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Influence of surface cavities on pool boiling heat transfer.

Author(s) : LUKE A.

Summary

Characteristic features of the heating surface and bubble formation shall be introduced in calculation methods for the heat transfer in boiling. The microstructure of different prepared steel tubes is measured before and after the heat transfer measurements, which are studied simultaneously with the bubble formation. Different types of microstructure are investigated by a 3-dimensional roughness measurement technique without contact of the stylus with the surface - such as deterministic emery ground surfaces, stochastic sandblasted surfaces and milled surfaces as results of commercial manufacturing processes as well. The method opens the possibility to get more detailed information for the cavities in their 3-dimensional form, as it will be shown by selected examples. The microscopic structure with all its peaks and cavities influences directly the wetting condition of the heated surface by the fluid and therefore the bubble formation and the heat transfer. Therefore the analyse of the surface roughness profiles with an enveloped curve to calculate the size distributions of parameters describing the cavities possibly acting as nucleation sites are transferred to the third dimension. The local distribution of the potential nucleation sites and the size distribution of the cavities are discussed and linked to the size distribution of the active sites in boiling propane. The interaction between the sites is demonstrated by the size distribution of the distances of nearest neighbouring cavities or potential nucleation sites and of the active sites.

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Pages: 2008-2

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Details

  • Original title: Influence of surface cavities on pool boiling heat transfer.
  • Record ID : 2009-0544
  • Languages: English
  • Source: 8th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2008)
  • Publication date: 2008/09/07

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