Performance of the frosting characteristics of fin-and-tube heat exchanger subject to superhydrophobic coating

• Published in: Applied thermal engineering Vol. 235; p. 121338
• Main Authors: Yang, Kai-Shing, Zheng, Jia-Wei, Wu, Kai-Lun, Wu, Yu-Lieh
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 25.11.2023
• Subjects: Fin-and-tube heat exchanger; Frosting characteristics; Superhydrophobic; Superhydrophobic; BAS; HTR; Frosting characteristics; CA; DB; SHPS; Fin-and-tube heat exchanger
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2023.121338

•Frost characteristics on bare and superhydrophobic surfaces are studied.•Superhydrophobic surface delays frosting by 4 h.•Two different frosting characteristics are indefied: sliding and non-sliding.•Superhydrophobic surface shows pronounced effect before frosting with a larger fin spacing.•Pressure drop in high-humidity decreases by 8.3% on superhydrophobic surface. The condensation and freezing processes of fin-and-tube heat exchangers with a bare surface and coated with a superhydrophobic substance were experimentally studied for various air velocities, relative humidity (RH) values, and fin spacings. The performance of the fin-and-tube heat exchangers in terms of dynamic pressure drop and heat transfer rate were reported in details. The frosting characteristics of these exchangers were visually characterized microscopically. It is found that for a superhydrophobic exchanger with 1-mm fin spacings, water bridges were likely to form, causing droplets to stick between the fins instead of slipping off the surface. At a low RH and a maximum air velocity of 1.0 m s−1, the heat transfer rate of the superhydrophobic exchanger was 12% lower than that of the surface without superhydrophobic coating. For a fin spacing of 3.0 mm, the critical droplet size was smaller than the fin spacing, hence the droplets can easily slip or jump off the fins. At a velocity of 0.6 m s−1, the steady-state pressure drop at low humidity of the superhydrophobic exchanger was 14% lower than that of the bare surface because of the differences in frosting characteristics. The results of this study indicate that the adopted superhydrophobic coating can delay frosting at high humidity and air velocity.