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Dropwise condensation modeling suitable for superhydrophobic surfaces / Sunwoo Kim in Journal of heat transfer, Vol. 133 N° 8 (Août 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 8 (Août 2011) . - pp. [081502/1-8] Titre : Dropwise condensation modeling suitable for superhydrophobic surfaces Type de document : texte imprimé Auteurs : Sunwoo Kim, Auteur ; Kwang J. Kim, Auteur Année de publication : 2011 Article en page(s) : pp. [081502/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Dropwise  condensation  Contact  angle  Hydrophobicity  Surface  wettability  Drop  size  distribution Index. décimale : 536 Chaleur. Thermodynamique Résumé : A mathematical model is developed to represent and predict the dropwise condensation phenomenon on nonwetting surfaces having hydrophobic or superhydrophobic (contact angle greater than 150 deg) features. The model is established by synthesizing the heat transfer through a single droplet with the drop size distribution. The single droplet heat transfer is analyzed as a combination of the vapor-liquid interfacial resistance, the resistance due to the conduction through the drop itself, the resistance from the coating layer, and the resistance due to the curvature of the drop. A population balance model is adapted to develop a drop distribution function for the small drops that grow by direct condensation. Drop size distribution for large drops that grow mainly by coalescence is obtained from a well-known empirical equation. The evidence obtained suggests that both the single droplet heat transfer and drop distribution are significantly affected by the contact angle. More specifically, the model results indicate that a high drop-contact angle leads to enhancing condensation heat transfer. Intense hydrophobicity, which produces high contact angles, causes a reduction in the size of drops on the verge of falling due to gravity, thus allowing space for more small drops. The simulation results are compared with experimental data, which were previously reported. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...] [article] Dropwise condensation modeling suitable for superhydrophobic surfaces [texte imprimé] / Sunwoo Kim, Auteur ; Kwang J. Kim, Auteur . - 2011 . - pp. [081502/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 8 (Août 2011) . - pp. [081502/1-8] Mots-clés : Dropwise  condensation  Contact  angle  Hydrophobicity  Surface  wettability  Drop  size  distribution Index. décimale : 536 Chaleur. Thermodynamique Résumé : A mathematical model is developed to represent and predict the dropwise condensation phenomenon on nonwetting surfaces having hydrophobic or superhydrophobic (contact angle greater than 150 deg) features. The model is established by synthesizing the heat transfer through a single droplet with the drop size distribution. The single droplet heat transfer is analyzed as a combination of the vapor-liquid interfacial resistance, the resistance due to the conduction through the drop itself, the resistance from the coating layer, and the resistance due to the curvature of the drop. A population balance model is adapted to develop a drop distribution function for the small drops that grow by direct condensation. Drop size distribution for large drops that grow mainly by coalescence is obtained from a well-known empirical equation. The evidence obtained suggests that both the single droplet heat transfer and drop distribution are significantly affected by the contact angle. More specifically, the model results indicate that a high drop-contact angle leads to enhancing condensation heat transfer. Intense hydrophobicity, which produces high contact angles, causes a reduction in the size of drops on the verge of falling due to gravity, thus allowing space for more small drops. The simulation results are compared with experimental data, which were previously reported. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...]

Dynamic surface tension of heat transfer additives suitable for use in steam condensers and absorbers / Yong-Du Jun in International journal of refrigeration, Vol. 33 N° 2 (Mars 2010) 

Public ISBD [article]  in International journal of refrigeration > Vol. 33 N° 2 (Mars 2010) . - pp. 428-434 Titre : Dynamic surface tension of heat transfer additives suitable for use in steam condensers and absorbers Titre original : Tension superficielle dynamique des additifs favorisant le transfert de chaleur adaptés à l’utilisation dans les condenseurs de vapeur et les absorbeurs Type de document : texte imprimé Auteurs : Yong-Du Jun, Auteur ; Kwang J. Kim, Auteur ; John M. Kennedy, Auteur Année de publication : 2011 Article en page(s) : pp. 428-434 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Heat  exchanger  Absorber  Condenser  Measurement  Surface  tension  Additive  Heat  transfer Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Additives are often effectively used in enhancing heat transfer by creating a surface tension gradient on the surface of a condensate film to induce Marangoni driven “dropwise-like” condensation. The objective of the current study is to use the Maximum Bubble Pressure Method (MBPM) to evaluate dynamic behavior of the surface tension of solutions of three different additives (2-ethoxy ethanol, isobutylamine, and 2-ethyl-1-hexanol) of varying concentrations with water. It was shown that the effects of 2-ethoxy ethanol on surface tension was primarily dependent on solute concentration and showed little dependence on time (i.e. surface age of bubble). While both isobutylamine and 2-ethyl-1-hexanol showed strong dependence on both concentration and time, the effects of the later were far more dramatic. The results for all solutions are presented as functions of concentration and time (i.e. surface age of bubble). DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700709002667 [article] Dynamic surface tension of heat transfer additives suitable for use in steam condensers and absorbers = Tension superficielle dynamique des additifs favorisant le transfert de chaleur adaptés à l’utilisation dans les condenseurs de vapeur et les absorbeurs [texte imprimé] / Yong-Du Jun, Auteur ; Kwang J. Kim, Auteur ; John M. Kennedy, Auteur . - 2011 . - pp. 428-434. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 2 (Mars 2010) . - pp. 428-434 Mots-clés : Heat  exchanger  Absorber  Condenser  Measurement  Surface  tension  Additive  Heat  transfer Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Additives are often effectively used in enhancing heat transfer by creating a surface tension gradient on the surface of a condensate film to induce Marangoni driven “dropwise-like” condensation. The objective of the current study is to use the Maximum Bubble Pressure Method (MBPM) to evaluate dynamic behavior of the surface tension of solutions of three different additives (2-ethoxy ethanol, isobutylamine, and 2-ethyl-1-hexanol) of varying concentrations with water. It was shown that the effects of 2-ethoxy ethanol on surface tension was primarily dependent on solute concentration and showed little dependence on time (i.e. surface age of bubble). While both isobutylamine and 2-ethyl-1-hexanol showed strong dependence on both concentration and time, the effects of the later were far more dramatic. The results for all solutions are presented as functions of concentration and time (i.e. surface age of bubble). DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700709002667