Tuning the wettability of wire mesh column: pore-scale flow analysis

The pore-scale behaviour of liquid flow over wire mesh stainless-steel packing of variable contact angle is relevant for mass and heat exchanges in multiphase chemical systems. This behaviour was investigated by imaging experiments and 3D volume-of-fluid modelling. The surface of the wire mesh ring was modified by alumina coating to reach both hydrophilic and hydrophobic characteristics. The cycle of capillary droplet flow over the uncoated ring exhibited penetration of the hydrophilic mesh openings, adherence to the surface of the ring and accumulation as drips at the bottom region of the rings. However, over the hydrophobic ring, the droplet exhibited low adherence to the ring surface, accumulation at the top surface of the ring, no penetration of the openings, slip by the gravitational forces over the vertical curvature and accumulation as drips at the bottom region. In agreement with the classical observations at the macroscale, the observations at the pore-scale confirmed the increase of the wetting efficiency, liquid holdup and effective surface area at increased liquid flowrate and reduced contact angle. The 3D model was in reasonable agreement with Stichlmair's model for the liquid holdup, particularly in the hydrophilic zone of the contact angle and low flow as well as in a reasonable agreement with Linek's model for effective area, particularly in the hydrophobic range of the contact angle.