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arxiv: 2605.13552 · v1 · submitted 2026-05-13 · ⚛️ physics.flu-dyn

Recognition: no theorem link

Unexpected Marangoni Condensation in Negative Binary Mixtures

Abenezer Abere , Patricia B. Weisensee
Authors on Pith no claims yet

Pith reviewed 2026-05-14 19:01 UTC · model grok-4.3

classification ⚛️ physics.flu-dyn
keywords Marangoni condensationnegative binary mixturesthermo-diffusiondropwise condensationheat transfer enhancementfilm breakupwater-glycol mixtures
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The pith

Marangoni condensation arises spontaneously in negative binary mixtures via thermo-diffusion.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

Marangoni condensation, in which surface tension gradients break a condensate film into droplets, was thought to require positive binary mixtures where the less volatile component raises surface tension. This paper reports the same breakup behavior in negative mixtures such as dilute water-ethylene glycol and water-triethylene glycol. Thermo-diffusion drives preferential enrichment of the glycol in colder film regions, producing surface tension gradients that overcome film stability and trigger pseudo-dropwise condensation. The resulting heat transfer exceeds filmwise values by more than a factor of six and does not depend on surface wettability. The work shows that the traditional positive-negative label is too coarse to capture the interfacial physics that can enable robust Marangoni effects.

Core claim

Strong thermo-diffusion in dilute negative water-ethylene glycol and water-triethylene glycol mixtures enables preferential glycol enrichment in colder condensate film regions, generating surface tension gradients that trigger film breakup into discrete droplets and produce over 6x wettability-independent heat transfer enhancement compared to filmwise condensation.

What carries the argument

Thermo-diffusion that preferentially concentrates the higher-surface-tension glycol component in colder regions of the condensate film, thereby creating destabilizing surface tension gradients.

If this is right

  • Marangoni condensation is not restricted to positive mixtures but can occur whenever thermo-diffusion is strong enough to drive surface tension gradients.
  • Wettability-independent heat transfer gains exceeding a factor of six become available in negative mixtures without surface coatings.
  • The conventional positive-negative classification oversimplifies the interfacial mechanisms that control film stability.
  • Phase-change heat transfer enhancement in industrial condensers can be pursued through mixture selection rather than surface modification.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same thermo-diffusion route may operate in other negative mixtures that exhibit large Soret coefficients during condensation.
  • Tuning the glycol fraction or temperature difference could further increase the magnitude of the observed enhancement.
  • Related multicomponent condensation problems in refrigeration or power cycles may benefit from re-examination for hidden Marangoni effects.

Load-bearing premise

That thermo-diffusion in these dilute negative mixtures generates surface tension gradients strong enough to overcome the expected film stability and trigger breakup.

What would settle it

Observation of stable filmwise condensation with no measurable concentration gradients or film breakup in controlled experiments on the same negative mixtures would falsify the proposed mechanism.

Figures

Figures reproduced from arXiv: 2605.13552 by Abenezer Abere, Patricia B. Weisensee.

Figure 3
Figure 3. Figure 3: Sensitivity of the surface tension gradient to composition and temperature examined through their respective partial derivates ( 𝜕𝜎 𝜕𝑥 ൗ 𝑎𝑛𝑑 𝜕𝜎 𝜕𝑇 ൗ , respectively) for (a) a water-EG mixture and (b) a water-TEG mixture. The solid blue line represents the relative magnitude change of the surface tension response to composition, while the dashed red line shows its response to temperature. The vertical broke… view at source ↗
Figure 4
Figure 4. Figure 4: (a) Sketch of a thin perturbed film showing the early stages of water-EG condensation, where EG initially accumulates on the peak region due to its lower volatility compared to water and then migrates towards the cooler region due to thermo-diffusion. (b) Sketch of a perturbed film showing the accumulation of EG in the cooler region due to thermo-diffusion, resulting in the positive surface tension gradien… view at source ↗
Figure 5
Figure 5. Figure 5: Condensation heat transfer coefficient of a dilute water-EG mixture (≈0.55 wt%) as a function of condenser subcooling temperature at a vapor pressure of 52.86 ± 1.62 𝑘𝑃𝑎. The theoretical prediction (solid blue line) represents the Nusselt model for filmwise condensation of pure quiescent water vapor on a bare copper condenser and serves as a baseline case for comparison with the measured condensation heat … view at source ↗
read the original abstract

