Flow boiling heat transfer in wettability patterned microchannels

A wettability patterned surface has been developed to manipulate nucleation boiling in a micro fluid flow channel. The wettability patterns was fabricated by using hydrophobic dots on hydrophilic surfaces which form non-wetting islands and wetting network. The hydrophobic hexagon dots with a side length of 30μm and pitch distance 60μm are fabricated with Teflon (Teflon AF 400s2-100-1, DuPont) which has a contact angle of 120 degree. Experiments were conducted for flow boiling in a microchannel. The effects of wettability patterned surfaces on fluid flow, bubble generation and detachment in a microchannel will be visualized/measured utilizing micro resolution particle image velocimetry. The effects of surface patterns on bubble size, heat flux and heat transfer coefficient in flow boiling heat transfer processes were visualized by high speed camera and temperature sensors. It was found that on the wettability patterned surface, the temperature for onset nucleate boiling is about 6°C lower than that on the homogeneous surface while the heat transfer coefficient is about 70% higher than the hydrophilic surface. The results shows that the heat transfer can be significantly enhanced by wettability patterns in comparison with a hydrophilic surface under flow boiling conditions.