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A study of the nucleate boiling heat transfer coefficient of dichlorodifluoremethane (Freon-12) over a horizontal surface Tang, Shih-I


The heat transfer coefficients for oil-free liquid dichlorodifluoromethane (Preon-12 or Genetron-12) in nucleate boiling over a horizontal copper surface were measured at saturation temperatures of 0°F and 25°F and at heat flux densities between 6,000 and 63,000 Btu/hr-ft². The heating surfaces were finished with 400-A emery paper in two different patterns before each series of test-runs, while the geometric arrangement and the other parameters of the apparatus remained unchanged. Profilometer measurements of roughness and photomicrographs of the surface were taken. All the boiling curves calculated and plotted from the experimental results were of "S" shape, revealing a pronounced deviation from the conventional (normal) boiling curve, especially at lower saturation temperatures. The deviation of the boiling curve was probably due to the unpredictable nucleating characteristics of the heating surface and of the bubble population [1, 2]. This makes it impossible to correlate the experimental data by any of the existing empirical equations formulated by Zuber [3, 4, 5], Rohsenow [6, 7], Levy [16] and others.

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