Method for calculating shape of PW-Cassie condensate droplet on super-hydrophobic surface

A calculation method and super-hydrophobic technology, applied in surface tension analysis, surface/boundary effects, measuring devices, etc., can solve problems such as errors and achieve good results

Pending Publication Date: 2021-07-13
ZHEJIANG UNIV OF TECH
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Problems solved by technology

Since the condensate droplets are in the micro-nano scale, the approximation of the shape will cause relatively large errors
Currently, there are very few computational methods that have investigated the exact contours of PW-Cassie droplets

Method used

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  • Method for calculating shape of PW-Cassie condensate droplet on super-hydrophobic surface
  • Method for calculating shape of PW-Cassie condensate droplet on super-hydrophobic surface
  • Method for calculating shape of PW-Cassie condensate droplet on super-hydrophobic surface

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Embodiment Construction

[0047] The present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

[0048] A kind of calculation method of PW-Cassie condensate droplet shape on the superhydrophobic surface of the present invention, comprises the following steps:

[0049] (1) Establish assumptions:

[0050]a. The equivalent radius of a PW-Cassie droplet is always smaller than the capillary length, where the capillary length where γ lv is the surface tension of the liquid and gas, ρ is the density of the liquid, and g is the acceleration due to gravity. For a water droplet at 20°C, the capillary length is about 2.7 mm. Therefore, the effect of gravity is ignored;

[0051] b. The surface tension of the droplet reaches equilibrium at the three-phase contact line, and the contact angle is the same as the Wen...

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Abstract

A method for calculating the shape of a PW-Cassie condensate droplet on a super-hydrophobic surface comprises the following steps: (1) establishing a calculation hypothesis; (2) establishing an isolated droplet system; (3) calculating the free energy of the isolated droplet system; (4) optimizing the free energy of the surface of the condensate droplet; (5) writing a program by utilizing a nonlinear optimization function fmincon in MATLAB software, and searching variables ui and vi (i = 1, 2,..., N + 1) to enable the free energy of the system to be minimum under the constraint; and recording the coordinates of the discrete point pi (ui, vi) corresponding to the minimum free energy, and fitting the discrete point pi (ui, vi) to obtain a profile curve. According to the method, the problem of calculation of the contour form of the PW-Cassie condensate droplets partially infiltrated on the super-hydrophobic surface is solved, the coincidence degree with experimental observation is better, and the method has extremely important guiding significance for theoretical research on heat transfer of the PW-Cassie condensate droplets on the super-hydrophobic surface and is expected to guide design of an efficient condensation heat transfer surface.

Description

technical field [0001] The invention belongs to the field of surface wettability, and relates to a method for calculating the shape of PW-Cassie condensate droplets on a superhydrophobic surface, in particular to a calculation method based on minimum free energy theory, finite difference method and nonlinear optimization algorithm to obtain PW-Cassie condensation Computational methods for droplet profile morphology. Background technique [0002] Condensation is a ubiquitous phenomenon in nature. Whether it is dew on the lawn or water droplets on the bathroom wall, it is formed by the phase change of latent heat released by water vapor when it comes into contact with a surface below its saturation temperature. Since the heat transfer coefficient of droplet condensation is 1 to 2 orders of magnitude higher than that of film condensation, it has more efficient heat transfer performance. However, due to different surface properties, condensate droplets will exhibit different we...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N13/00G01N13/02
CPCG01N13/00G01N13/02G01N2013/0208G01N2013/0283
Inventor 董健胡光辉赵逸平卞银波胡建良潘新科张王明郭有海
Owner ZHEJIANG UNIV OF TECH
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