Nanofluid pendant droplet evaporation: Experiments and modeling

Gerken, William J.; Thomas, Abhay V.; Koratkar, Nikhil; Oehlschlaeger, Matthew A.

doi:10.1016/j.ijheatmasstransfer.2014.03.031

Cited by 44 publications

(14 citation statements)

References 28 publications

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“…They found the 2 -law to hold for weight concentration up to 1% and 2 2 ⁄ < 0.75 and the value to decrease from ≈ 0.0063 mm 2 s ⁄ for pure liquid to an asymptotic value ≈ 0.0054 mm 2 s ⁄ for weight concentration ≥ 1.5%. The qualitative trend in found in [42] is thus in agreement with those found in [20], but unlike [20] it begins to decrease for concentration slightly greater than zero. These researchers performed a modeling analysis and suggested that the particle packing near the droplet surface is responsible for the decrease in .…”

Section: Effect Of Initial Particle Concentration ( )supporting

confidence: 83%

“…Gerken et al [42] studied the effect of initial particle concentration in the Al-ethanol nanofluid (particle size range of 40 -60 nm) droplet evaporation was investigated on its effect on the 2law. They found the 2 -law to hold for weight concentration up to 1% and 2 2 ⁄ < 0.75 and the value to decrease from ≈ 0.0063 mm 2 s ⁄ for pure liquid to an asymptotic value ≈ 0.0054 mm 2 s ⁄ for weight concentration ≥ 1.5%.…”

Section: Effect Of Initial Particle Concentration ( )mentioning

confidence: 99%

“…% nano-silica particles with an ambient temperature of 300K [16]. Because acoustic effects greatly enhance liquid circulation [16,42], making very small . The value of is enhanced by 1 million times, from the Einstein-Stokes diffusivity of 10 -12 m 2 /s to 10 -6 m 2 /s.…”

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confidence: 99%

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Effects of insoluble nano-particles on nanofluid droplet evaporation

Wei

Deng

Chen

2016

International Journal of Heat and Mass Transfer

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A model is presented for predicting the evaporation behavior of liquid droplets containing nanosized insoluble particles. The model is constructed based on, and supported by, the existing experimental result. Of particular interest are the evolution of droplet size, and evaporation rate constant prior to the shell formation (also called the first drying or evaporation stage), when the particles forms a compact shell at the droplet surface. As the droplet evaporation proceeds, increasingly more particles are "included" on its surface, reducing the effective liquid surface area for evaporation causing deviation from the classical 2-law for pure fluid droplet evaporation. Peclet number (Pe), a non-dimensional ratio of particle diffusion time to the droplet lifetime, and initial particle concentration (vo) are shown to play a role in the evaporation behavior prior to shell formation. The model predicts that: (1) the deviation from the classical 2-law is increasingly significant with increased Pe and vo ; (2) the time to shell formation decreases, and shell diameter increases, with increased Pe and initial particle concentration (vo). As a consequence, vo • < 1.8 is necessary for the first stage to exist at all. Within the limiting value, the combination of larger and smaller vo produces larger hollow shells with low densities. For vo • > 1.8 the shell forms instantly and evaporation occurs after liquid diffuses through, and wet, the shell. The effect of contact angle () on the effective liquid surface area for evaporation is also discussed.

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Section: Effect Of Initial Particle Concentration ( )supporting

confidence: 83%

Section: Effect Of Initial Particle Concentration ( )mentioning

confidence: 99%

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Effects of insoluble nano-particles on nanofluid droplet evaporation

Wei

Deng

Chen

2016

International Journal of Heat and Mass Transfer

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“…where 5 = liquid / gas (2) and is the radial distance from the droplet center, the droplet radius, ∞ is the velocity of the gas flow far away from the droplet, and are, respectively, the dynamic viscosities of fluids outside and inside the droplet, and is measured from the incoming flow, as shown in Fig. 1.…”

Section: Characteristic Times Of Particle Diffusion Internal Circulamentioning

confidence: 99%

“…Consequently, the nanofluid properties, namely Pe and initial particle concentration together plays an important role in affecting droplet evaporation rate even prior to shell formation, and thus affecting the deviation from the 2 -law [3][4][5], mainly arising from the inclusion process. (As a comparison, a multi-component droplets with soluble solids, the deviation from the 2 -law is attributed to variable liquid properties [6,7].)…”

Section: Introductionmentioning

confidence: 99%

Effects of internal circulation and particle mobility during nanofluid droplet evaporation

Wei

Deng

Chen

2016

International Journal of Heat and Mass Transfer

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The effect of internal circulation on evaporation of fluid droplets containing nano-sized particles is analytically investigated, where internal circulation is caused by viscous effects at the liquid-gas interface in the convective environment. The competing time scales of liquid diffusion, convection, and particle diffusion are first analyzed as influenced by gas phase velocity, relative viscosities of gas and liquid phases, and the droplet size. The results reveal the importance of internal recirculation for droplets of practical sizes. To demonstrate the role of internal circulation plays on particle distribution and shell formation during the evaporation process, a symmetric Hill vortex and strong circulation are assumed for solving a one-dimensional governing equation, which to yield (i) the particle redistribution during the evaporation process, (ii) the time and the size upon shell formation (i.e., the end of the first-stage evaporation/drying) due to inclusion of particles at the droplet surface, and (iii) internal particle distribution that forecast possible morphologies of particle aggregates once the drying process is complete. These results are found to be dependent upon (a) the relative time scales of liquid diffusion and particle mobility (the effect of Lewis number, ), and (b) the relative importance or evaporation rate ( ) and particle mobility (the effect of Peclet number, ). Comparisons with previous results without internal circulation are made, as related to the time for shell formation and possible morphologies. Such comparisons reveal some distinctly different, and surprising, phenomena during and at the end of the first-stage evaporation.

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