Dropwise condensation heat transfer for ethanol on perfluoropolyether-coated copper disks

Al-Khateeb BWN, Vranjes F, Mensah GO, Mezhnev AN, Idrees MS, Khatir B, Au S, Golovin K, Rausch MH, Fröba AP (2026)

Publication Language: English

Publication Type: Journal article, Original article

Publication year: 2026

Journal

Book Volume: 178

Article Number: 111802

DOI: 10.1016/j.expthermflusci.2026.111802

Abstract

Dropwise condensation (DWC) heat transfer is known to be superior to that of filmwise condensation (FWC) but remains challenging to achieve for fluids with low surface tension. In this study, DWC of ethanol was promoted using a perfluoropolyether coating covalently bonded to diamond-milled copper disks by silica. Dynamic and static contact angles were measured with a custom-made experimental setup and corresponding image-analysis software to characterize the wettability of the surface with ethanol and to determine its surface free energy of about 11 mN⋅m⁻¹. Condensation heat transfer coefficients αcond were measured with a new apparatus for ethanol vapor pressures from (20 to 155)kPa and subcoolings from about (0.1 to 25)K. The thermal connection of the sample disks to the cooling system and the quantification of the associated thermal resistance were evaluated critically. The setup was validated successfully by comparing the measured αcond values for FWC on uncoated copper with the predictions of Nußelt’s film theory and by finite element simulations performed for the most critical regime of low subcoolings. For DWC at a given vapor pressure, αcond initially increases with increasing subcooling, followed by a decrease up to the transition to FWC at high cooling rates. This behavior for DWC as a function of subcooling is probably related to competing effects of increasing droplet dynamics and increasing amount of condensate present at the wall. For a given subcooling, αcond increases with increasing vapor pressure up to about 90 kPa, while αcond is approximately constant at higher pressures.

Authors with CRIS profile

Additional Organisation(s)

Related research project(s)

Involved external institutions

University of Toronto Canada (CA)

How to cite

APA:

Al-Khateeb, B.W.N., Vranjes, F., Mensah, G.O., Mezhnev, A.N., Idrees, M.S., Khatir, B.,... Fröba, A.P. (2026). Dropwise condensation heat transfer for ethanol on perfluoropolyether-coated copper disks. Experimental Thermal and Fluid Science, 178. https://doi.org/10.1016/j.expthermflusci.2026.111802

MLA:

Al-Khateeb, Baraá Wassefe Nabil, et al. "Dropwise condensation heat transfer for ethanol on perfluoropolyether-coated copper disks." Experimental Thermal and Fluid Science 178 (2026).

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