DETERMINATION OF DIMENSIONALITY OF POOL BOILING ON A THIN HORIZONTAL DISK UNDER SUBCOOLED CONDTIONS USING THIN-FILM THERMOCOUPLES
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Subcooled pool boiling experiments are conducted at subcooling levels of 10 C on a thin silicon disk ( 400m thickn, 3 inch diameter) with in situ micro-machined K-type thin film thermocouples (TFT) using a perfluorocarbon liquid refrigerant (PF-5060) with a boiling point of 56 C. The experimental apparatus is of constant heat flux type. Surface temperature (from TFT) and heat flux data is obtained at each steady state condition to generate the pool boiling curve. The time delay embedding technique is used to re-construct higher dimensional vectors with the optimal delay being estimated from the first minimum of mutual information. The correlation dimension measure is then estimated from the delay re constructed phase space vectors. In this preliminary study correlation dimension measures are seen to vary from 12 in nucleate boiling, to 7 9 near Critical Heat Flux (CHF) condition, and 7 8 in film boiling. The results suggest that the attractors underlying thermal transport mechanisms in nucleate boiling are affected by a greater number of parameters than that at CHF. The dimension of the attractor is reduced further in the film boiling regime.
