A novel composite adsorbent coated superhydrophilic-nanostructured heterogeneous surface for condensation heat transfer enhancement

In this work, a novel composite adsorbent coated superhydrophilic-nanostructured heterogeneous surface is proposed to enhance condensation heat transfer. Experiments are conducted under the atmospheric pressure condition with the ambient temperature of 23 ± 2 °C to investigate the water vapor condensation rate of the heterogeneous surfaces coated with different patterns of the composite adsorbent. The condensation rates and the latent heat transfer coefficients of the heterogeneous surfaces are investigated under the quiescent environment. The results show that the heterogeneous surfaces with vertical middle-stripe patterns of the composite adsorbent have better condensation heat transfer performance than the other patterns, showing 45.5%–80.0% improvement compared to the copper surface. It is found that during water condensation on the heterogeneous surfaces, the water film on the superhydrophilic region can be adsorbed by the adjacent composite adsorbent. Consequently, a water-free region is observed on the proposed heterogeneous surfaces, which provides extra fresh nucleation sites for water condensation, leading to an enhancement in the heat transfer performance. Based on this observation, a water film adsorption mechanism is introduced to explain the condensation heat transfer enhancement on the proposed heterogeneous surface, providing a practical and scalable surface treatment method to improve the condensation heat transfer.