Observation and description of the shape of water bridge retaining between vertical plane surfaces

As the shape of water bridge retaining between vertical fins affects the performance of fin and-tube heat exchangers, it is necessary to investigate water bridge shape and to develop description methods for water bridge, including those for contact line and contact angles. In this study, a visual experimental apparatus for observing the shapes of water bridges between vertical plane surfaces was designed, and the contact lines and the contact angles for water bridges on 7 types of plane surfaces made of aluminum, copper, stainless steel, quartz glass, acrylic plastics, Teflon and hydrophobic modified copper were measured. The test conditions cover water bridge volumes of 3-21 mu L, and plane surface separations of 0.5-2.0 mm. The description method of water bridge shape is presented and compared with experimental data, including the description method of contact line with mean deviation of 2.2%, and the description method of contact angles with mean deviation of 6.1%. (C) 2016 Elsevier Ltd and IIR. All rights reserved.