Dynamic Defrosting on Superhydrophobic and Biphilic Surfaces

Yashraj Gurumukhi, Shreyas Chavan, Soumyadip Sett, Kalyan Boyina, Srivasupradha Ramesh, Peter Sokalski, Kirk Fortelka, Maury Lira, Deokgeun Park, Juo Yun Chen, Shreyas Hegde, Nenad Miljkovic

Research output: Contribution to journalArticlepeer-review

Abstract

Ice formation and accretion present serious concerns for many building energy applications. Current defrosting methods expend significant energy by reversing the system cycle direction to heat the working fluid. Additionally, water retained on heat exchangers post defrosting cycle decreases the long-term heat-transfer performance. Here, we study the defrosting behavior of superhydrophobic and biphilic surfaces having spatially distinct wettability domains. Through optical imaging, we show that defrosting on biphilic regions is dynamic, where the ice/frost layer undergoes spontaneous motion because of a highly mobile slush. The high mobility of dynamic defrosting enables surface forces to “pull” and remove the slush from the superhydrophobic regions prior to it completely melting. To explore the effect of pattern heterogeneity, we studied nature-inspired biphilic patterns such as banana leaf. Our work provides the fundamental understanding required for design of heterogeneous defrosting coatings and elucidates the role of wettability gradients on defrosting dynamics. Defrosting of heat exchangers is a highly inefficient process. Coating heat exchangers with structured surfaces can improve defrosting performance. Such coatings have previously focused on delaying frost formation and reducing ice adhesion. Here, we study heterogeneous surfaces having spatially distinct regions of wettability, termed biphilic surfaces. The highly water-repellent regions enable the formation of a highly mobile slush, which moves toward the water-adhesive regions, quickly cleaning the former region of water. Water is then restricted to the water-adhesive regions, from where its evaporation rate is enhanced because of the higher length of the three-phase contact lines on biphilic surfaces. Biphilic surfaces can potentially outperform other surfaces in terms of defrosting and icing. When combined with suitable large-scale manufacturing methods, biphilic surfaces can have significant impact on the defrosting performance of heat exchangers. Efficiency of common active defrosting methods for heat exchangers is very low, but it can be improved through the use of engineered coatings on the surface. Homogeneous surfaces having different wettabilities are compared with biphilic surfaces in terms of surface cleaning and evaporation during defrosting. Enhanced defrosting performance of heterogeneous biphilic surfaces is demonstrated when compared with homogeneous surfaces. Fundamental understanding for design of biphilic surface coatings is developed.

Original languageEnglish (US)
Pages (from-to)1178-1195
Number of pages18
JournalMatter
Volume3
Issue number4
DOIs
StatePublished - Oct 7 2020

Keywords

  • MAP5: Improvement
  • biphilic surfaces
  • de-blooming
  • defrosting
  • hydrophilic
  • self-cleaning
  • superhydrophobic
  • water retention

ASJC Scopus subject areas

  • Materials Science(all)

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