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    Item type:Publication, Access status: without files ,
    An extended similarity theory applied to heated flows in complex geometries
    (2009-05-04)
    Bünger, Florian
    ;
    Herwig, Heinz
    In the traditional similarity theory the influence of temperature- and pressure-dependent fluid properties on the flow field and heat transfer is not described by the basic dimensionless parameters, i.e. Prandtl, Reynolds, Rayleigh,... number. We present an extended similarity theory that not only takes into account the variable material properties but also can handle small variations in other parameters of the physical model like small changes in the (reference) Prandtl number. The method has general applicability that is suitable for a wide variety of fluid dynamic and heat transfer situations in which variable properties with a strong dependence on temperature and pressure play a significant role. It is especially useful in predicting the behaviour of a certain fluid based on the results for a different one. As an example the Nußelt number of a lid driven heated cavity is determined with fluid properties being temperature dependent.
    Publicationtype: Journal Article
      71
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    Item type:Publication, Access status: without files ,
    Micro channel roughness effects : a close-up view
    (American Society of Mechanical Engineers (ASME), 2007)
    Gloss, Daniel
    ;
    Köcke, I.
    ;
    Herwig, Heinz
    The effect of wall roughness on laminar flows may be important in micro sized channels though it is often neglected in macro sized flow geometries. Based on entropy production considerations we show how its influence can be determined theoretically. It is also discussed how different ways to define the actual wall location influence the pressure drop results in terms of a Poiseuille number.
    Publicationtype: Conference Paper
      11