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Heat Transfer on Hierarchical Structured Graphite Composites
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  • Raphael Raab,
  • Tobias Melchior,
  • Hannah Mennecke,
  • Daniel Fotachov,
  • Egbert Oesterschulze,
  • Thomas Reviol,
  • Erik von Harbou,
  • Hans-Jörg Bart
Raphael Raab
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Tobias Melchior
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Hannah Mennecke
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Daniel Fotachov
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Egbert Oesterschulze
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Thomas Reviol
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Erik von Harbou
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau
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Hans-Jörg Bart
Rheinland-Pfalzische Technische Universitat Kaiserslautern-Landau

Corresponding Author:[email protected]

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Abstract

This study investigates the wetting behavior, condensation dynamics, and heat transfer performance of stainless steel (SS), graphite composite (GC), and a modified superhydrophobic graphite composite (SHGC) under varying relative humidity (RH) conditions. Static and dynamic contact angle measurements revealed significant differences in wetting behavior, with SS demonstrating hydrophilic properties ( 6 5 ◦ ± 7 ◦ ), GC exhibiting hydrophobicity ( 9 7 ◦ ± 2 ◦ ), and SHGC achieving superhydrophobicity ( > 1 7 0 ◦ ). Condensation experiments at 100% RH showed that GC and SHGC outperformed SS in both heat flux densities and heat transfer coefficients (HTCs) at higher RH levels. At 100% RH, GC achieved the highest heat transfer coefficient of 3 0 9 W / m 2 K ± 2 . 3 % , followed by SHGC 2 4 4 W / m 2 K ± 2 . 9 % , while SS remained at 1 3 4 W / m 2 K ± 6 . 5 % compared to 60 % and 80 % RH. Computational fluid dynamics simulations confirmed the experimental findings, validating laminar flow and demonstrating strong agreement with measured vapor-side HTCs. The reduced performance of SHGC compared to GC is attributed to the Wenzel pinning effect and additional thermal resistances. These findings highlight the need for further optimization of surface structure and coating uniformity to enhance the condensation heat transfer performance of SHGC in practical applications.