Superhydrophobic fins with inclined arrangement for enhancing energy saving of air-cooled wet heat exchangers

Abstract

The energy consumption of the air-cooled heat exchangers such as evaporators operating under wet conditions is much higher owing to the condensate retention and bridging. The retained condensates and condensate bridging could narrow down the free airflow passage in the fin side and can adversely increase the airside pressure drop, which raises the fan power consumption. Effective condensate drainage can minimize the fan power consumption in such thermal management systems. Accordingly, this work proposes a superhydrophobic heat exchanger with an inclined fin arrangement that can effectively remove condensates and minimize the airside pressure drop. In this work, the departure droplet diameter of the untreated and superhydrophobic surfaces is predicted using the force balance analysis. A rationally based correlation is proposed to describe the condensate shedding ability of the different fin surfaces through dimensionless analysis. It is found that the departure droplet diameter of the superhydrophobic surfaces is almost 90% smaller than that of the untreated surfaces. The superhydrophobic fins offered remarkable condensate shedding characteristics. Consequently, the superhydrophobic heat exchangers with inclined fins provided a pressure drop reduction of up to 70%. The effect of inclination angle and the superhydrophobic coating on the heat transfer rate is negligible.