Toward enhancement of water vapour condensation using wettability gradient surface

• Effect of contact angle hysteresis is quantified on independant experimental results.
• Effect of this contact angle hysteresis is found to be important on the dynamic of the droplet.
• Spatial heterogeneities of contact angle hysteresis have also to be taken into account.
• Wettability gradient allows to maintain a dropwise condensation regime and thus to enhance the heat transfer.

This paper focuses on the behaviour of a liquid droplet on the surface of a treated solid substrate. We deal with the use of surface tension forces induced by heterogeneous wettability to allow the removal of the droplet. Our main aim is to present a new model able to predict the motion of a droplet of known volume along a wettability gradient taking into account the contact angle hysteresis: a key parameter in the dynamics of the droplet.