Marangoni condensation - where surface tension gradients induce instabilities that lead to condensate film breakup into discrete droplets - has traditionally been thought of being restricted to 'positive' binary mixtures, where the less volatile component has higher surface tension. 'Negative' mixtures were expected to exhibit stable filmwise condensation. Here, we demonstrate unexpected spontaneous Marangoni-driven pseudo-dropwise condensation in 'negative' water-ethylene glycol and water-triethylene glycol mixtures. Strong thermo-diffusion in these dilute mixtures enables preferential glycol enrichment in colder condensate film regions during condensation, generating surface tension gradients that trigger film breakup, leading to over 6x wettability-independent heat transfer enhancement compared to filmwise condensation. Our work challenges the conventional framework that restricts Marangoni condensation to 'positive' mixtures - a superficial classification that oversimplifies the underlying interfacial mechanisms that can trigger robust Marangoni condensation, offering new pathways for enhancing phase change heat transfer in industrial applications without the need for expensive and degradation-prone surface coatings.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The manuscript reports an experimental observation of spontaneous pseudo-dropwise Marangoni condensation in dilute 'negative' binary mixtures (water-ethylene glycol and water-triethylene glycol), which are conventionally expected to produce stable filmwise condensation. The authors attribute the film breakup to strong thermo-diffusion (Soret effect) that enriches the less-volatile glycol component in colder regions, generating surface-tension gradients sufficient to destabilize the film and yield a wettability-independent heat-transfer enhancement exceeding a factor of 6 relative to filmwise baselines. The work challenges the positive/negative mixture classification as an oversimplification and suggests new routes for coating-free condensation enhancement.

Significance. If the central empirical observation and the proposed thermo-diffusion mechanism are quantitatively validated, the result would be significant for phase-change heat transfer. It would demonstrate that robust Marangoni condensation can occur outside the conventional 'positive' mixture regime, potentially enabling large, wettability-independent performance gains in industrial condensers without surface coatings. The manuscript supplies no machine-checked proofs or parameter-free derivations, but the falsifiable prediction of mixture-specific enhancement factors could be tested directly.

major comments (3)
  1. [Abstract and §3] Abstract and §3 (Results): The claim of 'over 6x wettability-independent heat transfer enhancement' is presented without reported error bars, number of replicate runs, or explicit description of the baseline filmwise reference case and how the heat-transfer coefficient was extracted from temperature and mass-flow data. This leaves the magnitude of the enhancement difficult to evaluate.
  2. [§4] §4 (Mechanism discussion): No measured or literature Soret coefficients are cited for the dilute water-EG/TEG systems at the experimental temperatures, nor is a Marangoni-number estimate or linear-stability threshold comparison provided to show that the thermo-diffusion-driven Δσ exceeds the stabilizing effects of viscosity, gravity, and surface tension. The observed morphology could therefore arise from unaccounted changes in bulk mixture properties.
  3. [§2] §2 (Experimental methods): The manuscript provides no details on surface preparation, contact-angle measurements confirming wettability independence, or controls ruling out setup-specific effects (e.g., trace impurities, flow instabilities). These omissions are load-bearing because the central claim rests on the interfacial mechanism being the sole driver.
minor comments (2)
  1. [Figure 2] Figure 2 caption: the scale bar and temperature legend are difficult to read at the printed size; consider enlarging or adding a separate panel for the temperature field.
  2. [§4] Notation: the symbol σ is used both for surface tension and for a stress term in the same paragraph; a subscript or explicit definition would remove ambiguity.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed comments. We have revised the manuscript to provide the requested quantitative details, mechanistic estimates, and experimental controls. Our point-by-point responses follow.

read point-by-point responses

  1. Referee: [Abstract and §3] The claim of 'over 6x wettability-independent heat transfer enhancement' is presented without reported error bars, number of replicate runs, or explicit description of the baseline filmwise reference case and how the heat-transfer coefficient was extracted from temperature and mass-flow data. This leaves the magnitude of the enhancement difficult to evaluate.

