Effect of extreme wetting scenarios on pool boiling conditions

Teodori, Emanuele; Valente, T.; Malavasi, Ileana; Moita, Ana S.; Marengo, Marco; Moreira, A.L.N.

doi:10.1016/j.applthermaleng.2016.11.079

Cited by 64 publications

(21 citation statements)

References 35 publications

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“…The radial temperature profiles were obtained after post processing the IR images using a custom made, in-house developed MatLab code which allowed conversion of the raw IR images to temperature data. The high speed images were used to evaluate the spreading diameter i.e., the contact diameter and impact velocity using a code previously developed MatLab [40]. An example of the IR post processed images, temperature profiles as well as the raw and post-processed high speed images, is shown in Figure 3.…”

Section: Experimental Methodsmentioning

confidence: 99%

Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis

et al. 2017

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This study presents the numerical reproduction of the entire surface temperature field resulting from a water droplet spreading on a heated surface, which is compared with experimental data. High-speed infrared thermography of the back side of the surface and high-speed images of the side view of the impinging droplet were used to infer on the solid surface temperature field and on droplet dynamics. Numerical reproduction of the phenomena was performed using OpenFOAM CFD toolbox. An enhanced volume of fluid (VOF) model was further modified for this purpose. The proposed modifications include the coupling of temperature fields between the fluid and the solid regions, to account for transient heat conduction within the solid. The results evidence an extremely good agreement between the temporal evolution of the measured and simulated spreading factors of the considered droplet impacts. The numerical and experimental dimensionless surface temperature profiles within the solid surface and along the droplet radius, were also in good agreement. Most of the differences were within the experimental measurements uncertainty. The numerical results allowed relating the solid surface temperature profiles with the fluid flow. During spreading, liquid recirculation within the rim, leads to the appearance of different regions of heat transfer that can be correlated with the vorticity field within the droplet.

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Section: Experimental Methodsmentioning

confidence: 99%

Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis

et al. 2017

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“…In this state, droplets also have high static contact angles, but are strongly pinned in place due to high contact angle hysteresis [22,23]. In boiling, superhydrophobic surfaces have commonly been shown to transition to film boiling upon incipience, rendering them useless in application despite having favorable incipience superheats [29][30][31][32][33]. Recently, however, the authors have demonstrated the ability to limit vapor spreading during boiling on superhydrophobic surfaces by bringing these surfaces into the Wenzel state prior to boiling [34].…”

Section: Introductionmentioning

confidence: 99%

The petal effect of parahydrophobic surfaces offers low receding contact angles that promote effective boiling

Allred

Weibel

Garimella

2019

International Journal of Heat and Mass Transfer

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Despite extensive study of boiling processes and their widespread use in industry, critical interactions between the fluid and surface during boiling remain poorly understood. Simplistic, static descriptions of the contact angle are still relied upon to describe the effects of surface wettability on dynamic interfacial processes that govern boiling. This work demonstrates the critical role of the dynamic wettability characteristics of a surface on bubble growth dynamics and boiling performance. In spite of their superior nucleation behavior, hydrophobic surfaces have received little attention for boiling applications due to their typically premature transition from efficient nucleate boiling to inefficient film boiling. Evaluation of hydrophobic surfaces with high contact angle hysteresis reveals that the heat transfer efficacy of these surfaces can be exploited in boiling, so long as the receding contact angle of the surface is sufficiently small to mitigate vapor spreading and thereby extend the nucleate boiling regime. A new paradigm of textured boiling surfaces-parahydrophobic surfaces that exhibit the "petal effect" and mimic the wetting behavior of a rose petal-are shown to have untapped potential in boiling applications resulting from highly hydrophobic behavior coupled with low receding contact angles.

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“…Textured superhydrophilic surfaces have shown significant enhancement of CHF through capillary wicking, albeit with delayed incipience and moderately reduced heat transfer coefficients during boiling; they have been thoroughly investigated for high-heat-flux boiling applications [5,20,21]. Conversely, superhydrophobic surfaces have been observed to drastically reduce the critical heat flux, often immediately transitioning to film boiling at boiling incipience, with little or no nucleate boiling observed, as summarized in Table I [22][23][24][25][26]; despite any potential increase in the heat transfer coefficient, the narrow range of nucleate boiling operation has precluded consideration of superhydrophobic surfaces for practical boiling applications. In an attempt to utilize the favorable boiling characteristics of hydrophobicity, without the concomitant reduction in CHF, heterogeneous surfaces have recently been proposed that add hydrophobic regions to act as nucleation sites on hydrophilic surfaces [27,28]; in some cases, simultaneous improvement in the heat transfer coefficient and CHF has been observed compared to uniform hydrophilic surfaces [29][30][31].…”

mentioning

confidence: 99%

Enabling Highly Effective Boiling from Superhydrophobic Surfaces

2018

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A variety of industrial applications such as power generation, water distillation, and high-density cooling rely on heat transfer processes involving boiling. Enhancements to the boiling process can improve the energy efficiency and performance across multiple industries. Highly wetting textured surfaces have shown promise in boiling applications since capillary wicking increases the maximum heat flux that can be dissipated. Conversely, highly nonwetting textured (superhydrophobic) surfaces have been largely dismissed for these applications as they have been shown to promote formation of an insulating vapor film that greatly diminishes heat transfer efficiency. The current Letter shows that boiling from a superhydrophobic surface in an initial Wenzel state, in which the surface texture is infiltrated with liquid, results in remarkably low surface superheat with nucleate boiling sustained up to a critical heat flux typical of hydrophilic wetting surfaces, and thus upends this conventional wisdom. Two distinct boiling behaviors are demonstrated on both micro- and nanostructured superhydrophobic surfaces based on the initial wetting state. For an initial surface condition in which vapor occupies the interstices of the surface texture (Cassie-Baxter state), premature film boiling occurs, as has been commonly observed in the literature. However, if the surface texture is infiltrated with liquid (Wenzel state) prior to boiling, drastically improved thermal performance is observed; in this wetting state, the three-phase contact line is pinned during vapor bubble growth, which prevents the development of a vapor film over the surface and maintains efficient nucleate boiling behavior.

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Effect of extreme wetting scenarios on pool boiling conditions

Cited by 64 publications

References 35 publications

Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis

Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis

The petal effect of parahydrophobic surfaces offers low receding contact angles that promote effective boiling

Enabling Highly Effective Boiling from Superhydrophobic Surfaces

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