Wetting characteristics of ethane droplet-A molecular dynamics study

The wettability significantly affects condensation heat transfer of alkanes on the surface. When designing high-efficiency heat exchangers, it is necessary to grasp the wetting patterns of alkanes. Therefore, the wetting characteristics of ethane droplets on the surface are investigated based on molecular dynamics simulation. The results show that the contact angle of pure ethane droplet reduces as the surface potential energy depth parameter e increases. The contact angle of pure ethane is larger than that of pure methane under the same e, and the difference augments with the increasing e. The enhanced molecular thermal motion caused by the rise in temperature produces different orientation outcomes on different VDW-functioned surfaces. The cumulative effect of molecular movement leads to a macroscopic displacement of the droplet, which makes the contact angle of pure ethane augment on hydrophobic surface, remain constant on neutral surface, and decrease on hydrophilic surface, meaning that the rise in temperature will strengthen the wetting tendency of pure ethane droplet. The addition of methane to ethane droplet acts as a "lubricant", resulting in local molecular activation and an increase in diffusion. The contact angles of mixed droplets on hydrophobic, neutral, and hydrophilic surfaces all decrease linearly with the increasing methane concentration. And the larger the contact angle gap between methane and ethane on the same surface, the larger the decrease in the contact angle of mixed droplets. This paper investigates the wetting characteristics and corresponding mechanisms of alkane droplets from a microscopic aspect, aiming to guide the design and development of high-efficiency heat exchangers.(c) 2022 Elsevier B.V. All rights reserved.