| Titre : |
The effect of drainage on condensation heat transfer |
| Type de document : |
texte imprimé |
| Auteurs : |
Z. L. Aidoun, Auteur ; A. A. Nicol, Directeur de thèse |
| Editeur : |
Ecosse : University of Strathclyde |
| Année de publication : |
1984 |
| Importance : |
255 f. |
| Présentation : |
ill. |
| Format : |
30 cm. |
| Note générale : |
Thèse de Doctorat : Génie Mécanique : Ecosse, University of Strathclyde : 1984
Annexe f. 257 - 365 . - Bibliogr. f. 366 - 375 |
| Langues : |
Anglais (eng) |
| Mots-clés : |
Heat transfer
Condenser tube
Water issuing
Drainage patterns |
| Index. décimale : |
D003884 |
| Résumé : |
The experimental and theoretical investigation of the effect of condensate inundation on the heat transfer coefficient of a quiescent vapour condensing on a horizontal condenser tube is reported. Simulated condensation studies have been made using water issuing through a row of small holes drilled along the top of a 28 mm 0.D. copper tube. Adjacent holes were close enough to ensure that a continuous film formed over the whole surface. The drainage mechanism from this tube and also from a second tube, located below, was studied by analysing individual frames on a film taken with a high speed camera. Drainage patterns were studied for a range of water flowrates and the number of drainage sites, drop sizes and frequencies were determined. Additional tests were made with freon 113, water-Teepol and water-Glycerol mixtures to investigate the effets of surface tension and viscosity on the drainage patterns.
Drainage behaviour was shown to be markedly dependent on surface tension but relatively insensitive to viscosity.
Experiments under real actual condensation conditions have also been carried out on a row of 3 tubes 19.05 mm 0D, 16.53 mm ID and 300 mm length located in a glass condenser to allow for visual observation. In these experiments condensate drainage was increased by recycling part of the condensate collected at the bottom of the condenser through a fourth tube located above the test row and drilled with small holes along the top. The range of mass flowrates recycled was 0 - 70.56 g/s. The pressures and velocities used were respectively 0.20 - 0.66 bar and 0.321 - 1.389 m/s. Average values of overall heat transfer coefficient were obtained in the range 1.653 - 4.061 kW/m²K. Values of steamside heat transfer coefficient were also obtained in the range 4 - 16 kW/m²K.
The results were compared with existing correlations, the Nusselt theory for drainage and with a theoretical analysis developed in this thesis based on thin film considerations. The experimental and theoretical results show that for condensation with inundation the heat transfer coefficient decreases with increasing film Reynolds Number. The influence of the cooling water on the heat transfer coefficient is also shown to be appreciable. |
The effect of drainage on condensation heat transfer [texte imprimé] / Z. L. Aidoun, Auteur ; A. A. Nicol, Directeur de thèse . - Ecosse : University of Strathclyde, 1984 . - 255 f. : ill. ; 30 cm. Thèse de Doctorat : Génie Mécanique : Ecosse, University of Strathclyde : 1984
Annexe f. 257 - 365 . - Bibliogr. f. 366 - 375 Langues : Anglais ( eng)
| Mots-clés : |
Heat transfer
Condenser tube
Water issuing
Drainage patterns |
| Index. décimale : |
D003884 |
| Résumé : |
The experimental and theoretical investigation of the effect of condensate inundation on the heat transfer coefficient of a quiescent vapour condensing on a horizontal condenser tube is reported. Simulated condensation studies have been made using water issuing through a row of small holes drilled along the top of a 28 mm 0.D. copper tube. Adjacent holes were close enough to ensure that a continuous film formed over the whole surface. The drainage mechanism from this tube and also from a second tube, located below, was studied by analysing individual frames on a film taken with a high speed camera. Drainage patterns were studied for a range of water flowrates and the number of drainage sites, drop sizes and frequencies were determined. Additional tests were made with freon 113, water-Teepol and water-Glycerol mixtures to investigate the effets of surface tension and viscosity on the drainage patterns.
Drainage behaviour was shown to be markedly dependent on surface tension but relatively insensitive to viscosity.
Experiments under real actual condensation conditions have also been carried out on a row of 3 tubes 19.05 mm 0D, 16.53 mm ID and 300 mm length located in a glass condenser to allow for visual observation. In these experiments condensate drainage was increased by recycling part of the condensate collected at the bottom of the condenser through a fourth tube located above the test row and drilled with small holes along the top. The range of mass flowrates recycled was 0 - 70.56 g/s. The pressures and velocities used were respectively 0.20 - 0.66 bar and 0.321 - 1.389 m/s. Average values of overall heat transfer coefficient were obtained in the range 1.653 - 4.061 kW/m²K. Values of steamside heat transfer coefficient were also obtained in the range 4 - 16 kW/m²K.
The results were compared with existing correlations, the Nusselt theory for drainage and with a theoretical analysis developed in this thesis based on thin film considerations. The experimental and theoretical results show that for condensation with inundation the heat transfer coefficient decreases with increasing film Reynolds Number. The influence of the cooling water on the heat transfer coefficient is also shown to be appreciable. |
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