Microtube Surfaces for the Simultaneous Enhancement of Efficiency and Critical Heat Flux during Pool Boiling

Song, Youngsup; Gong, Shuai; Vaartstra, Geoffrey; Wang, Evelyn N.

doi:10.1021/acsami.1c00750

Cited by 42 publications

(31 citation statements)

References 41 publications

(64 reference statements)

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“…According to the theoretical analysis for active cavity sizes for nucleate boiling, [ 13 ] 5 and 12 µm cavities were chosen to initiate vapor nucleation at 11 and 5 °C wall superheats, respectively. [ 10 ] The cluster‐to‐cluster pitch was set to 2 mm based on the capillary length of water (≈2.5 mm) (Figure 1a), which has been found as an optimal distance between nucleation sites for effective separation of vapor bubbles in previous works. [ 10,14 ] On top of the microstructured surfaces, sharp blade‐like cupric oxide (CuO) nanostructures were created by sputtering a 500 nm copper layer over the microstructures followed by oxidation in an alkali solution (NaClO 2 , NaOH, Na 3 PO 4 , and deionized water with 3.75:5:10:100 wt%) at 95 °C for 2 min (SEM image in Figure 1c).…”

Section: Resultsmentioning

confidence: 99%

Three‐Tier Hierarchical Structures for Extreme Pool Boiling Heat Transfer Performance

et al. 2022

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The heat transfer coefficient (HTC, h) and critical heat flux (CHF, q″ CHF ) are two major parameters that quantify boiling performance. The HTC describes the efficiency of boiling heat transfer, defined as the ratio of heat flux (q″) to the wall superheat (ΔT w ), that is, h = q″/ΔT w . Here ΔT w is the temperature difference between the boiling surface and the saturated liquid. In the nucleate boiling regime, the heat flux increases with the wall superheat. However, when the heat flux is sufficiently high, excessive vapor bubbles nucleated on the boiling surface prevent the liquid from rewetting the surface and, in turn, form an insulating vapor film over the surface. This vapor film becomes a thermal barrier that leads to a drastic increase in wall superheat and burnout of a boiling system. This transition from nucleate boiling to film boiling is known as the boiling crisis, where the maximum heat flux is CHF. Enhancing CHF, therefore, can either enable larger safety margins or extend the operational heat flux range for boiling systems. [5] Recent efforts to enhance boiling heat transfer have focused on engineering the working fluid or surface properties. [6] In particular, engineering surface structures have received greater attention owing to the constraints on chemical compatibility or operational conditions which can limit the choice of the working fluid. Representative examples of surface structures that effectively enhance CHF are known to be hemi-wicking surfaces such as micropillars and nanowires. [7] These structures enhance CHF by harnessing thin-film evaporation around pillars and capillary-fed wicking through the structures. [8] Surfaces with microcavities, on the other hand, have shown improved HTC by trapping vapor embryos that promote nucleation. [9] Recently, a combination of microtube and micropillar structures referred to as tube-clusters in pillars (TIP), has shown the ability to tune the HTC and CHF by controlling bubble coalescence while maintaining capillary wicking. [10] Despite the controllability, achieving extreme enhancement of HTC and CHF simultaneously remains challenging due to the intrinsic tradeoff between HTC and CHF associated with nucleation-site density. For example, high nucleation-site density may increase HTC but decrease CHF because extensive bubble coalescence hinders the capillary wicking performance, while the reduced number of nucleation sites will limit the HTC enhancement.Boiling is an effective energy-transfer process with substantial utility in energy applications. Boiling performance is described mainly by the heat-transfer coefficient (HTC) and critical heat flux (CHF). Recent efforts for the simultaneous enhancement of HTC and CHF have been limited by an intrinsic trade-off between them-HTC enhancement requires high nucleation-site density, which can increase bubble coalescence resulting in limited CHF enhancement. In this work, this trade-off is overcome by designing three-tier hierarchical structures. The bubble coalescence is minimized to enhance the ...

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Section: Resultsmentioning

confidence: 99%

Three‐Tier Hierarchical Structures for Extreme Pool Boiling Heat Transfer Performance

et al. 2022

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“…Pool boiling is a widely used cooling technique in high heat flux applications such as integrated microelectronic devices, nuclear reactors, and space equipment. 1,2 To meet the increasing heat dissipation demands, various surface patterns have been designed and investigated to enhance pool boiling heat transfer, such as micro-pin-fin, 3 pillar, 4 micro/nano tube, 5,6 nanowire, 7 and microporous architecture. 8 Results indicate that surface wettability has significant influence on pool boiling because it affects bubble behaviors and liquid wetting state on the heating surface.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Pool boiling is a widely used cooling technique in high heat flux applications such as integrated microelectronic devices, nuclear reactors, and space equipment. , To meet the increasing heat dissipation demands, various surface patterns have been designed and investigated to enhance pool boiling heat transfer, such as micro-pin-fin, pillar, micro/nano tube, , nanowire, and microporous architecture . Results indicate that surface wettability has significant influence on pool boiling because it affects bubble behaviors and liquid wetting state on the heating surface. − Previous studies have reported that hydrophobic surfaces promote early onset of nucleate boiling (ONB), although bubbles tend to stay on hydrophobic surfaces, which leads to lower critical heat flux (CHF). On the contrary, hydrophilic surfaces delay the CHF, but they need larger superheat to initiate nucleate boiling. ,, …”

