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International Heat Transfer Conference 13

ISBN Imprimir: 1-56700-226-9 (CD)
ISBN En Línea: 1-56700-225-0


DOI: 10.1615/IHTC13.p28.270
page 12

A. Luke
Institut für Thermodynamik Universität Hannover, Hannover, Germany


The surface structure, heat transfer and active nucleation sites on horizontal copper tubes are investigated. The surface of the tubes of varying diameter is fine sandblasted resulting in a stochastic microstructure. The surfaces are measured by a three-dimensional contactless stylus instrument combining the stylus technique with the near field acoustic microscopy. The method opens the possibility to obtain results according to standard for practical belongings on the one side and to get detailed information about the three-dimensional shape of each cavity within the surface investigated on the other side. The heat transfer measurements are carried out with R134a, propane and 2-propanol in wide ranges of pressure and heat flux within the standard apparatus. The bubble formation is observed by high speed video technique. The active nucleation sites are localized and are combined with the potential nucleation sites by means of statistical methods. The differences between simultaneously activated nucleation sites are manifold. The heat transfer coefficients for the three fluids are nearly the same although the bubble formation is totally different.

IHTC-13 Digital Library

Measurement of fluid temperature with an arrangement of three thermocouples FLOW BOILING OF A HIGHLY VISCOUS POLYMER SOLUTION