Key design and operating parameters for enhancing dropwise condensation through wettability patterning

Mahapatra, Pallab Sinha; Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine M.

doi:10.1016/j.ijheatmasstransfer.2015.08.106

Cited by 137 publications

(65 citation statements)

References 44 publications

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“…In recent years, renewed interest is given to the study of surface's wettability on condensation heat transfer [12][13][14]. Mixed wettability surfaces have been proposed to enhance condensation heat transfer [15][16][17][18][19][20]. Chatterjee et al [15] conducted an experiment to study condensation on surfaces with patterns of distinct hydrophilic and hydrophobic regions (island-patterns and tree-patterns), and observed better condensation heat transfer performance than those on uniform hydrophobic surfaces.…”

Section: Introductionmentioning

confidence: 99%

Lattice Boltzmann simulations for transition from dropwise to filmwise condensation on hydrophobic surfaces with hydrophilic spots

Cheng

2017

International Journal of Heat and Mass Transfer

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Transition from dropwise to filmwise condensation of a dry saturated vapor on downward-facing smooth subcooled horizontal hydrophobic walls with hydrophilic spots is simulated numerically using the newly developed phase-change lattice Boltzmann method. Dynamic behaviors including growth, coalescence and departure of condensate droplets from cooler surface are investigated. Effects of wall subcooling and wettability of the cooler surface on droplet departure diameter, average cycle time and nucleation time are presented. At small wall subcoolings, droplets are formed on hydrophilic spots of the hydrophobic surface. With increasing wall subcoolings, coalescence of droplets and their subsequent departure are observed. Further increase of the wall subcooling leads to transition from dropwise condensation to filmwise condensation mode, and droplets fall down from the subcooled surface at locations according to Taylor's unstable wavelength. The dropwise condensation curve in terms of average heat flux versus wall subcooling from droplet nucleation to peak dropwise condensation heat flux and its subsequent transition to filmwise condensation is obtained numerically for the first time. It is found that the location where droplet or liquid film in contact with the downwardfacing surface has a high local heat flux, especially around the triple-phase contact line. The degree of wall subcooling corresponding to peak dropwise condensation heat flux increases with the increasing pitch distance between hydrophilic spots. The cooler's hydrophobic surface with a smaller contact angle has a lower peak dropwise condensation heat flux which occurs at a smaller degree of wall subcooling. During transition from dropwise to filmwise condensation, there is a graduate reduction in wall heat flux under constant wall temperature conditions, and a sudden drop in the average wall temperature of the subcooled surface under constant wall heat flux conditions.

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Section: Introductionmentioning

confidence: 99%

Lattice Boltzmann simulations for transition from dropwise to filmwise condensation on hydrophobic surfaces with hydrophilic spots

Cheng

2017

International Journal of Heat and Mass Transfer

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“…The larger the angle of divergence, the faster the droplet moved, and the surface tension produced by the structure became higher than the gravity at a certain angle. Mahapatra et al [15] placed a superhydrophilic surface track in the center of a hydrophilic pattern and staggered parallel to the hydrophilic pattern. The heat transfer coefficient of the design at 29.9% filmwise area increased by 34.4% compared with that for completely dropwise condensation.…”

Section: Introductionmentioning

confidence: 99%

Visualization of Patterned Modified Surfaces in Condensation and Frosting States

Yang¹,

Lu²,

Wu³

2019

Energies

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In this study, a novel, thorn-shaped, containing, hydrophilic, and hydrophobic surface is proposed to have a better condensate drainage characteristic and to delay the required time for frosting. By using a hydrophilic and hydrophobic mixed thorn-shaped surface created by screen printing, the design makes use of the differences in the wettability gradient to achieve rapid condensate drainage and to lengthen the time for frosting. The results of a frosting experiment indicated that the droplet adsorption and combination and discharge effect in the thorn sample were substantial. The drainage effect increased the surface renewal rate and inhibited ice layer growth on the thorn sample by 52.4% compared with that on pure copper surface. The heat transfer coefficient of the thorn sample during frosting was approximately 16.2% higher than that of pure copper surface. In addition, the defrosting results indicated that the defrosting time of the thorn sample was almost equal to that of the pure copper sample. However, large droplets were easily stagnated at the structural junction due to contact angle hysteresis after defrosting.

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“…In these techniques, vapor is condensed to form droplets on a substrate surface through elaborate microscopic wettability patterning, 1,2 the structure of which is oen inspired by living organisms. [3][4][5][6] Another important element in water harvesting following vapor condensation is the collection of condensed droplets from a large area of substrate surface. Generally, gravity has been used to drive transfer of condensed droplets into a collection reservoir; [5][6][7] little attention has been paid to active long-range transport of water droplets.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6] Another important element in water harvesting following vapor condensation is the collection of condensed droplets from a large area of substrate surface. Generally, gravity has been used to drive transfer of condensed droplets into a collection reservoir; [5][6][7] little attention has been paid to active long-range transport of water droplets. 8 Recently, there has been progress in open microuidics designed to directionally transport liquid on a surface by means of wettability and topography patterning.…”

Section: Introductionmentioning

confidence: 99%

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Space-filling open microfluidic channels designed to collect water droplets

2018

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Key design and operating parameters for enhancing dropwise condensation through wettability patterning

Cited by 137 publications

References 44 publications

Lattice Boltzmann simulations for transition from dropwise to filmwise condensation on hydrophobic surfaces with hydrophilic spots

Lattice Boltzmann simulations for transition from dropwise to filmwise condensation on hydrophobic surfaces with hydrophilic spots

Visualization of Patterned Modified Surfaces in Condensation and Frosting States

Space-filling open microfluidic channels designed to collect water droplets

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