Section: Introductionmentioning

confidence: 99%

Influence of Surface Wettability on Bubble Formation and Motion

Xia

Gao

2021

Langmuir

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Bubble dynamics plays an important role in boiling heat transfer, and surface wettability affects bubble behaviors. In the present work, the effects of surface superhydrophilicity (SHI) and superhydrophobicity (SHO) on bubble dynamics are experimentally studied by observing the formation and motion behaviors of air bubbles and vapor bubbles on varied surfaces. For air bubbles to better mimic vapor bubbles, the air bubbles are introduced in a water pool by injecting airflow from a through hole of the surface. Air bubble tests are first conducted on homogeneous SHO and SHI surfaces, respectively. It is observed that surface wettability significantly affects the bubble size and departure frequency. To discover the dynamic behaviors of a bubble under both SHI and SHO, a biphilic surface with SHI and SHO areas is fabricated, and air bubbles are injected right on the biphilic border between the two areas. It is observed the wettability contrast significantly displaces the air bubbles, which spread only onto the SHO area. The biphilic surface is fabricated for the pool boiling test. Vapor bubbles are observed at different stages of the nucleate boiling, showing surface effects similar to the observations of air bubbles. Not only does this study present the influence of surface wettability on air and vapor bubble behaviors but also it provides useful implications for understanding and optimizing the biphilic surface design for enhancing boiling heat transfer.

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“…Furthermore, boiling heat transfer has already been utilized in the thermal management of high-power density system such as data centers, 4 high-power lighting equipment, 5 and especially for integrated electronics. 6 Flow boiling, making use of both the latent heat of phase-change and the forced convection, has been used for heat dissipation under extreme conditions such as for cooling of nuclear reactor fuel rods and for nuclear accident management. 7,8 Further enhancement of boiling heat transfer has become one of the important issues in both academic and industrial communities.…”

Section: Introductionmentioning

confidence: 99%

“…Phase-change heat transfer methods via boiling has become one of the most hopeful solutions owing to its ultra-high heat transfer efficiency. Furthermore, boiling heat transfer has already been utilized in the thermal management of high-power density system such as data centers, high-power lighting equipment, and especially for integrated electronics . Flow boiling, making use of both the latent heat of phase-change and the forced convection, has been used for heat dissipation under extreme conditions such as for cooling of nuclear reactor fuel rods and for nuclear accident management. , …”

Section: Introductionmentioning

confidence: 99%

Micro-pin-finned Surfaces with Fractal Treelike Hydrophilic Networks for Flow Boiling Enhancement

Yuan

Liu

Cui

et al. 2021

ACS Appl. Mater. Interfaces

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Due to its outstanding heat transfer performance, flow boiling has a wide range of applications in many fields, especially for cooling of electronic devices. Previous studies have shown that the liquid replenishment on the downstream of the heating surface is the critical restriction of the increase of the critical heat flux (CHF). In this work, we designed a series of heterogeneous surfaces with fractal treelike hydrophilic networks for flow boiling enhancement. The micro-pin-finned surface structures are expected to increase the CHF and reduce the superheat by its high wickability. Moreover, by virtue of the efficient transport capacity of treelike networks, the fractal hydrophilic paths are designed to serve as the liquid delivery channels for the liquid replenishment on the downstream of the heating surface. The heterogeneous surfaces improve the comprehensive boiling heat transfer performance, especially the CHF, which is 82.2% higher than that of the smooth surface and 5.4% higher than the surface homogeneously covered by the microstructure with twice of the extended surface area. This work provides reference for the design of heterogeneous surfaces with both smooth and structured parts to increase the flow boiling CHF to some extent.

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Microtube Surfaces for the Simultaneous Enhancement of Efficiency and Critical Heat Flux during Pool Boiling

Cited by 42 publications

References 41 publications

Three‐Tier Hierarchical Structures for Extreme Pool Boiling Heat Transfer Performance

Three‐Tier Hierarchical Structures for Extreme Pool Boiling Heat Transfer Performance

Influence of Surface Wettability on Bubble Formation and Motion

Micro-pin-finned Surfaces with Fractal Treelike Hydrophilic Networks for Flow Boiling Enhancement

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