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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Size Distribution of Active and Potential Nucleation Sites in Pool Boiling

Get access (open in a dialog) DOI: 10.1615/IHTC12.990
6 pages

Resumo

The longterm aim in design of modern evaporators is to find a heat transfer calculation method based on the phenomena of growing and departing vapour bubbles on the heated surface. New developments in computer calculation and in measurement technique support the local analysis of heat transfer, bubble formation and the microstructure of the heated surface. All three kinds of data originate from the same equipment and from experiments performed equallydetailed and preciselyw ith propane boiling on a horizontal copper tube.
The heated surface is treated reproducibly by fine sandblasting. The microstructure of the heated surface is measured byan ultrasonic stylus without contacting the surface, which is studied with bubble formation for two intermediate saturation pressures. The paper focuses on the detailed description of the microstruture by means of statistical analysis of cavities. The local distribution of parameters describing the cavities possibly acting as nucleation sites (potential sites) is calculated by combining the measured topographywith its envelope area. The possible interaction following from the local distribution is discussed. On the other hand, active nucleation sites are localized by high speed videos of bubble formation and are combined with the potential nucleation sites bym eans of statistical methods.