04. Boiling and Multi-Phase Flow

Finned tubes are widely used for condensation heat transfer in industrial processes and air-conditioning/refrigeration systems. Since the work of Beatty and Katz (1948), several rational and empirical correlations have been proposed to predict condensation heat transfer performance on integral-fin tubes. These correlations take into account tube geometries, fluid properties, and flow conditions. Due to the rapid development of material technologies, high conductivity and robust surface treatment have been developed in recent years. These low-surface-energy material coatings have been tested to increase the liquid-surface contact angle. Chen et al. (2019) applied graphene and fluorinated graphene coating on integral-fin tubes to enhance their condensation heat transfer coefficients by up to 47% compared to uncoated tubes. However, existing correlations do not account for the effect of liquid-surface contact angle and cannot adequately predict the effect of contact angle on condensation heat transfer. This study proposes a new correlation for condensation heat transfer on integral-fin tubes by considering the effect of the contact angle between liquid and surfaces. The forces acting on condensate accumulated within the fin spaces have been carefully considered and analyzed. This correlation has been examined using data from Chen et al. (2019) with reasonable agreement.