Effects of Contact Angles of Nanoparticles on the Boiling Heat Transfer Coefficients

To study the effects of contact angles of various nanoparticles on the boiling heat transfer coefficients, a boiling experiment was conducted using SiO₂ nanofluids with different contact angles. By observing the sizes of the bubbles formed during boiling process and the morphology of the layers deposited on heated surface after boiling experiment, the effects of nanoparticles and their contact angles on the sizes of boiling bubbles and the morphology of deposited layers were studied, thus to further reveal the influence mechanism of the wettability of nanoparticles on the boiling heat transfer coefficients. Results show that the contact angles of nanoparticles would affect the stability of the bubbles formed in boiling process and the morphology of the layers deposited on heated surface, and different surface morphologies present different heat transfer effectiveness. Medium hydrophilic nanoparticles can be adsorbed on the gas-liquid interface of bubbles, producing enhanced heat transfer coefficients; whereas the medium hydrophilic nanoparticles deposited on the heated surface may increase the surface roughness, when more nucleation sites would be produced, resulting in improved heat transfer coefficients.