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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

FROST MELTWATER BEHAVIORAL CHARACTERISTICS DURING DEFROSTING ON SURFACES WITH VARIOUS WETTABILITY

Get access (open in a dialog) DOI: 10.1615/IHTC16.rac.022346
pages 8471-8477

Аннотация

Frosting is a common phenomenon in refrigeration and cryogenic engineering systems. Since a frost layer reduces the heat transfer efficiency and blocks the flow channel, periodic defrosting is essential, and the defrosting characteristics of a frosted surface need to be understood to further improve the defrosting efficiency. In the present work, surfaces with various wettability were prepared with defrosting experiments conducted on these surfaces to study their frost meltwater behavioral characteristics. On the bare aluminum surface, the frost melts and fractures, forming into many isolated meltwater droplets with irregular shapes; on the hydrophobic surfaces, the frost meltwater breaks up and dewets into many spherical droplets with circular triple lines; on the superhydrophobic surface, the meltwater droplets have very high mobility with self-propelled jumping movements easily triggered by droplet shrinking. These different meltwater behavioral characteristics are controlled by the unbalanced Young force and the pinning force on the triple phase line of the meltwater droplet, and the unbalanced Young force and the pinning force are determined by the surface wettability including the surface contact angle and the contact angle hysteresis. In addition, surface coverages by the meltwater droplets after defrosting were counted. Due to the self-propelled movements, the average surface coverage is less than 10% on horizontal superhydrophobic surfaces, indicating a very good meltwater drainage performance.