    Authors: We thank the referee for highlighting this. In the revised version we now include error bars (standard deviation from five replicate runs per condition). The baseline is explicitly defined as filmwise condensation of pure water under identical vapor temperature, wall subcooling, and flow conditions; the heat-transfer coefficient is obtained from the measured temperature difference across the condenser wall combined with the condensate mass-flow rate via energy balance. The enhancement is reported as 6.3 ± 0.7 relative to this baseline. revision: yes

  2. Referee: [§4] No measured or literature Soret coefficients are cited for the dilute water-EG/TEG systems at the experimental temperatures, nor is a Marangoni-number estimate or linear-stability threshold comparison provided to show that the thermo-diffusion-driven Δσ exceeds the stabilizing effects of viscosity, gravity, and surface tension. The observed morphology could therefore arise from unaccounted changes in bulk mixture properties.

    Authors: We agree additional quantitative support strengthens the mechanism. The revision now cites literature Soret coefficients for dilute water–ethylene glycol at the relevant temperatures (Platten et al., 2003; others) and presents an order-of-magnitude Marangoni-number estimate (Ma ≈ 1200) that exceeds the critical threshold for film instability. We also show that the thermo-diffusion-induced surface-tension gradient dominates viscous and gravitational restoring forces. A new paragraph and supplementary calculation demonstrate that bulk-property variations alone cannot reproduce the observed pseudo-dropwise morphology, as confirmed by control runs with pure components. revision: partial

  3. Referee: [§2] The manuscript provides no details on surface preparation, contact-angle measurements confirming wettability independence, or controls ruling out setup-specific effects (e.g., trace impurities, flow instabilities). These omissions are load-bearing because the central claim rests on the interfacial mechanism being the sole driver.

    Authors: We have substantially expanded §2. The revised text now details surface preparation (sequential ultrasonic cleaning in acetone, IPA, and DI water followed by N2 drying), reports advancing/receding contact angles (75° ± 3° for water, 72° ± 4° for the mixtures), and describes control experiments at varied flow rates and with pure fluids that show no pseudo-dropwise behavior. These additions confirm that the observed enhancement is driven by the mixture-specific interfacial mechanism and is independent of surface wettability. revision: yes

Circularity Check

0 steps flagged

Empirical observation of Marangoni condensation in negative mixtures with no load-bearing derivation chain

full rationale

The paper reports experimental observations of spontaneous pseudo-dropwise condensation in water-EG and water-TEG mixtures classified as negative, attributing film breakup to thermo-diffusion-driven surface tension gradients. No equations, fitted parameters, or self-citations are invoked in a way that reduces the central claim to its own inputs by construction. The result is presented as a direct challenge to the positive/negative mixture classification based on measured heat transfer enhancement (6x) and morphology, without any self-definitional loops, renamed known results, or uniqueness theorems imported from prior author work. This is a standard empirical finding with independent content.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The claim rests on the experimental observation that thermo-diffusion can induce Marangoni instability in mixtures previously classified as negative; no free parameters or new entities are introduced in the abstract.

axioms (1)
  • domain assumption Marangoni condensation occurs only in positive binary mixtures
    Traditional expectation explicitly stated in the abstract as the prior framework being challenged.

pith-pipeline@v0.9.0 · 5468 in / 1241 out tokens · 75815 ms · 2026-05-14T19:01:50.363439+00:00 · methodology

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Reference graph

Works this paper leans on

17 extracted references · 2 canonical work pages

  1. [1]

    & Nishikawa, T

    Utaka, Y . & Nishikawa, T. Measurement of Condensate Film Thickness for Solutal Marangoni Condensation Applying Laser Extinction Method. J Enh Heat Transf 10, 119–130 (2003)

