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Dynamics of frost growth on vertical superhydrophobic surfaces.

Number: pap. 2408

Author(s) : BOYINA K. S., RABBI K. F., SU W., et al.

Summary

Superhydrophobic surfaces, which promote the efficient removal of condensing droplets prior to supercooling and freezing through coalescence induced jumping, have been shown to delay frosting significantly. The performance of fin and tube heat exchangers used in refrigeration and heat pump applications has the potential for improvement when coated with suitably designed superhydrophobic coatings. Currently, state-of-the-art (SOA) fins and their spacing are designed carefully to optimize pressure drop and heat transfer. Understanding the effect of fin spacing on frost growth on surfaces with different wettabilities is important when designing next-generation heat exchangers. In our work, condensation/frost interaction between two parallel superhydrophobic surfaces was studied experimentally. Frost growth on two aluminum superhydrophobic surfaces (150 mm × 90 mm) was tested under different conditions: surface temperature Ts =-5.0°C, -10.0°C and -15.0°C; surface spacing of 2mm, 4mm, 6mm, and 8mm; ambient temperature Tamb = 25.0°C, and relative humidity RHamb ˜ 50-70%. Frost growth was recorded via high resolution optical imaging from the side and top of the gap between the surfaces. Average frost thickness was measured visually by analyzing high resolution and high contrast images of the edge of the cold plates. Tests were also performed for bare aluminum (hydrophilic) and superhydrophilic surfaces under the same conditions for comparison. Results showed that frost grew in two different regimes. Frost growth rates for the superhydrophobic surfaces were lower than the hydrophilic and superhydrophilic surfaces due to the difference in the density of the frost layers. Our work not only contributes valuable data that can be used to optimize the design of coated heat exchangers, it elucidates the complex thermodynamics governing the condensation frosting process on heat exchangers.

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Pages: 10

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Details

  • Original title: Dynamics of frost growth on vertical superhydrophobic surfaces.
  • Record ID : 30024540
  • Languages: English
  • Source: 2018 Purdue Conferences. 17th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2018/07/09

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