Investigation of coalescence-induced droplet jumping on superhydrophobic surfaces and liquid condensate adhesion on slit and plain fins

• Droplet jumping on complex textured surface is simulated by 3D MRT lattice Boltzmann method.
• Roughness of textured surface affects spontaneous jumping of coalesced droplet.
• More superhydrophobic textured surface is of advantage to induce higher jumping height.
• More hydrophilic or hydrophobic coatings are both helpful to avoid liquid bridge between fins.
• Coating is required more strictly for slit fin than for plain fin to avoid liquid bridge.

The coalescence-induced droplet jumping on superhydrophobic complex textured surface, as well as the liquid condensate adhesion on slit and plain fins with hydrophobic and hydrophilic coatings in the tube-and-fin heat exchanger is studied numerically using the three-dimensional multi-relaxation-time (MRT) pseudopotential lattice Boltzmann model. It is found that the height of the surface conical posts, the spacing between the consecutive conical posts, the number of the droplets, the radius of the droplet, and the wettability property of the complex textured surface have important effect on the spontaneous jumping of the coalesced droplet. For the liquid condensate adhesion on slit and plain fins, it is found that both the hydrophilic coating with small contact angle and the hydrophobic coating with large contact angle are effective on avoiding liquid bridge between fins. Furthermore, the coating is required more strictly for slit fin than for plain fin to avoid liquid bridge.