Boiling Nucleation on Very Small Film Heater Subjected to Extremely Rapid Heating

Abstract

A very small film heater with an area of 0.1×0.25 mm², which is immersed in either water, ethyl alcohol or toluene, is heated with an extremely high rate of temperature rise of 93×10⁶ K/s at the maximum. The aspect of nucleation is photographed and the temperature of boiling incipience is measured versus the rate of temperature rise. Under the condition of high rise rate, a large number of tiny bubbles are formed concurrently on the heater surface, and the temperature of boiling incipience becomes constant and almost equal to the theoretical homogeneous nucleation temperature for ethyl alcohol and toluene, whereas it is about 19 K lower than the theoretical one for water. The number density of the nucleated bubbles is measured and compared with that calculated by the nucleation theory. The maximum number density of bubbles is plotted versus the rate of temperature rise. The phenomenon observed at a high rate of rise is concluded to be due to fluctuation nucleation.