An integrated study of dropwise condensation heat transfer on self-assembled organic surfaces through Fourier transform infra-red spectroscopy and ellipsometry

Pang, Guoxin; Dale, J. D.; Kwok, Daniel Y.

doi:10.1016/j.ijheatmasstransfer.2004.08.029

Cited by 28 publications

(9 citation statements)

References 27 publications

(46 reference statements)

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“…Implications for Heat Transfer. Under certain conditions, dropwise condensation provides for much higher heat transfer rates than filmwise condensation. , Although a drop has a larger surface area than a film occupying the same surface area, this difference is relatively small. At a contact angle of 60°, the ratio of drop surface area to the substrate area occupied by the drop is 1.33.…”

Section: Discussionmentioning

confidence: 99%

“…Drop nucleation, growth, and condensation have important practical consequences. Significantly, heat transfer rates in dropwise condensation can be much higher than in filmwise condensation. , Thus, dropwise condensation is often preferred to filmwise condensation in heat exchangers. , The more general problem of liquid drop interactions on surfaces is of interest for inkjet printing, pesticide application, and spray coating. The rhythmic growth and coalescence of water drops have also been used to construct microscale engines and to pattern sub-micron masks. − …”

Section: Introductionmentioning

confidence: 99%

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Dropwise Condensation: Experiments and Simulations of Nucleation and Growth of Water Drops in a Cooling System

et al. 2006

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Dropwise condensation of water vapor from a naturally cooling, hot water reservoir onto a hydrophobic polymer film and a silanized glass slide was studied by direct observation and simulations. The observed drop growth kinetics suggests that smallest drops grow principally by the diffusion of water adsorbed on the substrate to the drop perimeter, while drops larger than about 50 microm in diameter grow principally by direct deposition from the vapor onto the drop surface. Drop coalescence plays a critical role in determining the drop-size distribution and stimulates the nucleation of new, small drops on the substrates. Simulations of drop growth incorporating these growth mechanisms provide a good description of the observed drop-size distribution. Because of the large role played by coalescence, details of individual drop growth make little difference to the final drop-size distribution. The rate of condensation per unit substrate area is especially high for the smallest drops and may help account for the high heat transfer rates associated with dropwise condensation relative to filmwise condensation in heat exchange applications.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dropwise Condensation: Experiments and Simulations of Nucleation and Growth of Water Drops in a Cooling System

et al. 2006

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“…132 and 16-mercaptohexadecanoic acid that were adsorbed onto gold-coated copper substrates and related the heat transfer coefficient to changes in SAM monolayer thickness and chemistry. The authors found that dropwise condensation formed by using octadecanethiol SAM is a dynamic process in that the heat transfer coefficient decreases with time over 2 h. 135 Vemuri et al used SAMs of n-octadecyl mercaptan and stearic acid on copper alloy surfaces as hydrophobic coatings with the aim of enhancing steam condensation through dropwise condensation. 136 It was found that n-octadecyl mercaptan coated SAM surfaces increased the condensation heat transfer rate by a factor of about 8-times when operated under atmospheric conditions and a theoretical model was developed involving the effect of interfacial heat transfer coefficient on heat transfer rate to calculate the sweeping effect of large falling drops.…”

Section: −139mentioning

confidence: 99%

Anticholinesterase furocoumarins from Heracleum platytaenium, an endemic species to Idea mountains

Dincel¹

2013

Turk J Chem

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Seven different nonlinear height (h)-diameter (d) models were developed and compared for brutian pine (Pinus brutia Ten.), black pine (Pinus nigra Arnold), and Taurus cedar (Cedrus libani A.Rich.) in southern Turkey. Residual analysis was conducted to identify the error structure. A weighting factor of w i =1/d was found to be appropriate for achieving the equal error variance assumption. The performance of the models was compared and evaluated based on 6 statistical criteria and residual analysis. Results suggested that the Gompertz model was superior to the other models in terms of its predictive ability. These tree species were located throughout the Mediterranean region, covering a wide range of topographic and climatic conditions. It is well known that height-diameter relationships depend heavily on local environmental conditions. Differences in the height-diameter relationship among and between ecoregions were tested using the nonlinear extra sum of squares method. Test results suggested that height-diameter models significantly differed between ecoregions, indicating that ecoregion-based height-diameter models are needed for prediction purposes. The ecoregion-based height-diameter models developed in this study may provide more accurate information for developing forest growth and yield models.

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“…Recently, new methods have been introduced to achieve durable hydrophobic coatings on condensing metal surfaces. Modification of substrate surface through coating of self-assembled organic monolayers (SAM) [263][264][265] and Polytetrafluoroethylene (PTFE) 168 have been attempted. For a similar wettability, SAM has been found advantageous over PTFE coatings, because of the low thickness (~30 Å) and associated lower thermal resistance between the condensate and the substrate 266 .…”

Section: Engineered Surfaces For Condensation Heat Transfermentioning

confidence: 99%

Surface engineering for phase change heat transfer: A review

Attinger

Frankiewicz

Betz

et al. 2014

MRS Energy & Sustainability

323

195

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Among numerous challenges to meet the rising global energy demand in a sustainable manner, improving phase change heat transfer has been at the forefront of engineering research for decades. The high heat transfer rates associated with phase change heat transfer are essential to energy and industry applications; but phase change is also inherently associated with poor thermodynamic efficiencies at low heat flux, and violent instabilities at high heat flux. Engineers have tried since the 1930's to fabricate solid surfaces that improve phase change heat transfer. The development of micro and nanotechnologies has made feasible the high-resolution control of surface texture and chemistry over length scales ranging from molecular levels to centimeters. This paper reviews the fabrication techniques available for metallic and siliconbased surfaces, considering sintered and polymeric coatings. The influence of such surfaces in multiphase processes of high practical interest, e.g. boiling, condensation, freezing, and the associated physical phenomena are reviewed. The case is made that while engineers are in principle able to manufacture surfaces with optimum nucleation or thermofluid transport characteristics, more theoretical and experimental efforts are needed to guide the design and cost-effective fabrication of surfaces that not only satisfy the existing technological needs, but also catalyze new discoveries.

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An integrated study of dropwise condensation heat transfer on self-assembled organic surfaces through Fourier transform infra-red spectroscopy and ellipsometry

Cited by 28 publications

References 27 publications

Dropwise Condensation: Experiments and Simulations of Nucleation and Growth of Water Drops in a Cooling System

Dropwise Condensation: Experiments and Simulations of Nucleation and Growth of Water Drops in a Cooling System

Anticholinesterase furocoumarins from Heracleum platytaenium, an endemic species to Idea mountains

Surface engineering for phase change heat transfer: A review

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