Droplet Condensation on Surfaces with Special Wettability†

doi:10.7503/cjcu20180820

Abstract

Abstract:

The surfaces with micro/nano structures were fabricated by electrochemical corrosion and then boiling water treatment. Superhydrophobic surface was fabricated by chemical vapor deposition. Hydrophobic and hydrophilic surfaces were fabricated by coating surfaces with silicon oil and hydroxy-terminated silicon oil. Condensation on these surfaces (superhydrophilic, superhydrophobic, hydrophobic slippery and hydrophilic slippery) were investigated. Superhydrophilic surfaces show filmwise condensation. Both super hydrophobic and slippery surfaces show dropwise condensation. Superhydrophobic surfaces show out-of-plane jumping motion of the coalesced drops. Due to the wettability difference between the hydrophobic slippery surface and hydrophilic surface, fast droplet coalescence on hydrophilic slippery surfaces can effectively increase the droplet volume over time. The fog harvesting rates of different surfaces ranged in turn are hydrophilic slippery, hydrophobic slippery, superhydrophilic and superhydrophobic.

Key words: Special wettability, Droplet condensation, Electrochemical corrosion, Micro/nano structures

CLC Number:

O647

TrendMD:

LIN Yucai,PEI Wenle,SUN Ruoxuan,GAO Chunlei,CHEN Jipeng,ZHENG Yongmei. Droplet Condensation on Surfaces with Special Wettability^†[J]. Chem. J. Chinese Universities, 2019, 40(6): 1236.

Figures/Tables 6

Fig.1 Fabrication processes of micro/nano structures(A) and SEM images of the original Al plate(B), the Al plate after electrochemical corrosion(C), the Al plate after boiling water treatment(D), and the nano-sturctures on the micro-structures after boiling water treatment(E)

Fig.2 Wettability of the surfaces (A) Superhydrophilic surface; (B) superhydrophobic surface; (C) hydrophobic surface slippery; (D) hydrophilic slippery surface.

Fig.3 Relationship between the conact angles/sliding angles and the wettability of the surfaces a. Superhydrophilic; b. superthydrophobic; c. hydrophilic slippory; d. hydrophobic slippery.

Fig.4 Water condensation on the surfaces with different wettabilities (A1—A5) Condensation on superhydrophilic surfaces; (B1—B5) condensation on superhydrophobic surfaces drops; (C1—C5) condensation oN hydrophobic surface, (D1—D5) condensation on hydrophilic surface. Time/s: (A1—D1) 0; (A2—D2) 150; (A3—D3) 300; (A4—D4) 450; (A5—D5) 600.

Fig.5 Sequential images of coalescence and bouncing behaviors of two droplets on superhydrophobic surface Time/ms: (A) 0; (B) 12; (C) 18; (D) 26.

Fig.6 Comparison of fog harvesting ability of four kinds of surface with different wettability (A) The relationship between the average diameter of largest droplet and the condensation time; (B) the relationship between the water colle-cted on different surfaces and the fog harvesting time.

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