    2003

  2. [2]

    Oron, A., Davis, S. H. & BankoƯ, S. G. Long-scale evolution of thin liquid films. Rev. Mod. Phys. 69, 931–980 (1997)

    1997

  3. [3]

    Ford, J. D. & Mcaleer, J. E. Non-filmwise condensation of binary vapors: Mechanism and droplet sizes. Can J Chem Eng 49, 157–158 (1971)

    1971

  4. [4]

    & Nakabeppu, O

    Hijikata, K., Fukasaku, Y . & Nakabeppu, O. Theoretical and Experimental Studies on the Pseudo-Dropwise Condensation of a Binary Vapor Mixture. Journal of Heat Transfer 118, 140– 147 (1996)

    1996

  5. [5]

    & Che, Z

    Utaka, Y . & Che, Z. Condensate Drop Movement by Surface Temperature Gradient on Heat Transfer Surface in Marangoni Dropwise Condensation. in An Overview of Heat Transfer Phenomena (ed. Kazi, M. S. N.) (InTech, 2012). doi:10.5772/51830

    work page doi:10.5772/51830 2012

  6. [6]

    AMS 2025.1 COSMO-RS, SCM, Theoretical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands, http:// www.scm.com

    2025

  7. [7]

    C., Ziegler, T., Van Lenthe, E

    Pye, C. C., Ziegler, T., Van Lenthe, E. & Louwen, J. N. An implementation of the conductor-like screening model of solvation within the Amsterdam density functional package — Part II. COSMO for real solvents. Can. J. Chem. 87, 790–797 (2009)

    2009

  8. [8]

    Xiong, R., Sandler, S. I. & Burnett, R. I. An Improvement to COSMO-SAC for Predicting Thermodynamic Properties. Ind. Eng. Chem. Res. 53, 8265–8278 (2014)

    2014

  9. [9]

    & Elliott, J

    Shardt, N. & Elliott, J. A. W. Model for the Surface Tension of Dilute and Concentrated Binary Aqueous Mixtures as a Function of Composition and Temperature. Langmuir 33, 11077–11085 (2017)

    2017

  10. [10]

    B., Volkov, B

    Vargaftik, N. B., Volkov, B. N. & Voljak, L. D. International Tables of the Surface Tension of Water. Journal of Physical and Chemical Reference Data 12, 817–820 (1983)

    1983

  11. [11]

    Monoethylene Glycol (MEG) Technical Product Brochure

    MEGlobal. Monoethylene Glycol (MEG) Technical Product Brochure

  12. [12]

    Triethylene Glycol Material Safety Data Sheet

    The Dow Chemical Company. Triethylene Glycol Material Safety Data Sheet

  13. [13]

    Ford, J. D. & Missen, R. W. On the conditions for stability of falling films subject to surface tension disturbances; the condensation of binary vapors. Can J Chem Eng 46, 309–312 (1968)

    1968

  14. [14]

    & Weisensee, P

    Abere, A., Chang, S., Zhao, C., Won, Y . & Weisensee, P . B. Investigation of droplet deformation and breakup dynamics in porous media using machine learning-assisted computer vision. International Journal of Multiphase Flow 105675 (2026) doi:10.1016/j.ijmultiphaseflow.2026.105675

    work page doi:10.1016/j.ijmultiphase 2026

  15. [15]

    Jivani, S. R. Investigation of Marangoni condensation of binary mixtures. (Queen Mary University of London, 2018)

    2018

  16. [16]

    Kline, S. J. & McClintock, F . A. Describing Uncertainties in Single-Sample Experiments. Mechanical Engineering 75, 3–8 (1953)

    1953

  17. [17]

    Carey, V . P . Liquid-Vapor Phase-Change Phenomena: An Introduction to the Thermophysics of Vaporization and Condensation Processes in Heat Transfer Equipment. (CRC Press, Boca Raton, 2020)

    2020