Moist air condensation heat transfer enhancement via superhydrophobicity

The main objective of the present study is to experimentally investigate the moist air condensation be-havior subject to hydrophilic and superhydrophobic surface with a much broader operating conditions such as different relative humidities (RH = 40 - 85%) and degree of subcooling (Delta T-sub = 1 - 16 K). The flow visualization of condensation behavior showed that the main condensate departure mechanism of the hydrophilic surfaces is gravity-driven sliding. In contrast, the primary mechanisms for the superhy-drophobic surfaces are direct jumping and bounced-jumping caused by the coalescence induced phenom-ena. The superhydrophobic surfaces yielded a maximum of 36% improvement in heat transfer coefficient at 85% relative humidity over the hydrophilic surfaces, while the enhancement is about 16% for 60% and 40% relative humidities. Similarly, the maximum heat transfer coefficient of 37 W m(-2) K-1 is attained at the subcooling temperature of 16 K, and it is reduced to 31 W m(-2) K-1 and 20 W m(-2) K-1 respectively when the subcooling is reduced to 6 K and 1 K. (c) 2021 Elsevier Ltd. All rights reserved.