films can be used as casing materials to prepare a two-phase heat transport device (TPHTD). Such a device mainly relies on the phase change heat transfer process and takes advantage of both the large latent heat and the fast flow of the vapor from the evaporator to the condenser to realize efficient heat transfer, thus achieving high thermal conductivity, enabling its extensive use in thermal management devices. [8][9][10] So far, graphene has been used in two different ways for the TPHTD. In one way, graphene is coated on the inner wall of the metal-based casing in the TPHTD. [11][12][13][14] While this approach improves the thermal conductivity of the TPHTD due to good-wettability and low flow resistance of working medium on the surface of graphene, the resulting device is still heavy due to the metal-based casing, which does not take advantage of the lightweight property of graphene. The other is to use graphene as the casing material and metal frame as the support to prepare TPHTDs. [15] Such an approach still has not yet been realized to lightweight all graphene-based TPHTDs. To achieve all graphene-based TPHTDs with high thermal performance, an alternative approach is needed to form reliable binding between graphene nanosheets at nanoscale and achieve desired geometry of devices at macroscale. Graphene-based composites show great potential in the development of lightweight functional devices and systems, and polymers are usually used as binders to enhance the mechanical properties of these composites. Due to the low thermal conductivity of the polymer and the high inherent interfacial thermal resistance between polymer and graphene, however, the developed devices and systems generally possess low thermal conductivity, which seriously limits their further thermal-related applications. Here, a lightweight two-phase heat transport device (TPHTD) based on a vapor-liquid phase transition-based heat transfer by using a graphene-based composite material as the casing is generated. The graphene-based TPHTD has h...

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