Abstract

The film coefficient of heat transfer from a hot metal surface to a boiling liquid was estimated from experiments with an electrically heated wire submerged in the liquid. The heat-flow rate was given by the consumption of electric power. The temperature drop through the film was taken as the difference between the surface temperature of the wire and the mean temperature of the liquid. The surface temperature of the wire was estimated by a small thermocouple. The graph of film coefficient, as a function of temperature drop through the film, is called the “boiling” curve. As the temperature drop increased, the film coefficient first rose to a maximum, then fell to a minimum, from which it rose steadily as the temperature drop continued to increase. When water was boiled at atmospheric pressure, different heated metals gave different boiling curves. Preliminary data are given for nickel, tungsten, chromel A, and chromel C. When water was boiled at different elevated pressures, the same heated metal gave different boiling curves. The data are given for nickel and chromel at 0, 25, 50, 75, and 100 psig. Throughout these experiments the general form of the boiling curve remains the same.

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