Effect of hydrophobic inclined patterns on pool boiling performance of cylindrical copper surfaces

In this study, a screen printing technique was used to fabricate heterogeneous wettable structures on a copper surface. The pool boiling heat transfer experiments were conducted on a hollowed copper cylinder of 25 mm outer diameter and 40 mm in length using deionized water as the working fluid. The effect of heterogeneous wettable surfaces with different inclination angles of the line patterns on the boiling heat transfer performance and bubble dynamics was investigated. Four different inclination angles of interlaced line patterns were evaluated: 0 degrees , 30 degrees , 60 degrees , and 90 degrees. The printed lines were parallel to the axial line of the cylinder for an inclination angle of 0 degrees. The highest heat transfer coefficient enhancements attained for the four angles were 89.27%, 104.59%, 103.99%, and 71.65%, respectively. Toward applications in microelectronics and heat exchangers, the effectiveness of interlaced patterns in a higher heat flux regime, i.e., above 80 kW/m(2), is also demonstrated. The surface with theta = 30 degrees pattern lines produced the best heat transfer performance due to the proper distance in the buoyancy direction, causing better bubble coalescence behavior and a better rewetting phenomenon.