Compositive effects of orientation and contact angle on critical heat flux in pool boiling of water

An experimental study was carried out to investigate the effects of heat transfer surface orientation and the solid-liquid contact angle on the boiling heat transfer and critical heat flux (CHF) in water pool boiling using a smooth heat-transfer surface under atmospheric pressure. The orientation angle was ranged from 0 degrees (up-facing horizontal position) to 180 degrees (down-facing horizontal position) with a pace of 45 degrees. The three kinds of heat transfer surfaces having different solid-liquid contact angles were the normal surface with a contact angle of 55 degrees, the hydrophilic surface with a contact angle of 30 degrees and the superhydrophilic surface with a contact angle of 0 degrees. The experimental results indicate that orientation and contact angle have complex, coupling effects on heat transfer and CHF. A predicting correlation for the CHF which takes the effects of both orientation and contact angle into account is established. The predicting correlation agrees reasonably well with the experimental data.