Morphed inception of dynamic Leidenfrost regime in colloidal dispersion droplets

Prasad, Gudlavalleti V V S Vara; Yadav, Mohit; Dhar, Purbarun; Samanta, Devranjan

doi:10.1063/5.0131609

Cited by 5 publications

(2 citation statements)

References 39 publications

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“…In comparison, no such nanoparticle deposition was noted for HPL nanofluid droplets at concentrations below 59.0 wt %, as evident in Figure a and c. Consequently, more pronounced nanoparticle deposition observed for HPO nanofluid droplets is likely one of the primary reasons for the elevated T L compared to the HPL nanofluid droplets. This increase in T L due to nanoparticle deposition is also reported by Paul et al and Prasda et al, who suggest that these deposited nanoparticles on the surface further increase the surface roughness and promote atomization by interrupting the pressure in the vapor film.…”

Section: Resultssupporting

confidence: 77%

“…Consequently, more pronounced nanoparticle deposition observed for HPO nanofluid droplets is likely one of the primary reasons for the elevated T L compared to the HPL nanofluid droplets. This increase in T L due to nanoparticle deposition is also reported by Paul et al 60 and Prasda et al, 61 who suggest that these deposited nanoparticles on the surface further increase the surface roughness and promote atomization by interrupting the pressure in the vapor film. A possible explanation for the different amounts of NP deposition between HPL and HPO nanofluid droplets is that, based on the thermodynamic energy argument, the HPO NPs are likely to be distributed on the droplet's surface, while the HPL NPs tend to distribute more uniformly throughout the bulk droplet since EG is a polar solvent.…”

Section: ■ Experimental Sectionsupporting

confidence: 77%

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Nanofluid Drop Impact on Heated Surfaces

Ma,

Aldhaleai,

Liu

et al. 2024

Langmuir

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We experimentally elucidate the impact dynamics of ethylene glycol (EG) droplets laden with both hydrophilic and hydrophobic SiO 2 nanoparticles (NPs) onto a flat heated surface in non-boiling, boiling, and Leidenfrost regimes. We use seven nanofluid concentrations (C p ), ranging from 0.89 to 64.3 wt %, and control the surface temperature (T s ) between 100 and 400 °C, while the nanofluid droplet's impact velocity is constant at 0.22 ± 0.02 m/s. Phase diagrams of impact outcomes are established to illustrate the effect of the additive nanoparticles on the droplets' impact dynamics, revealing that nanoparticles modify droplet impact behaviors differently in each regime. In the non-boiling regime, the droplet spreading profile remains unaffected by nanoparticles up to C p < 11.9 wt % before reaching the maximum spreading diameter (β max ). For nanofluid drops with higher nanofluid concentration, the increasing viscosity with concentration is likely to be the primary factor that affects the droplets' spreading profile in the non-boiling regime T s ≲ T sat ≈ 200 °C, as the saturation temperature. In the boiling regime 200 °C < T s ≲ 350 °C, a small amount of nanoparticle addition (C p = 0.89 wt %) promotes atomization regardless of nanoparticle wettability. Finally, manifested in a complete rebound due to an intervening vapor layer, the Leidenfrost temperature (T L ) of the nanofluid droplets is affected by both nanofluid concentration and nanoparticles' wettability. The nanofluid droplets' T L increases with higher nanofluid concentration; moreover, this Leidenfrost temperature increment is more significant for EG droplets laden with hydrophobic nanoparticles. Our results quantitatively reveal the significant influence of nanoparticle concentrations and wettability on drop spreading, impact outcome, and Leidenfrost temperature on heat surfaces, potentially benefiting applications in coating, spraying, and cooling.

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Section: Resultssupporting

confidence: 77%

Section: ■ Experimental Sectionsupporting

confidence: 77%

Nanofluid Drop Impact on Heated Surfaces

Ma,

Aldhaleai,

Liu

et al. 2024

Langmuir

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Leidenfrost limit enhancement via supersonically sprayed iron carboxylate framework for convection cooling

et al. 2023

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Device cooling schemes are required to reduce the local temperature of solar panels and solar air heaters, while maintaining their radiative heat to maximize energy conversion. Therefore, an efficient cooling scheme was developed using textured surfaces augmented by highly porous materials for increasing their total surface area. In this study, highly porous iron carboxylate framework, MIL-100(Fe), Materials of Institute Lavoisier, was introduced to substrates to provide a highly textured surface. This significantly reduced the temperature of the surface that was subject to radiative heat during both air and mist (or aerosol) cooling. In the case of mist cooling, the proposed MIL-100(Fe)-coated substrates were superhydrophilic, which promoted close contact between the impacting aerosols and the heated surface. Single drop impact and evaporation experiments were conducted to quantify the rate of heat removal provided by the proposed MIL-100(Fe) coatings. These coatings provided an increase in the Leidenfrost limit from 140 to 200 {degree sign}C. As such, the highly wettable and porous MIL-100(Fe)-coated layers promoted rapid evaporative cooling. The proposed layers were analyzed using scanning electron microscopy, X-ray diffraction, atomic force microscopy, and Brunauer-Emmett-Teller (BET) data to elucidate the reason for their increased heat transfer rate.

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Thermo-fluid-dynamics of inverse Leidenfrost levitation of small liquid/solid spheres over liquid pools

2023

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The present study provides a detailed theoretical investigation of the thermo-fluid-dynamics of the inverse Leidenfrost levitation phenomenon of a microscale droplet/solid on a liquid pool, and also the conditions essential for solid/liquid spherical objects to levitate. The theoretical model is developed for the floating characteristic of liquid/solid objects based on the thermo-fluid-dynamics of the vapor film during the inverse Leidenfrost effect. A very small thickness of the vapor layer, approximately of the order of micrometers, formed between the object and liquid pool during levitation, and its variation with the angular position and time history is considered in contrast to previous works. The actual magnitude of the overlapping contact angle is estimated and also incorporated in the present study. The effects of various influencing parameters, like nondimensionalized sphere radius, contact angle, and density ratio, on the levitation possibility and dynamics, are analyzed. The model is validated against experimental observations of the inverse Leidenfrost phenomenon for water drop levitating on a nitrogen liquid pool, and the effects of droplet parameters on total levitation time and dynamics are noted to provide accurate predictions. The approach presented is noted to provide a more accurate estimate of inverse Leidenfrost levitation compared to previous reports.

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Morphed inception of dynamic Leidenfrost regime in colloidal dispersion droplets

Cited by 5 publications

References 39 publications

Nanofluid Drop Impact on Heated Surfaces

Nanofluid Drop Impact on Heated Surfaces

Leidenfrost limit enhancement via supersonically sprayed iron carboxylate framework for convection cooling

Thermo-fluid-dynamics of inverse Leidenfrost levitation of small liquid/solid spheres over liquid pools

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